Overview of Metabolism
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Questions and Answers

What is the main focus of metabolism in living organisms?

  • Genetic information processing
  • Growth and reproduction
  • Cellular structure and function
  • Storage and transfer of energy (correct)

    • Which statement accurately describes the role of enzymes in metabolic reactions?

  • Every reaction in cells requires multiple enzymes.
  • Enzymes speed the rates of biological reactions and are highly regulated. (correct)
  • Enzymes are consumed during reactions and cannot be reused.
  • Enzymes are only produced during starvation.

    • How is metabolism classified?

  • Into catabolism and anabolism (correct)
  • By the type of energy utilized
  • By the number of reactions involved
  • Into structural and dynamic processes

    • What is catabolism primarily responsible for?

    <p>Conversion of complex biomolecules into simpler products</p> Signup and view all the answers

    What distinguishes anabolic pathways from catabolic pathways?

    <p>Anabolic pathways create complex molecules; catabolic pathways break them down.</p> Signup and view all the answers

    Which type of biomolecules typically yields energy during catabolic pathways?

    <p>Carbohydrates, proteins, and lipids</p> Signup and view all the answers

    Which of the following statements about catabolic pathways is false?

    <p>They produce energy in all cases.</p> Signup and view all the answers

    What is a significant characteristic of enzymes in metabolic reactions?

    <p>Enzymes can catalyze reactions without being consumed.</p> Signup and view all the answers

    What is the main function of NADP+ in metabolic processes?

    <p>It serves as a coenzyme in oxidation and reduction reactions.</p> Signup and view all the answers

    In catabolic metabolism, what is primarily produced?

    <p>Chemical energy from oxidized compounds.</p> Signup and view all the answers

    What is the maximum energy released from burning one mole of glucose?

    <p>687 kcal of energy.</p> Signup and view all the answers

    How do living organisms differ from a bomb calorimeter in energy release from glucose oxidation?

    <p>They trap a portion of energy as chemical energy.</p> Signup and view all the answers

    What percentage of energy released from glucose oxidation is approximately captured as ATP in living organisms?

    <p>30 percent.</p> Signup and view all the answers

    What process do living organisms utilize to convert carbon dioxide into more reduced compounds?

    <p>Anabolism.</p> Signup and view all the answers

    What main advantage do living organisms have over simple combustion processes in terms of energy?

    <p>They can utilize energy efficiently for growth.</p> Signup and view all the answers

    What role does oxidation play in the catabolic pathways of organisms?

    <p>It generates chemical energy from reduced compounds.</p> Signup and view all the answers

    What is the primary focus of catabolic pathways?

    <p>Production of energy-rich intermediates</p> Signup and view all the answers

    How do anabolic pathways primarily generate energy?

    <p>By employing ATP as an energy source</p> Signup and view all the answers

    Which molecule is primarily used as a reducing agent in anabolic pathways?

    <p>NADPH</p> Signup and view all the answers

    What type of products do anabolic pathways yield compared to their starting materials?

    <p>More reduced products</p> Signup and view all the answers

    What is a key feature of catabolic pathways is in terms of energy?

    <p>They generate heat as a byproduct.</p> Signup and view all the answers

    What type of starting materials are used in catabolic pathways?

    <p>Reduced organic compounds such as lipids, carbohydrates, and amino acids</p> Signup and view all the answers

    What is the average amount of energy reserves in an average human in the form of carbohydrate as glycogen?

    <p>1500 kcal</p> Signup and view all the answers

    What is a defining characteristic of anabolic pathways compared to catabolic pathways?

    <p>They synthesize complex biomolecules from simpler ones.</p> Signup and view all the answers

    In what scenario would a metabolic pathway run backwards?

    <p>If it does not release some heat</p> Signup and view all the answers

    During starvation, which type of protein is primarily scavenged for energy?

    <p>Muscle protein</p> Signup and view all the answers

    What is the main output product of energy production in humans used for excreting excess nitrogen?

    <p>Urea</p> Signup and view all the answers

    How many kcal must be burned to lose one pound of body weight?

    <p>3500 kcal</p> Signup and view all the answers

    In which context is pyruvate converted to acetylCoA?

    <p>Under aerobic conditions</p> Signup and view all the answers

    What is the primary role of NADH in the TCA cycle?

    <p>To create a proton gradient</p> Signup and view all the answers

    The primary source of stored fat in humans is found as what?

    <p>Triglycerols</p> Signup and view all the answers

    Which major organ is responsible for converting lactic acid to glucose?

    <p>Liver</p> Signup and view all the answers

    What is released upon the hydrolysis of the terminal phosphates in ATP?

    <p>High amounts of energy</p> Signup and view all the answers

    Which part of ATP hydrolysis serves as a source of energy input for other biochemical reactions?

    <p>Hydrolysis of the terminal phosphoanhydride bonds</p> Signup and view all the answers

    What type of bond links the terminal phosphates in ATP?

    <p>Phosphoanhydride bonds</p> Signup and view all the answers

    Why is glucose phosphorylation considered a coupled reaction?

    <p>It couples an unfavorable reaction with a favorable one.</p> Signup and view all the answers

    What is the ΔG of the reaction that combines glucose and Pi to form glucose-6-P?

    <p>+13.9 kJ/mol</p> Signup and view all the answers

    What is necessary for the synthesis of ATP?

    <p>Energy input from catabolic reactions</p> Signup and view all the answers

    Which enzyme catalyzes the phosphorylation of glucose in glycolysis?

    <p>Hexokinase</p> Signup and view all the answers

    What happens during the hydrolysis of the phosphoanhydride bonds in ATP?

    <p>Releases energy for cellular work</p> Signup and view all the answers

    What type of bond links the terminal phosphates in ATP?

    <p>Phosphoanhydride bonds</p> Signup and view all the answers

    Which of the following statements accurately describes the energy released during ATP hydrolysis?

    <p>It provides energy input for other biochemical reactions.</p> Signup and view all the answers

    What is the ΔG value associated with the hydrolysis of ATP to ADP?

    <p>-30.5 kJ/mol</p> Signup and view all the answers

    What occurs when a thermodynamically unfavorable reaction is coupled with a thermodynamically favorable one?

    <p>The overall reaction can have a negative ΔG.</p> Signup and view all the answers

    Which of the following best describes the role of hexokinase in glycolysis?

    <p>It catalyzes glucose phosphorylation.</p> Signup and view all the answers

    How is ATP synthesized?

    <p>By coupling the release of energy from catabolic reactions.</p> Signup and view all the answers

    Which phosphate in ATP is responsible for transferring energy to other molecules?

    <p>Gamma phosphate</p> Signup and view all the answers

    What is the energy release upon hydrolysis of ATP linked to?

    <p>The breaking of phosphoanhydride bonds.</p> Signup and view all the answers

    What is the primary result of catabolism in metabolic processes?

    <p>Production of chemical energy</p> Signup and view all the answers

    How does the oxidation of glucose in a living organism differ from that in a bomb calorimeter?

    <p>Heat production is minimized in the organism</p> Signup and view all the answers

    What approximate percentage of the energy released from glucose oxidation is used to form ATP in living organisms?

    <p>30 percent</p> Signup and view all the answers

    What role does NADH play in cellular energy production?

    <p>It supplies high energy electrons to the electron transport system.</p> Signup and view all the answers

    What type of compound is primarily reduced during anabolic pathways?

    <p>Carbon dioxide</p> Signup and view all the answers

    How does NADP+ differ from NAD+ in terms of structure?

    <p>NADP+ contains an extra phosphate group on the ribose ring.</p> Signup and view all the answers

    What occurs during the combustion of one mole of glucose?

    <p>Heat is released as energy</p> Signup and view all the answers

    During the oxidation of NAD+ to NADH, which of the following occurs?

    <p>NAD+ gains two electrons and a proton.</p> Signup and view all the answers

    Which molecule is characterized by having an extra phosphate residue on its ribose ring structure?

    <p>NADP+</p> Signup and view all the answers

    What is the primary purpose of catabolic pathways in terms of energy?

    <p>To capture energy for short-term storage</p> Signup and view all the answers

    What is the primary function of NADPH in metabolic processes?

    <p>To provide reducing power for anabolic reactions.</p> Signup and view all the answers

    What is the consequence of the proton gradient generated by NADH oxidation?

    <p>It drives the activity of ATPase to generate ATP.</p> Signup and view all the answers

    What would be the main difference in metabolism between a bomb calorimeter and a living organism?

    <p>Living organisms can store released energy</p> Signup and view all the answers

    Which statement best describes the enzymatic activity related to NAD+ and NADP+?

    <p>NAD+ functions as an oxidant while NADP+ typically serves as a reductant.</p> Signup and view all the answers

    What is the relationship between NADH and the electron transport chain?

    <p>NADH is oxidized, donating high energy electrons to the chain.</p> Signup and view all the answers

    Which components are involved in the enzymatic activity of NAD+ and NADP+?

    <p>The riboses, phosphates, and the adenine base.</p> Signup and view all the answers

    What energy source do muscles primarily use during activity?

    <p>Primarily fats and carbohydrates</p> Signup and view all the answers

    What is the main function of phosphocreatine in energy metabolism?

    <p>To serve as a backup storage form of high energy phosphate</p> Signup and view all the answers

    Which mechanism is NOT involved in regulating metabolic activity?

    <p>Random mutation of genes</p> Signup and view all the answers

    In a marathon, which energy sources are primarily used?

    <p>Aerobic metabolism of glucose and fatty acids</p> Signup and view all the answers

    What happens to the rate of energy production as the quantity of energy source increases?

    <p>The rate increases inversely</p> Signup and view all the answers

    What type of regulation directly alters enzyme activity through metabolite interaction?

    <p>Allosteric regulation</p> Signup and view all the answers

    What is the maximum ATP equivalent from stored fatty acids?

    <p>4,000,000 mmol</p> Signup and view all the answers

    What is regulated through cellular compartmentalization?

    <p>Expression of specific metabolic activities in certain areas</p> Signup and view all the answers

    Which form of energy reserve is most abundant in an average human?

    <p>Fat as triglycerols</p> Signup and view all the answers

    What is the primary energy-rich product generated during the TCA cycle?

    <p>NADH</p> Signup and view all the answers

    During starvation, which protein source can be scavenged for energy?

    <p>Muscle protein</p> Signup and view all the answers

    What process integrates glycerol into energy production?

    <p>Glycolysis</p> Signup and view all the answers

    What quantity of kcal must be burned to lose one pound of body weight?

    <p>3500 kcal</p> Signup and view all the answers

    What is a major functional role of the liver in energy metabolism?

    <p>Conversion of lactic acid to glucose</p> Signup and view all the answers

    Which of the following best describes the role of pyruvate in metabolism?

    <p>It can serve as a precursor for carbohydrates.</p> Signup and view all the answers

    What is the primary output product of human energy production that helps remove excess nitrogen?

    <p>Urea</p> Signup and view all the answers

    What type of bond connects the terminal phosphates in ATP?

    <p>Phosphoanhydride bonds</p> Signup and view all the answers

    What is the approximate energy released upon hydrolysis of ATP's terminal phosphates?

    <p>7.3 kcal per mole</p> Signup and view all the answers

    Which reaction exemplifies a coupled reaction involving ATP?

    <p>Phosphorylation of glucose to glucose-6-P</p> Signup and view all the answers

    What must occur for the synthesis of ATP to take place?

    <p>Coupling with a favorable reaction</p> Signup and view all the answers

    Which enzyme catalyzes the phosphorylation of glucose in the glycolysis pathway?

    <p>Hexokinase</p> Signup and view all the answers

    Which bond in ATP is associated with a lower energy release upon hydrolysis?

    <p>Phosphoester bond with α phosphate</p> Signup and view all the answers

    Which of the following statements about coupled reactions is true?

    <p>They involve shared intermediates.</p> Signup and view all the answers

    What is the overall ΔG when glucose is phosphorylated by ATP?

    <p>Negative 16.6 kJ/mol</p> Signup and view all the answers

    Which statement accurately describes the primary role of NADH in cellular processes?

    <p>It serves as a major electron donor in oxidative phosphorylation.</p> Signup and view all the answers

    How does the structure of NADP+ differ from that of NAD+?

    <p>NADP+ contains a phosphate group on the ribose ring.</p> Signup and view all the answers

    In which process is NADH primarily oxidized to release energy?

    <p>Electron transport chain</p> Signup and view all the answers

    What is the role of NADPH in metabolic pathways?

    <p>It donates protons and electrons in anabolic reactions.</p> Signup and view all the answers

    What occurs to the nicotinamide ring of NAD+ during its reduction to NADH?

    <p>It gains two electrons and a proton.</p> Signup and view all the answers

    What is the result of high-energy electrons from NADH passing through the electron transport system?

    <p>They create a proton gradient used for ATP synthesis.</p> Signup and view all the answers

    Which of the following statements correctly highlights the function of NAD+ in metabolic reactions?

    <p>NAD+ primarily serves as an oxidant in catabolic reactions.</p> Signup and view all the answers

    Which statement best describes the relationship between NAD+ and NADH in metabolism?

    <p>NAD+ is reduced to NADH, which is then used for generating ATP in catabolic pathways.</p> Signup and view all the answers

    What is the main energy source for the brain?

    <p>Blood glucose</p> Signup and view all the answers

    Which metabolic process is primarily used during a marathon?

    <p>Aerobic metabolism</p> Signup and view all the answers

    How does allosteric regulation affect enzyme activity?

    <p>By directly activating or inhibiting enzyme activity</p> Signup and view all the answers

    What is the role of creatine kinase in metabolism?

    <p>It catalyzes the transfer of high energy phosphate</p> Signup and view all the answers

    What percentage of human carbohydrate reserves is stored in muscle as glycogen?

    <p>75%</p> Signup and view all the answers

    Which statement about phosphocreatine is true?

    <p>It acts as a backup storage for high energy phosphate.</p> Signup and view all the answers

    Which mechanism allows specific metabolic activities to be localized within cells?

    <p>Cellular compartmentalization</p> Signup and view all the answers

    What is the approximate maximum running velocity for sprinting, according to metabolic profiles?

    <p>25 miles per hour</p> Signup and view all the answers

    What is the primary source of energy reserves in the form of fat in an average human?

    <p>135,000 kcal</p> Signup and view all the answers

    Under aerobic conditions, pyruvate is converted into what compound in the energy production pathways?

    <p>AcetylCoA</p> Signup and view all the answers

    Which molecule is primarily produced and utilized for energy in the TCA cycle?

    <p>NADH</p> Signup and view all the answers

    What process does the liver perform regarding carbohydrate storage?

    <p>Stores carbohydrates as glycogen</p> Signup and view all the answers

    What is the primary role of triglycerols in human metabolism?

    <p>Storing fat in adipose tissue</p> Signup and view all the answers

    What is required for a human to lose one pound of body weight in terms of caloric expenditure?

    <p>3500 kcal</p> Signup and view all the answers

    What happens to proteins during periods of starvation in humans?

    <p>Muscle proteins can be scavenged for energy.</p> Signup and view all the answers

    How many kcal does an average human utilize daily, depending on exercise level?

    <p>1500-2500 kcal</p> Signup and view all the answers

    What is the main characteristic of catabolic pathways in metabolism?

    <p>They convert complex biomolecules into simpler products.</p> Signup and view all the answers

    Which of the following statements about enzyme catalysis is accurate?

    <p>Enzymes are essential for speeding up biological reactions.</p> Signup and view all the answers

    What does the term anabolism specifically refer to in metabolic processes?

    <p>The process of converting simple molecules into complex ones.</p> Signup and view all the answers

    Which of the following describes the energy generation in catabolic pathways for biomolecules with a high percentage of carbon?

    <p>They primarily release energy.</p> Signup and view all the answers

    How are catabolic pathways primarily characterized in terms of chemical reactions?

    <p>They are usually degradative and involve oxidation.</p> Signup and view all the answers

    What type of biomolecules typically produce little or no energy during catabolic pathways?

    <p>Nucleotides.</p> Signup and view all the answers

    What is the outcome of metabolic pathways that convert complex biomolecules into simpler products?

    <p>Production of energy-rich compounds.</p> Signup and view all the answers

    What is a significant feature defining the metabolic pathways of living organisms?

    <p>They involve continuous and regulated enzyme-catalyzed reactions.</p> Signup and view all the answers

    Which pathway is primarily responsible for the conversion of glucose to pyruvate?

    <p>Glycolysis</p> Signup and view all the answers

    What is the primary energy-rich product generated during the TCA cycle?

    <p>NADH</p> Signup and view all the answers

    Which macromolecule serves as a primary energy reserve for the human body?

    <p>Fats</p> Signup and view all the answers

    Which organ is primarily responsible for regulating blood levels of metabolites and converting lactic acid to glucose?

    <p>Liver</p> Signup and view all the answers

    What is a major output product formed from the catabolism of proteins?

    <p>Urea</p> Signup and view all the answers

    During starvation, which type of bodily protein is primarily utilized for energy?

    <p>Muscle proteins</p> Signup and view all the answers

    What is the average daily energy expenditure for an average human?

    <p>1500-2500 kcal</p> Signup and view all the answers

    How many kcal must be burned to achieve a weight loss of one pound?

    <p>3500 kcal</p> Signup and view all the answers

    What is the main effect of catabolic pathways on energy production?

    <p>They oxidize highly hydrogenated compounds to produce chemical energy.</p> Signup and view all the answers

    What is a significant characteristic of the sequential oxidation of carbon in metabolic processes?

    <p>It results in the stepwise conversion of compounds into carbon dioxide.</p> Signup and view all the answers

    How does the energy captured by living organisms during the oxidation of glucose compare to that released in a bomb calorimeter?

    <p>Living organisms capture approximately 30% of the energy as chemical energy.</p> Signup and view all the answers

    Which statement correctly describes the energy relationships of ATP hydrolysis and glucose phosphorylation?

    <p>ATP hydrolysis serves as an energy source for the endergonic phosphorylation of glucose.</p> Signup and view all the answers

    What is the impact of a bomb calorimeter on understanding glucose oxidation?

    <p>It provides a measure of energy converted from glucose to carbon dioxide.</p> Signup and view all the answers

    What is the approximate energy released per mole upon hydrolysis of the terminal phosphoanhydride bonds in ATP?

    <p>7.3 kcal</p> Signup and view all the answers

    In the coupled reaction of glucose phosphorylation, what is the combined ΔG for the overall reaction?

    <p>-16.6 kJ/mol</p> Signup and view all the answers

    Which statement accurately reflects the differences in compound states during catabolism and anabolism?

    <p>Anabolism synthesizes macromolecules from reduced starting materials.</p> Signup and view all the answers

    Which type of bond links the α phosphate in ATP to the first carbon atom in glucose-6-phosphate?

    <p>Phosphoester bond</p> Signup and view all the answers

    In the context of metabolism, what role does NADP+ primarily serve?

    <p>It provides reducing power in both catabolic and anabolic pathways.</p> Signup and view all the answers

    What role does hexokinase play in the phosphorylation of glucose?

    <p>It transfers the γ phosphate from ATP to glucose.</p> Signup and view all the answers

    What is the significance of the extra phosphate residue on C-2’ of the ribose ring in NADP+?

    <p>It allows NADP+ to act as an electron acceptor in metabolic reactions.</p> Signup and view all the answers

    What is the primary energy form produced as a result of catabolic processes?

    <p>Chemical energy stored in ATP primarily.</p> Signup and view all the answers

    Which reaction would not participate in coupling with ATP hydrolysis?

    <p>A process with a negative ΔG</p> Signup and view all the answers

    Which of the following would be true about the hydrolysis of phosphoanhydride bonds in ATP?

    <p>It provides energy for thermodynamically unfavorable reactions.</p> Signup and view all the answers

    What type of reaction does the catabolism of reduced organic compounds primarily involve?

    <p>Release of energy through oxidation</p> Signup and view all the answers

    What primarily drives anabolic pathways in terms of energy requirements?

    <p>Direct use of ATP</p> Signup and view all the answers

    Which product is typically generated from catabolic pathways?

    <p>Acetyl-CoA</p> Signup and view all the answers

    Which statement correctly describes the outcome of anabolic pathways?

    <p>They use NADPH as a reducing agent.</p> Signup and view all the answers

    In which scenario would anabolic reactions primarily be favored?

    <p>When simple building blocks are abundantly available</p> Signup and view all the answers

    What role does NADH play in catabolic pathways?

    <p>It is converted to ATP through oxidative phosphorylation.</p> Signup and view all the answers

    Which statement is accurate regarding the connection between catabolic and anabolic pathways?

    <p>They are distinct but interconnected reactions.</p> Signup and view all the answers

    What key factor limits the reverse operation of metabolic pathways?

    <p>The release of heat in every pathway and reaction</p> Signup and view all the answers

    Which type of biomolecule synthesis is typical of anabolic pathways?

    <p>Formation of complex molecules from simple units</p> Signup and view all the answers

    What mechanism allows for the direct activation or inhibition of enzyme activity by various metabolites?

    <p>Allosteric regulation</p> Signup and view all the answers

    Which substance primarily serves as a backup storage form of high-energy phosphate in muscle tissue?

    <p>Phosphocreatine</p> Signup and view all the answers

    During a marathon, which primary energy source is utilized by the body?

    <p>Glycogen and fatty acids</p> Signup and view all the answers

    How does the availability of stored fatty acids compare to ATP in terms of total ATP equivalents?

    <p>Stored fatty acids provide significantly more ATP than ATP itself.</p> Signup and view all the answers

    What type of metabolic regulation involves cellular responses to changes in energy demands?

    <p>Gene expression modification</p> Signup and view all the answers

    Which statement best describes the relationship between energy production rates and the quantity of ATP sources?

    <p>Energy production rates are inversely proportional to the quantity of ATP sources.</p> Signup and view all the answers

    At what running speed is the primary energy source composed mainly of ATP and creatine phosphate?

    <p>Up to 25 miles per hour</p> Signup and view all the answers

    What process is primarily catalyzed by creatine kinase during ATP energy demand?

    <p>Transfer of high-energy phosphate to ADP</p> Signup and view all the answers

    Which statement about anabolic pathways is true?

    <p>They synthesize complex compounds from simpler substances.</p> Signup and view all the answers

    What is a primary characteristic of the products yielded by catabolic pathways?

    <p>They are more oxidized than the starting materials.</p> Signup and view all the answers

    What role does NADPH play in metabolic pathways?

    <p>It is used as a reducing agent in anabolic reactions.</p> Signup and view all the answers

    During catabolic pathways, how is most ATP produced?

    <p>By oxidative phosphorylation after oxidation of NADH.</p> Signup and view all the answers

    What distinguishes anabolic pathways from catabolic pathways?

    <p>Anabolic pathways primarily involve reduction.</p> Signup and view all the answers

    Which statement accurately characterizes the energy dynamics of anabolic pathways?

    <p>They consume energy and often involve heat release.</p> Signup and view all the answers

    In the context of metabolism, what is the primary focus of catabolic pathways?

    <p>The creation of energy-rich intermediates.</p> Signup and view all the answers

    What distinguishes catabolic pathways from anabolic pathways?

    <p>Catabolic pathways generally involve oxidation and produce energy.</p> Signup and view all the answers

    Which of the following accurately describes the relationship between anabolic and catabolic pathways?

    <p>They are distinct pathways connecting similar compounds.</p> Signup and view all the answers

    Which of the following statements about anabolic processes is correct?

    <p>Anabolic pathways synthesize complex molecules from simpler ones.</p> Signup and view all the answers

    What is a common characteristic of enzymes in living organisms?

    <p>They speed up biological reactions and form specific products.</p> Signup and view all the answers

    In the context of metabolism, what is primarily produced from catabolic pathways?

    <p>Carbon dioxide and water as waste products.</p> Signup and view all the answers

    Which statement accurately reflects the relationship between catabolism and energy production?

    <p>Catabolism typically produces energy through oxidation reactions.</p> Signup and view all the answers

    What is a primary feature of metabolic pathways in living organisms?

    <p>They consist of enzyme-catalyzed reactions that are regulated.</p> Signup and view all the answers

    Which biomolecules yield the least energy during catabolic pathways?

    <p>Purines and pyrimidines.</p> Signup and view all the answers

    What is the primary purpose of metabolism in living cells?

    <p>To regulate and convert energy through biochemical reactions.</p> Signup and view all the answers

    What is the primary function of NADPH in metabolic reactions?

    <p>To provide reducing power for anabolic pathways</p> Signup and view all the answers

    What is the outcome of the reduction of NAD+ to NADH?

    <p>Release of protons into the solvent</p> Signup and view all the answers

    How does the structure of NADP+ differ from NAD+?

    <p>NADP+ contains a phosphate on the number two carbon of the lower ribose</p> Signup and view all the answers

    Which statement reflects the role of NADH in the electron transport system?

    <p>NADH donates high-energy electrons that drive ATP synthesis</p> Signup and view all the answers

    What is the expected result when NADH is oxidized in aerobic cells?

    <p>Conversion of ADP and inorganic phosphate into ATP</p> Signup and view all the answers

    Why do enzymes typically not recognize both NAD+ and NADP+?

    <p>The extra phosphate group in NADP+ alters binding properties</p> Signup and view all the answers

    What process produces the proton gradient necessary for ATP synthesis during oxidative phosphorylation?

    <p>High-energy electrons passing through the electron transport chain</p> Signup and view all the answers

    What is the primary energy source for the brain's metabolism?

    <p>Blood glucose</p> Signup and view all the answers

    In what manner does NAD+ primarily function during catabolic reactions?

    <p>As an oxidant accepting electrons from substrates</p> Signup and view all the answers

    Which mechanism is NOT involved in the regulation of metabolic activity?

    <p>Feedback inhibition via DNA replication</p> Signup and view all the answers

    Which of the following represents the correct relationship between energy sources and their usage during different running distances?

    <p>ATP and creatine phosphate are utilized more in short sprints.</p> Signup and view all the answers

    What role does creatine kinase play in energy metabolism?

    <p>Transfer of high energy phosphate from phosphocreatine to ADP</p> Signup and view all the answers

    Which energy source provides the most total ATP equivalents?

    <p>Stored fats</p> Signup and view all the answers

    How are metabolic activities localized within a cell?

    <p>By cellular compartmentalization</p> Signup and view all the answers

    What is one consequence of organ specialization in metabolism?

    <p>It enables the expression of specific metabolic enzymes in certain tissues.</p> Signup and view all the answers

    What happens to phosphocreatine during high energy demand?

    <p>It transfers high energy phosphate to ADP.</p> Signup and view all the answers

    What is the primary consequence of the hydrolysis of phosphoanhydride bonds in ATP?

    <p>It releases energy that can be used for other biochemical reactions.</p> Signup and view all the answers

    Which bond type in ATP is specifically responsible for the high energy release upon hydrolysis?

    <p>Phosphoanhydride bonds</p> Signup and view all the answers

    When glucose is phosphorylated using ATP, what is the overall change in ΔG for the reaction?

    <p>Positive ΔG, coupled with a favorable reaction to produce a negative ΔG</p> Signup and view all the answers

    Why is the inner α phosphate of ATP considered to release less energy upon hydrolysis?

    <p>It is linked to a carbon atom by a phosphoester bond.</p> Signup and view all the answers

    In the coupled reaction of ATP hydrolysis and glucose phosphorylation, which statement is accurate about the ΔG values involved?

    <p>The overall ΔG of the coupled reaction must be negative for it to occur.</p> Signup and view all the answers

    Hexokinase is essential in glycolysis. What specific role does it serve?

    <p>It catalyzes the transfer of a phosphate to glucose.</p> Signup and view all the answers

    What is the energy output of ATP hydrolysis generally compared to glucose phosphorylation?

    <p>Sufficient to drive glucose phosphorylation forward due to its negative ΔG.</p> Signup and view all the answers

    How does the process of ATP synthesis relate to catabolic reactions?

    <p>It is coupled to energy output from catabolic pathways.</p> Signup and view all the answers

    What is the approximate energy released per mole upon hydrolysis of the terminal phosphates in ATP?

    <p>7.3 kcal</p> Signup and view all the answers

    Which bond in ATP is primarily responsible for the energy released during hydrolysis?

    <p>Phosphoanhydride bond</p> Signup and view all the answers

    What type of reaction does hexokinase catalyze in glycolysis?

    <p>Phosphorylation reaction</p> Signup and view all the answers

    During which reaction is the hydrolysis of ATP coupled to drive an unfavorable reaction?

    <p>Phosphorylation of glucose</p> Signup and view all the answers

    What happens to the ΔG when a thermodynamically unfavorable reaction is coupled with a thermodynamically favorable one?

    <p>ΔG becomes negative</p> Signup and view all the answers

    What type of bond is formed between the inner α phosphate of ATP and a carbon atom in glucose-6-phosphate?

    <p>Phosphoester bond</p> Signup and view all the answers

    What distinguishes catabolic pathways from anabolic pathways in metabolism?

    <p>Catabolic pathways convert complex biomolecules into simpler products.</p> Signup and view all the answers

    What is the ΔG value of the reaction that combines glucose and inorganic phosphate to form glucose-6-phosphate?

    <p>13.9 kJ/mol</p> Signup and view all the answers

    Which statement about enzyme catalysis is incorrect?

    <p>Enzymes slow down the rate of biological reactions.</p> Signup and view all the answers

    What is required for the synthesis of ATP?

    <p>Energy input</p> Signup and view all the answers

    What is a primary function of catabolic pathways in living organisms?

    <p>To release energy from biomolecules.</p> Signup and view all the answers

    Which of the following best characterizes catabolic pathways for nitrogen-rich biomolecules?

    <p>They produce little or no energy.</p> Signup and view all the answers

    What role does the statement 'living things are composed of lifeless molecules' highlight in understanding metabolism?

    <p>Understanding metabolism requires a biochemical perspective.</p> Signup and view all the answers

    Which statement accurately describes the overall pattern of metabolism?

    <p>Metabolism encompasses all enzyme-catalyzed reactions in living cells.</p> Signup and view all the answers

    Why is it necessary to have an overall perspective on metabolic pathways?

    <p>To comprehend how pathways relate to each other in metabolism.</p> Signup and view all the answers

    Which pathway typically does NOT characterize catabolic processes?

    <p>Pathway synthesizing nucleic acids.</p> Signup and view all the answers

    What constitutes the primary function of anabolic pathways?

    <p>Synthesize complex biomolecules from simple precursors</p> Signup and view all the answers

    Which of the following accurately describes a characteristic of catabolic pathways?

    <p>They produce energy-rich intermediates like ATP and NADH</p> Signup and view all the answers

    What distinguishes NADPH in anabolic reactions?

    <p>It acts as a reducing agent</p> Signup and view all the answers

    During which of the following processes is molecular oxygen predominantly required?

    <p>Catabolic energy production</p> Signup and view all the answers

    Which statement about the energy dynamics of anabolic pathways is true?

    <p>They release heat as a byproduct, similar to catabolic pathways</p> Signup and view all the answers

    What happens to the products of catabolic pathways when reduced organic compounds are metabolized?

    <p>They yield products that are more oxidized</p> Signup and view all the answers

    Which of the following best describes the relationship between anabolic and catabolic pathways?

    <p>They are distinct, connecting the same compounds through different processes</p> Signup and view all the answers

    What role does the pentose phosphate pathway play in metabolism?

    <p>It produces NADPH used in anabolic reactions</p> Signup and view all the answers

    What is the primary energy source for the brain?

    <p>Blood glucose</p> Signup and view all the answers

    Which of the following mechanisms is NOT involved in the regulation of metabolic activity?

    <p>Signal transduction pathways</p> Signup and view all the answers

    What is the average maximum speed for a long-distance run compared to a sprint?

    <p>Approximately 13 miles/hour in a marathon</p> Signup and view all the answers

    What activates the transfer of high energy phosphate from phosphocreatine to ADP?

    <p>Creatine kinase</p> Signup and view all the answers

    Which metabolic substrate produces the least amount of total ATP equivalent?

    <p>ATP itself</p> Signup and view all the answers

    What is a key feature of muscle tissue metabolism?

    <p>Stores about 75% of human carbohydrate reserves as glycogen</p> Signup and view all the answers

    During what type of exercise is ATP and creatine phosphate primarily used?

    <p>Short sprints</p> Signup and view all the answers

    Why is cellular compartmentalization important in metabolism?

    <p>It allows specific metabolic activities to occur in designated areas.</p> Signup and view all the answers

    What is the primary role of NADH in aerobic cells?

    <p>To serve as a major electron donor in oxidative phosphorylation</p> Signup and view all the answers

    What differentiates NADP+ from NAD+ in terms of structure?

    <p>NADP+ contains an additional phosphate group</p> Signup and view all the answers

    During the reduction of NAD+ to NADH, what happens to the substrate being oxidized?

    <p>It loses two electrons and two protons</p> Signup and view all the answers

    In the context of metabolic pathways, what is the role of NADPH?

    <p>It acts as a reducing agent in anabolic reactions</p> Signup and view all the answers

    What is the main result of the oxidation of NADH during oxidative phosphorylation?

    <p>Formation of a proton gradient used for ATP synthesis</p> Signup and view all the answers

    Why don't enzymes that recognize NAD+ generally recognize NADP+?

    <p>The structural changes of NADP+ prevent binding to enzymes meant for NAD+</p> Signup and view all the answers

    What specific function does the nicotinamide ring of NAD+ serve in enzymatic reactions?

    <p>It accepts electrons and protons during reduction</p> Signup and view all the answers

    What is a consequence of the proton gradient established by the electron transport system in mitochondria?

    <p>Drives the synthesis of ATP via ATP synthase</p> Signup and view all the answers

    What is the primary distinction between catabolic and anabolic pathways in metabolism?

    <p>Catabolic pathways convert polymers into simpler products, whereas anabolic pathways synthesize polymers from simple building blocks.</p> Signup and view all the answers

    Which statement best describes the role of enzymes in metabolic reactions?

    <p>Enzymes decrease the activation energy of reactions, making them proceed faster.</p> Signup and view all the answers

    What is the primary storage form of fat in the human body?

    <p>Triglycerides</p> Signup and view all the answers

    How much caloric energy is typically stored as carbohydrates in the average human?

    <p>1500 kcal</p> Signup and view all the answers

    Which of the following best describes the overall purpose of metabolic pathways?

    <p>To efficiently transform energy and matter for cellular functions.</p> Signup and view all the answers

    Which metabolic pathway converts glucose into pyruvate?

    <p>Glycolysis</p> Signup and view all the answers

    What is typically produced during catabolic pathways that convert biomolecules into simpler products?

    <p>Energy primarily in the form of ATP.</p> Signup and view all the answers

    Which of the following statements about metabolic pathways is false?

    <p>Metabolic pathways are entirely independent of one another.</p> Signup and view all the answers

    What must a person burn to lose 1 pound of body weight?

    <p>3500 kcal</p> Signup and view all the answers

    Which of the following best describes proteins in energy storage during starvation?

    <p>Proteins are primarily hydrolyzed to amino acids for energy.</p> Signup and view all the answers

    During which metabolic processes do living organisms primarily utilize oxidation?

    <p>Catabolic pathways to extract energy.</p> Signup and view all the answers

    What is the fate of acetylCoA in aerobic conditions?

    <p>It is oxidized in the TCA cycle.</p> Signup and view all the answers

    What is the primary function of catabolic pathways as part of metabolism?

    <p>To degrade large biomolecules into smaller units and release energy.</p> Signup and view all the answers

    What are the outputs of energy production in humans?

    <p>Water and urea</p> Signup and view all the answers

    Which of the following components is specifically related to catabolic pathways in terms of energy production?

    <p>Consumption of oxygen in the production of carbon dioxide.</p> Signup and view all the answers

    Which pathway does not involve carbohydrates directly?

    <p>Fatty acid oxidation</p> Signup and view all the answers

    What distinguishes the oxidation process in living organisms from combustion in terms of energy utilization?

    <p>Energy is trapped as chemical energy in ATP.</p> Signup and view all the answers

    Which of the following best describes the function of NADP+ in metabolic processes?

    <p>It functions as an electron acceptor in anabolic reactions.</p> Signup and view all the answers

    What is the significance of the sequential oxidation of carbon atoms in metabolic pathways?

    <p>It facilitates the stepwise release of energy stored in organic molecules.</p> Signup and view all the answers

    How much energy can a living organism approximately capture as ATP from the oxidation of glucose?

    <p>Around 30 percent of the energy is captured.</p> Signup and view all the answers

    In the context of metabolism, what role do anabolic pathways primarily play?

    <p>They use energy to synthesize larger biochemical structures.</p> Signup and view all the answers

    What primarily distinguishes NADH from NADPH in metabolic reactions?

    <p>NADH typically functions in catabolic pathways, while NADPH is used in anabolic pathways.</p> Signup and view all the answers

    What is the primary output of catabolic pathways in terms of energy?

    <p>They generate chemical energy that can be used by the organism.</p> Signup and view all the answers

    Which of the following statements about the transformation of NAD+ to NADH is accurate?

    <p>Two protons and two electrons are accepted by the nicotinamide ring of NAD+.</p> Signup and view all the answers

    What type of metabolic reaction is primarily responsible for the transformation of carbon dioxide into more reduced compounds?

    <p>Anabolic reactions.</p> Signup and view all the answers

    How does the structure of NADP+ differ from that of NAD+?

    <p>NADP+ has an additional phosphate group on the second carbon of its ribose.</p> Signup and view all the answers

    Which process is essential for capturing energy during glucose oxidation in living organisms?

    <p>Trapping energy as ATP and other high-energy intermediates.</p> Signup and view all the answers

    What role does NADH play in oxidative phosphorylation?

    <p>NADH acts as a high-energy electron donor for the electron transport system.</p> Signup and view all the answers

    During the oxidation of NADH, what is produced as a byproduct?

    <p>Water.</p> Signup and view all the answers

    What is the primary function of the proton gradient generated in oxidative phosphorylation?

    <p>To drive ATP synthesis via ATPase.</p> Signup and view all the answers

    Which statement about the electron transport system is correct?

    <p>The passage of high-energy electrons is coupled with the pumping of protons across the membrane.</p> Signup and view all the answers

    Why do enzymes that recognize NAD+ typically not recognize NADP+?

    <p>The extra phosphate in NADP+ alters its binding properties significantly.</p> Signup and view all the answers

    Which statement best describes the brain's energy metabolism?

    <p>The brain relies exclusively on blood glucose as its energy source.</p> Signup and view all the answers

    What mechanism is not involved in the regulation of metabolic activity?

    <p>Nutrient availability</p> Signup and view all the answers

    Which of the following statements about phosphocreatine is true?

    <p>It can donate high energy phosphate to ADP to create ATP.</p> Signup and view all the answers

    How does muscle tissue primarily store energy?

    <p>As glycogen.</p> Signup and view all the answers

    What primarily differentiates energy sources in sprinting versus marathon running?

    <p>Type of biochemical pathway used</p> Signup and view all the answers

    What is a significant characteristic of enzyme regulation through covalent modification?

    <p>It has a long-lasting effect on enzyme activity.</p> Signup and view all the answers

    Which metabolic source provides the largest total ATP equivalents?

    <p>Stored fatty acids</p> Signup and view all the answers

    Why is maximal running velocity faster in short sprints compared to marathons?

    <p>Shorter distances utilize primarily ATP and creatine phosphate.</p> Signup and view all the answers

    Study Notes

    Overview of Metabolism

    • Metabolism encompasses all enzyme-catalyzed reactions and pathways within living cells.
    • It is divided into catabolism (breakdown of complex molecules) and anabolism (synthesis of complex molecules).
    • Catabolism is degradative, usually involves oxidation, and often produces energy.
    • Anabolism is synthetic, often involves reduction, and requires significant energy input.

    Central Themes in Metabolism

    • Catabolic pathways generate energy-rich intermediates: ATP, NADH, NADPH.
    • ATP is produced during the breakdown of carbohydrates, lipids, and proteins.
    • NADH is used to generate ATP through oxidative phosphorylation.
    • NADPH is vital for anabolic pathways, serving as the primary reductant.
    • All biomolecules can be synthesized from a few simple building blocks.
    • Degradative and biosynthetic pathways involving the same compounds are distinct.

    Summary of Catabolic Pathways

    • Catabolic pathways utilize reduced organic compounds (lipids, carbohydrates, and amino acids) as starting materials.
    • They yield more oxidized products, including pyruvate, acetyl-CoA, and carbon dioxide.
    • Molecular oxygen acts as the oxidizing agent.
    • Catabolic pathways generate energy, releasing some as heat.
    • ATP production occurs through substrate-level phosphorylation and oxidative phosphorylation.
    • NADPH is also generated for use as a reducing agent in anabolic reactions.

    Summary of Anabolic Pathways

    • Anabolic pathways synthesize complex molecules (lipids, carbohydrates, and proteins) from simple building blocks.
    • They produce more reduced products.
    • NADPH serves as the primary reducing agent.
    • ATP provides energy for thermodynamically unfavorable reactions.
    • Heat is released during anabolic pathways, similar to catabolic pathways.

    ATP and Energy Storage

    • Catabolic pathways release energy by oxidizing reduced organic compounds.
    • Some of this energy is stored as ATP.
    • ATP's outer two phosphate residues are linked by phosphoanhydride bonds.
    • Catabolic energy is used to create these phosphoanhydride bonds.
    • Hydrolysis of these bonds releases energy to drive unfavorable reactions.

    Coupled Reactions

    • Thermodynamically unfavorable reactions can be coupled with favorable reactions.
    • Shared intermediates enable energy transfer.
    • An example is ATP-dependent glucose phosphorylation, where ATP hydrolysis drives glucose phosphorylation.

    NADP+ Structure and Function

    • NADP+ is a coenzyme involved in redox reactions.
    • It contains an extra phosphate group compared to NAD+.
    • NADPH is the primary reducing agent in anabolic pathways.

    Oxidation and Reduction

    • Metabolism involves oxidation (loss of electrons) in catabolic pathways and reduction (gain of electrons) in anabolic pathways.
    • Carbon oxidation state is crucial for understanding energy production and storage.

    Energy Production and Efficiency

    • Complete combustion of glucose releases 687 kcal/mol, measured in a bomb calorimeter.
    • Living organisms capture some of this energy as chemical energy in ATP.
    • Efficiency of ATP production is estimated at around 30%.

    Fuel Reserves in Humans

    • Humans store energy as carbohydrates (glycogen), fats (triacylglycerols), and proteins.
    • Glycogen stores are limited, lasting less than a day.
    • Fat reserves are substantial, lasting for months.
    • Proteins are not primarily stored but can be utilized during starvation.

    Daily Energy Input and Output

    • Average daily energy expenditure for humans is 1500-2500 kcal.
    • Exercise significantly increases energy consumption.
    • Energy input primarily comes from carbohydrates, fats, and proteins.
    • Output products include carbon dioxide, water, and urea.

    Major Catabolic Pathways

    • Carbohydrates are broken down via glycolysis, producing pyruvate which is then converted to acetyl-CoA.
    • Fats are hydrolyzed to fatty acids and glycerol, both contributing to energy production.
    • Proteins are first hydrolyzed to amino acids, which can be converted to pyruvate, acetyl-CoA, or TCA cycle intermediates.
    • Acetyl-CoA is oxidized to carbon dioxide in the TCA cycle, generating NADH.
    • NADH is used in oxidative phosphorylation to produce ATP.

    Metabolic Profiles of Major Organs

    • Adipose tissue stores fat as triacylglycerols.
    • The liver converts lactic acid to glucose, stores glycogen, interconverts fats, releases energy-rich metabolites, and regulates their blood levels.

    ATP Stores Chemical Energy

    • The outer two phosphates of ATP (γ and β) are linked by phosphoanhydride bonds.
    • The hydrolysis of these phosphoanhydride bonds releases energy.
    • Catabolic pathways release energy by oxidizing reduced organic compounds.
    • The energy released is used to synthesize ATP phosphoanhydride bonds.
    • The energy for thermodynamically unfavorable reactions comes from ATP hydrolysis.

    Phosphoanhydride and Phosphoester Bonds

    • Phosphoanhydride bond hydrolysis in ATP releases ~7.3 kcal/mol of energy.
    • The α phosphate is linked to a carbon atom by a phosphoester bond.
    • Phosphoester bond hydrolysis releases less energy and is not typically coupled to energy requiring reactions.

    ATP Hydrolysis and Synthesis

    • ATP hydrolysis releases energy.
    • ATP hydrolysis provides energy input for other reactions.
    • ATP synthesis requires energy input.
    • ATP synthesis is coupled to energy output from catabolic reactions.

    Coupled Reactions

    • A thermodynamically unfavorable reaction (positive ΔG) can be made to occur if coupled with a thermodynamically favorable reaction (negative ΔG).
    • Coupled reactions involve shared intermediates.

    Glucose Phosphorylation

    • The ATP-dependent phosphorylation of glucose is an example of a coupled reaction.
    • The reaction of glucose + Pi to form glucose-6-P is unfavorable (ΔG = 13.9 kJ/mol).
    • The hydrolysis of ATP to ADP is favorable (ΔG = -30.5 kJ/mol).
    • The combined reaction has a negative ΔG (-16.6 kJ/mol).

    Hexokinase

    • Hexokinase catalyzes the ATP-dependent phosphorylation of glucose to glucose-6-P.
    • This is the first reaction of glycolysis.
    • The phosphate group is transferred from ATP's phosphoanhydride bond to a lower energy phosphoester bond in glucose-6-phosphate.

    NADH and NADPH

    • NAD+ is reduced to NADH during catabolic oxidation reactions.
    • NADH is a form of stored chemical energy.
    • Aerobic cells oxidize NADH, providing energy for ATP synthesis.
    • NADPH is a stored form of reducing power.
    • NADPH drives reductive biosynthesis reactions in anabolic pathways.

    Nicotinamide Adenine Dinucleotide

    • NAD+ functions as an acceptor of hydrogen and electrons in oxidation reactions.
    • NADP+ is the phosphorylated form of NAD+.
    • NADP+ serves as a donor of protons and electrons in reduction reactions.

    NAD+ Reduction

    • The nicotinamide ring of NAD+/NADP+ is the site of enzymatic activity.
    • It can exist in a reduced or oxidized state.
    • When NAD+ acts as an oxidant, it gains two electrons and a proton.
    • The substrate being oxidized loses two electrons and two protons.

    NADH in Oxidative Phosphorylation

    • NADH is the major electron donor in the electron transport system.
    • High energy electrons from NADH pass through the electron transport system.
    • Electrons react with oxygen and protons to produce water.
    • Proton translocation from the mitochondrial matrix to the intermembrane space is coupled to electron transport.
    • The proton gradient drives ATP synthesis by ATPase (hydrogen ion pump).

    Comparing NAD+ and NADP+

    • NADP+ has an extra phosphate on the number two carbon of the lower ribose ring.
    • The extra phosphate alters binding properties.
    • Enzymes that recognize one cofactor generally don't recognize the other.
    • NAD+ is usually an oxidant for catabolic reactions.
    • NADPH generally functions as a reductant for anabolic reactions.

    Oxidation and Reduction

    • Metabolism is composed of catabolism (oxidation of reduced compounds) and anabolism (reduction of oxidized compounds).

    Oxidation Levels of Carbon

    • Catabolism involves the stepwise oxidation of highly hydrogenated compounds to carbon dioxide.
    • Anabolism involves the sequential reduction of oxidized compounds like carbon dioxide to more reduced compounds.
    • This concept forms the basis of metabolic pathways and energy transfer.

    Glucose Combustion

    • Complete combustion of one mole of glucose releases ~687 kcal (2870 kJ) of energy as heat.
    • This is the maximum energy obtainable from glucose and oxygen.

    Glucose Oxidation in a Bomb Calorimeter

    • A bomb calorimeter measures the energy released as heat by oxidizing glucose to carbon dioxide.

    Glucose Oxidation in Living Organisms

    • The energy released from glucose oxidation in living organisms is the same as in a calorimeter.
    • A significant portion of the energy is captured as chemical energy (ATP).
    • Organisms can trap about 30% of energy as ATP.

    Fuel Reserves in Humans

    • Humans have energy reserves in addition to daily food intake.
    • Total reserves are ~1500 kcal carbohydrate (glycogen, less than one day), ~135,000 kcal fat (triglycerols, enough for months), and ~25,000 kcal protein (enough for days).
    • Major carbohydrate reserves are in liver and muscle glycogen.
    • Lipid reserves are mainly in adipose tissue.
    • Proteins are not stored but can be scavenged during starvation.

    Daily Energy Input and Output

    • Average human uses ~1500-2500 kcal/day.
    • Exercise increases energy expenditure.
    • Burning 3500 kcal results in 1 lb weight loss.
    • Major energy input sources: carbohydrate, fat, protein, and oxygen.
    • Major energy output products: carbon dioxide, water, and urea.

    Major Catabolic Pathways

    • Carbohydrates are funneled into glycolysis, converting glucose to pyruvate.
    • Under aerobic conditions, pyruvate is converted to acetylCoA.
    • Fats are hydrolyzed to fatty acids and glycerol.
    • Glycerol enters glycolysis.
    • Fatty acids are oxidized to acetylCoA.
    • Proteins are hydrolyzed to amino acids.
    • Amino acids are converted to pyruvate, acetylCoA, or TCA cycle intermediates.
    • Most catabolic pathways converge on acetylCoA.
    • AcetylCoA is oxidized to carbon dioxide in the TCA cycle.
    • NADH from the TCA cycle donates electrons to oxidative phosphorylation.
    • Oxidative phosphorylation uses electron energy to generate a proton gradient for ATP synthesis.

    Metabolic Profiles of Major Organs

    • Adipose tissue stores fat as triacylglycerols.
    • The liver converts lactic acid to glucose, stores glycogen, interconverts fats, releases metabolites into the blood, and regulates blood levels of intermediates.
    • The brain uses glucose for metabolism and nerve transmission.
    • The brain is entirely dependent on blood glucose.
    • Muscle uses fats and carbohydrates for energy.
    • Muscles contain 75% of human carbohydrate reserves as glycogen.

    Regulation of Metabolic Activity

    • Metabolic activity is regulated by multiple mechanisms.
    • Allosteric regulation: metabolites activate or inhibit enzyme activity.
    • Covalent modification of proteins directly regulates enzyme activity.
    • Gene expression regulates enzyme levels based on cellular needs.
    • Cellular compartmentalization allows specific metabolic activities in specific cell regions.
    • Organ specialization allows for tissue-specific metabolic activity.

    Maximum Running Velocity

    • ATP availability limits running velocity.
    • ATP itself provides ~223 mmol ATP equivalents.
    • Stored fatty acids provide ~4,000,000 mmol ATP equivalents.
    • Utilization rates are inversely proportional to quantity.
    • Short sprints (~25 miles/hour) utilize ATP and creatine phosphate.
    • Marathons (~13 miles/hour) utilize aerobic glucose and fatty acid metabolism.

    Creatine Kinase

    • Phosphocreatine serves as a backup high-energy phosphate storage.
    • Phosphocreatine transfers high-energy phosphate to ADP, extending ATP availability.
    • Creatine kinase catalyzes the phosphate transfer between phosphocreatine and ATP.

    Introduction to Metabolism

    • Metabolism is the collection of chemical processes that occur within living organisms.
    • Metabolism is divided into two categories—catabolism and anabolism.
    • Catabolism breaks down complex biomolecules into simpler molecules.
    • Anabolism builds complex molecules from simpler components.

    Energy Storage and Transfer

    • ATP is a central energy currency molecule in cells.
    • Phosphoanhydride bonds in ATP store high energy.
    • Hydrolysis of these bonds releases energy for cellular processes.
    • Coupled reactions link thermodynamically unfavorable reactions with favorable ones.
    • Glucose phosphorylation is an example of a coupled reaction.
    • NADH and NADPH are electron carriers involved in metabolism.
    • NADH is used for catabolic reactions, delivering electrons to oxidative phosphorylation.
    • NADPH is used for anabolic reactions, providing reducing power for biosynthesis.

    Energy Reserves in Humans

    • Humans store energy in various forms: carbohydrates (glycogen), fats (triglycerides), and proteins.
    • Carbohydrate reserves are primarily glycogen in liver and muscle.
    • Fat reserves are primarily triglycerides in adipose tissue.
    • Proteins are not stored, but working proteins like muscle can be used during starvation.

    Daily Energy Input and Output

    • The average human uses 1500-2500 kcal per day, depending on activity level.
    • Humans obtain energy from carbohydrates, fats, and proteins, along with oxygen.
    • Major output products are carbon dioxide, water, and urea.

    Major Catabolic Pathways

    • Carbohydrates are broken down in glycolysis, producing pyruvate.
    • Fats are hydrolyzed to fatty acids and glycerol, which enter glycolysis and are further broken down to acetyl-CoA.
    • Proteins are hydrolyzed to amino acids, which can be converted to pyruvate, acetyl-CoA, or TCA cycle intermediates.
    • Acetyl-CoA is a central molecule in catabolism, being oxidized in the TCA cycle.
    • The TCA cycle produces NADH, which is used in oxidative phosphorylation to generate ATP.

    Metabolic Profiles of Major Organs

    • Adipose tissue stores fat in the form of triglycerides.
    • Liver converts lactic acid to glucose, stores glycogen, regulates blood sugar levels, and processes fat.
    • Brain uses glucose for energy and nerve transmission, relying on blood glucose.
    • Muscle utilizes fats and carbohydrates for work, storing glycogen.

    Regulation of Metabolic Activity

    • Allosteric regulation involves metabolites directly activating or inhibiting enzyme activity.
    • Covalent modification of enzymes can regulate their activity.
    • Gene expression controls enzyme levels based on cell needs.
    • Cellular compartmentalization localizes metabolic activities to specific cellular regions.
    • Organ specialization enables specific tissues to carry out unique metabolic functions.

    ATP Production and Energy Utilization

    • ATP, phosphocreatine, and other energy storage molecules vary in their availability and utilization rates.
    • Creatine kinase catalyzes the transfer of high-energy phosphate from phosphocreatine to ADP.

    Central Themes in Metabolism

    • Anabolic pathways involve the synthesis of molecules, often through reduction and require significant amounts of energy.
    • Catabolic pathways break down substances, generating energy-rich compounds like ATP, NADH, and NADPH.
    • The breakdown of reduced organic compounds, including lipids, carbohydrates, and proteins, produces ATP.
    • NADH is produced during the oxidative catabolism of reduced organic compounds and used to generate ATP through oxidative phosphorylation.
    • NADPH is generated by the pentose phosphate pathway and serves as a reducing agent in anabolic pathways.
    • All biomolecules can be synthesized from a small set of building blocks.
    • Degradative and biosynthetic pathways that involve the same compounds are distinct.

    Catabolic Pathways

    • Catabolic pathways utilize reduced organic compounds (lipids, carbohydrates, and amino acids) as starting materials.
    • They produce more oxidized products like pyruvate, acetylCoA, and carbon dioxide.
    • Molecular oxygen is used as an oxidizing agent in catabolic pathways.
    • The primary focus of catabolism is energy production.
    • Much of the energy released during catabolic reactions is dissipated as heat.
    • Some energy is directly harnessed to synthesize ATP through substrate level phosphorylation.
    • Some energy is used to synthesize NADH, further generating ATP through oxidative phosphorylation.
    • Some energy is used to synthesize NADPH, a reducing agent used in anabolic reactions.

    Anabolic Pathways

    • Anabolic pathways synthesize complex molecules (lipids, carbohydrates, and proteins) from simpler starting materials.
    • Their products are more reduced than the starting materials.
    • Anabolic processes use NADPH as the reducing agent.
    • Most anabolic pathways utilize ATP to drive thermodynamically unfavorable reactions.
    • They lead to the net release of energy as heat, similar to catabolic pathways.

    ATP: Storing Chemical Energy

    • Catabolic pathways release energy by oxidizing reduced organic compounds.
    • Some of this released energy is stored as ATP.
    • The outer two phosphate groups in ATP are linked by phosphoanhydride bonds.
    • The energy from catabolic pathways is used to create these phosphoanhydride bonds within ATP.
    • Hydrolysis of these phosphoanhydride bonds provides energy for thermodynamically unfavorable reactions.

    Phosphoanhydride and Phosphoester Bonds in ATP

    • The two terminal phosphate groups (γ and β) of ATP release high amounts of energy upon hydrolysis.
    • They are connected via phosphoanhydride bonds, releasing approximately 7.3 kcal/mol during hydrolysis.
    • The inner α phosphate, linked to a carbon atom by a phosphoester bond, releases significantly less energy upon hydrolysis and is not typically involved in energy-requiring reactions.

    Hydrolysis and Synthesis of ATP

    • Hydrolysis of ATP releases energy and serves as an energy source for other biochemical reactions.
    • ATP synthesis requires energy input and is coupled to energy output from catabolic reactions.

    Coupled Reactions

    • Thermodynamically unfavorable reactions (positive ΔG) can occur when coupled with favorable reactions (negative ΔG).
    • These reactions share intermediates.

    Glucose Phosphorylation as a Coupled Reaction

    • ATP-dependent phosphorylation of glucose illustrates the coupling of unfavorable and favorable reactions.
    • The reaction of glucose and Pi to form glucose-6-P is unfavorable (positive ΔG of 13.9 kJ/mol).
    • ATP hydrolysis to ADP is favorable (negative ΔG of -30.5 kJ/mol).
    • Combining these reactions, where ATP transfers its γ phosphate to glucose, results in a favorable overall reaction (negative ΔG of -16.6 kJ/mol).

    Hexokinase Chemistry

    • ATP-dependent phosphorylation of glucose to form glucose-6-P is the initial reaction in glycolysis.
    • It is catalyzed by the enzyme hexokinase.
    • The phosphate group is transferred from the phosphoanhydride bond in ATP to a lower energy phosphoester bond in glucose-6-phosphate.

    Structure of NADP+

    • NADP+ contains an extra phosphate residue on the C-2' of the lower ribose ring.

    Oxidation and Reduction

    • Metabolism encompasses catabolism, where reduced compounds are oxidized to produce chemical energy, and anabolism, where oxidized compounds are reduced to build biochemical intermediates and macromolecules.

    Oxidation Levels of Carbon

    • Energy production in catabolic pathways involves the stepwise oxidation of highly hydrogenated compounds to carbon dioxide.
    • The process starts with the most reduced state (alkanes) and progresses to the most oxidized form (carbon dioxide).
    • Anabolic pathways often use energy to reduce oxidized compounds like carbon dioxide to more reduced forms (alkanes).

    Combustion of Glucose

    • Complete oxidation of one mole of glucose to carbon dioxide releases approximately 687 kcal (2870 kJ) of energy as heat.
    • This represents the maximum energy obtainable from glucose and oxygen.

    Oxidation of Glucose in a Bomb Calorimeter

    • The amount of energy released as heat by oxidizing glucose to carbon dioxide can be measured in a bomb calorimeter.

    Oxidation of Glucose in a Living Organism

    • The energy released during glucose oxidation in a living organism is equivalent to that measured in a bomb calorimeter.
    • However, a significant portion of this energy is captured as chemical energy, reducing the amount of heat produced.
    • Organisms effectively trap energy from oxidation as chemical energy in ATP (estimated at about 30% efficiency).

    Fuel Reserves in Humans

    • Humans have energy reserves in addition to daily food intake.
    • The average human has approximately:
      • 1500 kcal of carbohydrate as glycogen (less than a day's energy supply)
      • 135,000 kcal as fat (enough for a month or two)
      • 25,000 kcal as protein (enough for 15 or 20 days)
    • The primary carbohydrate reserves are stored as glycogen in the liver and muscle.
    • Lipids are mainly stored as triglycerides in adipose tissue.
    • Proteins are not stored for energy but can be broken down during starvation.

    Daily Input and Output of Energy

    • The average human uses 1500-2500 kcal per day, depending on exercise levels.
    • Intense activities, like marathons (26.2 miles) and ultra-marathons (24 hours), can expend significantly more energy (3500 kcal for a marathon, 24,000 kcal for an ultra-marathon).
    • Losing one pound of body weight requires burning approximately 3500 kcal.
    • The main energy input sources for humans are carbohydrates, fats, proteins, and oxygen.
    • The primary output products of energy production include carbon dioxide, water, and urea (urea helps eliminate excess nitrogen).

    The Major Catabolic Pathways

    • Carbohydrates are processed through glycolysis, converting glucose to pyruvate.
    • Under aerobic conditions, pyruvate is further converted to acetylCoA.
    • Stored fats are broken down into fatty acids and glycerol. Glycerol enters glycolysis, while fatty acids are oxidized to acetylCoA.
    • Proteins are initially hydrolyzed into amino acids, which can be converted into pyruvate, acetylCoA, or intermediates of the TCA cycle.
    • Most catabolic pathways converge on acetylCoA, which is further oxidized to carbon dioxide in the TCA cycle.
    • The primary energy-rich product of the TCA cycle is NADH, which donates electrons to the oxidative phosphorylation system.
    • The energy from these electrons drives the creation of a proton gradient, ultimately leading to ATP formation.

    Metabolic Profiles of Major Organs I

    • Adipose tissue functions as a storage site for fat in the form of triacylglycerols.
    • The liver converts lactic acid to glucose, stores carbohydrate as glycogen, interconverts fat forms, releases energy-rich metabolites into the bloodstream, and regulates the levels of these intermediates.

    Metabolic Profiles of Major Organs II

    • The brain relies heavily on glucose for metabolism and nerve transmission, and is entirely dependent on blood glucose for energy.
    • Muscle tissue uses fats and carbohydrates to produce work. Approximately 75% of human carbohydrate reserves are stored in muscle as glycogen.

    Regulation of Metabolic Activity

    • Various mechanisms regulate metabolic activity:
      • Allosteric regulation: Metabolites directly activate or inhibit enzyme activity.
      • Covalent modification: Enzyme activity is regulated through covalent modification of proteins.
      • Gene expression: Changes in enzyme levels are influenced by mechanisms that regulate gene expression, adapting to cellular metabolic needs.
      • Cellular compartmentalization: Metabolic activities are confined to specific areas of the cell.
      • Organ specialization: Metabolic activities are expressed differently in various tissues.

    Maximum Running Velocity at Different Distances

    • The total ATP equivalents available from various sources range from 223 mmol (ATP itself) to 4,000,000 mmol (stored fatty acids).
    • The rates at which these equivalents can be utilized for energy production are inversely proportional to their quantity.
    • This is reflected in world records for running different distances:
      • Short sprints (relying mostly on ATP and creatine phosphate) are faster (around 25 miles/hour).
      • Marathons (primarily fueled by aerobic metabolism of glucose and fatty acids) have slower paces (around 13 miles/hour).

    Creatine Kinase

    • Phosphocreatine serves as a backup storage form of high-energy phosphate.
    • When there is an immediate need for ATP energy, the high-energy phosphate from phosphocreatine can be transferred to ADP, extending the availability of ATP energy.
    • The transfer of high-energy phosphate between phosphocreatine and ATP is catalyzed by creatine kinase.

    Naked Greek Guys Still Running

    • This section appears to be setting up a hypothetical scenario involving Greek athletes running and their energy expenditure.
    • It poses a question about the number of kcal expended within a 30-minute period.

    Overview of Metabolism

    • General Features of Metabolism: Metabolism refers to all reactions catalyzed by enzymes that occur within living cells. Metabolism is divided into catabolism, which breaks down complex compounds, and anabolism, which builds complex compounds.

    Catabolism

    • Degradative Pathways: Catabolic pathways break down complex molecules like carbohydrates, proteins, and lipids into simpler products including carbon dioxide, water, and urea.
    • Oxidative Reactions: Catabolism involves oxidation, which releases energy.
    • Energy Production: Catabolism in biomolecules with high carbon content (like carbohydrates, proteins, and lipids) generates energy.
    • Nitrogen-Rich Biomolecules: Catabolism of nitrogen-rich molecules (like purines and pyrimidines) does not significantly produce energy.

    Anabolism

    • Synthetic Pathways: Anabolic pathways use simpler building blocks to synthesize complex biomolecules or polymers.
    • Reductive Reactions: Anabolism often involves reduction processes.
    • Energy Consumption: Anabolic pathways require energy input.

    Central Themes in Metabolism

    • Energy-Rich Intermediates: Catabolic pathways aim to synthesize energy-rich intermediates like ATP, NADH, and NADPH.
    • ATP Generation: Catabolism of reduced organic compounds generates ATP.
    • NADH & Oxidative Phosphorylation: NADH is produced during oxidative catabolism and utilized for ATP production through oxidative phosphorylation.
    • NADPH & Anabolic Pathways: NADPH is generated by the pentose phosphate pathway, and it is the primary reductant in anabolic reactions.
    • Simple Building Blocks: All biomolecules can be synthesized from a few fundamental building blocks.
    • Distinct Pathways: Catabolic and anabolic pathways that involve the same compounds are always distinct.

    ATP Stores Chemical Energy

    • Catabolism & Energy Release: Catabolic reactions break down reduced organic compounds and release energy.
    • ATP Storage: Some of the energy released during catabolism is stored in ATP.
    • Phosphoanhydride Bonds: The outer two phosphate groups in ATP are linked by phosphoanhydride bonds, which store energy.
    • ATP Synthesis: Energy from catabolic pathways is used to synthesize ATP by forming phosphoanhydride bonds.
    • ATP Hydrolysis: Hydrolysis of phosphoanhydride bonds releases energy and drives thermodynamically unfavorable reactions.

    NADH & NADPH

    • NAD+ Oxidation: NAD+ acts as an oxidant by accepting electrons and hydrogen during catabolic reactions.
    • NADH Reductant: NADH stores chemical energy and can be oxidized in aerobic cells to generate ATP.
    • NADPH Reductant: NADPH stores reducing power and drives reductive biosynthetic reactions in anabolic pathways.

    Coupled Reactions

    • Unfavorable Reactions: A thermodynamically unfavorable reaction (positive ΔG) can occur if coupled to a favorable reaction (negative ΔG).
    • Shared Intermediates: Coupled reactions share intermediate molecules.

    Glucose Phosphorylation: A Coupled Reaction Example

    • Unfavorable Reaction: The phosphorylation of glucose to form glucose-6-P is unfavorable (positive ΔG).
    • ATP Hydrolysis: ATP hydrolysis is favorable (negative ΔG).
    • Coupling: Coupling these reactions allows the unfavorable glucose phosphorylation to proceed with a negative ΔG overall.

    Metabolic Profiles of Major Organs

    • Liver: The liver is a central metabolic hub responsible for maintaining glucose homeostasis and synthesizing and detoxifying substances.
    • Brain: The brain relies heavily on glucose for metabolism and nerve transmission, and is totally dependent on blood glucose.
    • Muscle: Muscles utilize both carbohydrates and fats for energy production.

    Regulation of Metabolic Activity

    • Allosteric Regulation: Metabolites can directly activate or inhibit enzyme activity.
    • Covalent Modification: Enzyme activity is also regulated by covalent modification, such as phosphorylation.
    • Gene Expression: Changes in enzyme levels are regulated by gene expression.
    • Cellular Compartmentalization: Specific metabolic activities are localized to different regions within cells.
    • Organ Specialization: Different organs have distinct metabolic activity based on their function.

    Creatine Kinase

    • Phosphocreatine: Phosphocreatine serves as a backup high-energy phosphate reserve.
    • Energy Transfer: During high energy needs, creatine kinase catalyzes the transfer of high energy phosphate from phosphocreatine to ADP, effectively extending ATP availability.

    Metabolism Overview

    • Metabolism encompasses all enzyme-catalyzed reactions and pathways within living cells.
    • Two main categories encompass metabolism: catabolism and anabolism.
    • Catabolism refers to pathways converting complex biomolecules into simpler products, involving degradation, oxidation, and often energy production.
    • Anabolism refers to pathways building complex biomolecules from simpler building blocks, involving synthesis, reduction, and significant energy consumption.

    Central Themes in Metabolism

    • Catabolic pathways synthesize energy-rich intermediates like ATP, NADH, and NADPH.
    • ATP is generated during the catabolism of reduced organic compounds (lipids, carbohydrates, proteins).
    • NADH is generated during the oxidative catabolism of reduced organic compounds and used to produce ATP through oxidative phosphorylation.
    • NADPH is generated by the pentose phosphate pathway and utilized as the primary reductant in anabolic pathways.
    • All biomolecules are synthesized from a few basic building blocks.
    • Degradative oxidative pathways and biosynthetic anabolic pathways connecting the same compounds are always distinct.

    Catabolic Pathways Summary

    • Catabolic pathways utilize reduced organic compounds (lipids, carbohydrates, and amino acids) as starting materials.
    • They yield products like pyruvate, acetyl-CoA, and carbon dioxide, which are more oxidized than the starting materials.
    • They employ molecular oxygen as the oxidizing agent.
    • A central focus of catabolism is net energy production.
    • Energy released during catabolic reactions is mostly released as heat.
    • Some energy is used directly through substrate-level phosphorylation to produce ATP.
    • Some energy is used to synthesize NADH, which is later converted to ATP through oxidative phosphorylation.
    • Some energy is used to synthesize NADPH, which acts as a reducing agent in anabolic reactions.

    Anabolic Pathways Summary

    • Anabolic pathways synthesize complex end products (lipids, carbohydrates, and proteins) from simpler starting materials.
    • They yield products more reduced than the starting materials.
    • They use NADPH as the reducing agent.
    • Most anabolic pathways utilize ATP to drive unfavorable reactions.
    • They result in the net release of energy as heat, similar to catabolic pathways.

    ATP and Chemical Energy

    • Catabolic pathways release energy by oxidizing reduced organic compounds.
    • Some of this energy is stored as ATP.
    • The outer two phosphate residues of ATP are linked by phosphoanhydride bonds.
    • Energy from catabolic pathways is used to synthesize these phosphoanhydride bonds in ATP.
    • The hydrolysis of these bonds provides energy to power thermodynamically unfavorable reactions.

    Phosphoanhydride and Phosphoester Bonds in ATP

    • The two terminal phosphates (γ and β phosphates) of ATP release significant energy upon hydrolysis.
    • These phosphates are linked by phosphoanhydride bonds, releasing approximately 7.3 kcal per mole upon hydrolysis.
    • The α phosphate, linked to a carbon atom by a phosphoester bond, releases much less energy upon hydrolysis and is not generally coupled to energy-requiring reactions.

    Hydrolysis and Synthesis of ATP

    • ATP hydrolysis releases energy and serves as an energy source for other biochemical reactions.
    • ATP synthesis requires energy input and is coupled to energy output from catabolic reactions.

    Coupled Reactions

    • A thermodynamically unfavorable reaction (positive ΔG) can be made to occur by coupling it with a favorable reaction (negative ΔG).
    • Coupled reactions involve shared intermediates.

    Glucose Phosphorylation as a Coupled Reaction

    • ATP-dependent phosphorylation of glucose illustrates the coupling of unfavorable and favorable reactions.
    • Glucose plus Pi to form glucose-6-P is unfavorable with a positive ΔG of 13.9 kJ/mol.
    • ATP hydrolysis to ADP has a negative ΔG of -30.5 kJ/mol.
    • When combined, ATP transfers its γ phosphate to glucose, resulting in a negative ΔG of -16.6 kJ/mol for the overall reaction.

    Hexokinase Chemistry

    • The ATP-dependent phosphorylation of glucose to form glucose-6-P, catalyzed by hexokinase, is the first reaction of glycolysis.
    • The phosphate group transfers from the phosphoanhydride bond in ATP to a lower energy phosphoester bond in glucose-6-phosphate.

    NADH and NADPH

    • NAD+ is reduced to NADH during many oxidative reactions in catabolism.
    • NAD+ collects electrons released during catabolism.
    • NADH is a stored form of chemical energy.
    • It can be oxidized in aerobic cells, providing energy for ADP + Pi --> ATP.
    • NADPH is a stored form of reducing power used to drive reductive biosynthetic reactions in anabolic pathways.

    Nicotinamide Adenine Dinucleotide (NAD+)

    • NAD+ functions in oxidation reactions, accepting hydrogen and electrons.
    • NADP+ functions in its reduced form, donating protons and electrons in reduction reactions.

    Reduction of NAD+ to NADH plus H+

    • The nicotinamide ring of NAD+ (and NADP+) is involved in enzymatic activity and can exist in a reduced or oxidized state.
    • The riboses, phosphates, and adenine base are involved in binding to enzyme active sites.
    • When NAD+ acts as an oxidant, the nicotinamide ring gains two electrons and a proton, with another proton going into the solvent.
    • The substrate being oxidized loses two electrons and two protons.

    Role of NADH in Oxidative Phosphorylation

    • NADH is the major electron donor in the electron transport system of oxidative phosphorylation.
    • High-energy electrons from NADH pass through the electron transport system, ultimately reacting with oxygen and protons to produce water.
    • This passage of electrons is coupled to the translocation of protons from the mitochondrial matrix to the intermembrane space.
    • The proton gradient drives ATPase, a hydrogen ion pump, to synthesize ATP.

    Comparing NAD+ and NADP+

    • The structure of NADP+ is identical to NAD+, except for a phosphate on the 2-carbon of the lower ribose ring.
    • The extra phosphate alters the binding properties of these cofactors.
    • Enzymes that recognize one cofactor usually do not recognize the other.
    • NAD+ is typically an oxidant in catabolic reactions, while NADPH generally functions as a reductant in anabolic reactions.

    Metabolic Profiles of Major Organs

    • Organs have distinct metabolic profiles based on their functions and energy requirements.
    • The liver plays a central role in carbohydrate metabolism, storing glucose as glycogen and releasing it when needed.
    • It also synthesizes various molecules like fatty acids, proteins, and cholesterol.
    • Muscle tissue uses glucose for work, stores approximately 75% of human carbohydrate reserves as glycogen, and uses fats and carbohydrates to produce energy.
    • Fat tissue stores fats as triglycerides, mobilizing them as energy sources.
    • The brain relies heavily on glucose for metabolism and nerve transmission, completely dependent on blood glucose for energy.

    Regulation of Metabolic Activity

    • Metabolic activity is regulated through various mechanisms:
      • Allosteric regulation: metabolites directly activate or inhibit enzyme activity levels.
      • Covalent modification: enzyme activity is directly regulated by covalent modification of proteins.
      • Gene expression regulation: changes in enzyme levels occur based on cellular metabolic needs.
      • Cellular compartmentalization: specific metabolic activities are localized to particular cellular regions.
      • Organ specialization: metabolic activities are expressed in specific tissues.

    Maximum Running Velocity at Different Distances

    • The total ATP equivalents available from various sources vary from approximately 223 mmol from ATP itself to 4,000,000 mmol from stored fatty acids.
    • The rates at which these equivalents are utilized for energy production are almost inversely proportional to their quantity.
    • This is reflected in the world record running speeds for different distances, ranging from 25 mph for a short sprint (mostly ATP and creatine phosphate) to 13 mph for a marathon (primarily aerobic glucose and fatty acid metabolism).

    Creatine Kinase

    • Phosphocreatine serves as a backup storage form of high-energy phosphate.
    • When immediate ATP energy is needed, high-energy phosphate from phosphocreatine can be transferred to ADP, extending ATP availability.
    • This transfer is catalyzed by creatine kinase.

    Metabolism

    • Metabolism encompasses all enzyme-catalyzed reactions and pathways within living cells.
    • It can be divided into two components: Catabolism and Anabolism.

    Catabolism

    • Degradative pathways that break down complex biomolecules into simpler products like carbon dioxide, water, and urea.
    • Involve oxidation and often produce energy.
    • Carbohydrates, proteins, and lipids are primarily catabolized to release energy.
    • Catabolic pathways for nitrogen-rich biomolecules (purines and pyrimidines) produce little to no energy.

    Anabolism

    • Constructive metabolic pathways that synthesize complex biomolecules and polymers from simpler building blocks.
    • Often require energy.
    • NADPH, a stored form of reducing power, is essential for reductive biosynthesis in anabolic pathways.

    NAD+ and NADPH

    • NAD+ acts as an electron acceptor in catabolic oxidation reactions, transforming into its reduced form NADH.
    • NADH represents stored chemical energy and can be oxidized in aerobic cells to provide energy for ATP synthesis (ADP + Pi -->ATP).
    • NADPH is a reductant in anabolic reactions, providing electrons for biosynthesis.
    • The difference between NAD+ and NADP+ lies in a phosphate group on the lower ribose ring of NADP+, altering their binding properties and making them specific to different enzymes.

    Oxidation and Reduction in Metabolism

    • Catabolism involves the oxidation of reduced compounds, releasing energy.
    • Anabolism involves the reduction of oxidized compounds, requiring energy.

    Carbon Oxidation Levels

    • Energy production in catabolic pathways involves the stepwise oxidation of highly hydrogenated compounds to carbon dioxide.
    • Anabolic pathways often use energy to reduce oxidized compounds like carbon dioxide to more reduced forms.

    Energy Production from Glucose

    • Burning one mole of glucose to carbon dioxide releases 687 kcal (2870 kJ) of energy as heat.
    • In living organisms, a significant portion of this energy is captured as chemical energy in ATP, with about 30% efficiency.

    Fuel Reserves in Humans

    • Humans store energy in the form of carbohydrates (glycogen, less than a one-day supply), lipids (triglycerides, enough for a month or two), and proteins (not primarily stored, but can be scavenged during prolonged starvation).

    Daily Energy Input and Output

    • Average humans use 1500-2500 kcal per day, with higher energy expenditure during exercise.
    • Major energy sources: carbohydrates, fats, proteins, and oxygen.
    • Major output products: carbon dioxide, water, and urea.

    Major Catabolic Pathways

    • Carbohydrates are metabolized through glycolysis, producing pyruvate which is converted to acetylCoA under aerobic conditions.
    • Fats are broken down into fatty acids and glycerol. Glycerol enters glycolysis, while fatty acids are oxidized to acetylCoA.
    • Proteins are hydrolyzed to amino acids, which are converted into pyruvate, acetylCoA, or TCA cycle intermediates.
    • AcetylCoA is further oxidized in the TCA cycle to produce NADH, the primary energy-rich product.
    • NADH donates electrons to oxidative phosphorylation, generating a proton gradient that drives ATP synthesis.

    Metabolic Profiles of Major Organs

    • Adipose tissue stores fats as triglycerides.
    • Liver converts lactic acid to glucose, stores glycogen, interconverts fats, releases energy-rich metabolites, and regulates blood glucose levels.
    • Brain relies primarily on glucose for metabolism and nerve transmission.
    • Muscle utilizes fats and carbohydrates for energy production and work.

    Regulation of Metabolic Activity

    • Allosteric regulation by metabolites directly affects enzyme activity (activation or inhibition).
    • Covalent modification of proteins directly regulates enzyme activity.
    • Gene expression regulation controls enzyme levels based on cellular needs.
    • Cellular compartmentalization confines specific metabolic activities to specific areas within the cell.
    • Organ specialization allows specific tissues to perform specialized metabolic functions.

    Creatine Kinase and Phosphocreatine

    • Phosphocreatine serves as a high-energy phosphate reservoir, providing backup energy for ATP synthesis when needed.
    • Creatine kinase catalyzes the transfer of high-energy phosphate between phosphocreatine and ATP.

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    Lecture 13: Overview of Metabolism PDF

    Description

    This quiz covers the fundamental concepts of metabolism, including catabolic and anabolic pathways. Understand the roles of ATP, NADH, and NADPH in energy production and synthesis of biomolecules. Test your knowledge on how these pathways interact and are regulated in living cells.

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