Metabolism and Energy Use
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Questions and Answers

What is the primary function of the ATP-ADP cycle?

  • To synthesize proteins from amino acids
  • To convert glucose into pyruvate
  • To transport electrons through the cell
  • To provide energy for other reactions (correct)

    • Which metabolite is considered a common currency in redox reactions?

  • NADH (correct)
  • Coenzyme A
  • FADH2
  • ATP

    • What is the change in free energy (ΔG) when glucose is phosphorylated by ATP?

  • 0 kJ/mol
  • -30.5 kJ/mol
  • -16.7 kJ/mol (correct)
  • +13.8 kJ/mol

    • During which process are NAD+ and FAD reduced to NADH and FADH2?

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

    Which statement best describes intermediary metabolism?

    <p>It encompasses the metabolic conversion of food to energy and cellular components.</p> Signup and view all the answers

    Which statement accurately defines catabolic pathways?

    <p>They involve the degradation of molecules.</p> Signup and view all the answers

    What is the primary function of anabolic pathways?

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

    What best describes a converging metabolic pathway?

    <p>It is primarily catabolic in nature.</p> Signup and view all the answers

    How do catabolic pathways contribute to anabolic pathways?

    <p>By generating energy-rich molecules like ATP and NADH.</p> Signup and view all the answers

    Which of the following best characterizes the relationship between synthetic and degradative pathways?

    <p>They are distinct, allowing for better control of metabolism.</p> Signup and view all the answers

    What is metabolism primarily concerned with?

    <p>Generating and using energy within an organism</p> Signup and view all the answers

    Which molecule is described as the common currency in energy exchange?

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

    In what process is energy captured during metabolism?

    <p>Oxidation of food fuel</p> Signup and view all the answers

    What is the role of NADH in metabolism?

    <p>It is involved in generating and transferring energy</p> Signup and view all the answers

    Which of the following does NOT represent a use of energy in organisms?

    <p>Storage of genetic information</p> Signup and view all the answers

    What is an anabolic process?

    <p>Synthesizing complex molecules from simpler ones</p> Signup and view all the answers

    Which component is primarily involved in the transport of energy?

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

    What are inherited errors of metabolism most often linked to?

    <p>Impaired enzyme activity</p> Signup and view all the answers

    Which type of molecules are produced by anabolic pathways?

    <p>Metabolic intermediates</p> Signup and view all the answers

    What is a common characteristic of both anabolic and catabolic pathways?

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

    Which of the following molecules is considered energy-depleted?

    <p>H2O</p> Signup and view all the answers

    Which regulation mechanism affects enzyme activity in metabolic pathways?

    <p>Rate of enzyme synthesis/degradation</p> Signup and view all the answers

    What primarily distinguishes anabolic pathways from catabolic pathways?

    <p>Anabolic pathways build complex molecules.</p> Signup and view all the answers

    Which of the following describes a function of metabolic intermediates?

    <p>They link anabolic and catabolic processes.</p> Signup and view all the answers

    What happens to enzyme activity during phosphorylation?

    <p>It may enhance or reduce enzyme activity.</p> Signup and view all the answers

    What is one way that metabolic pathways are compartmentalized?

    <p>By separating enzymes in organelles.</p> Signup and view all the answers

    What role do allosteric activators play in metabolic pathways?

    <p>They enhance enzyme activity.</p> Signup and view all the answers

    What typically inhibits the activity of the first enzyme in a metabolic pathway?

    <p>The end product of the pathway.</p> Signup and view all the answers

    Which metabolic pathway synthesizes glucose from non-carbohydrate sources?

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

    What is a consequence of impaired enzyme activity in a metabolic pathway?

    <p>Accumulation of substrate A.</p> Signup and view all the answers

    Which of the following is involved in lipid metabolism?

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

    Which pathway is responsible for the degradation of glucose to pyruvate?

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

    In carbohydrate metabolism, what is the outcome of glycogenolysis?

    <p>Degradation of glycogen into glucose.</p> Signup and view all the answers

    What is the primary purpose of intermediary metabolism?

    <p>To facilitate the synthesis of different macromolecules.</p> Signup and view all the answers

    Which of the following processes refers to the synthesis of proteins from amino acids?

    <p>Protein synthesis.</p> Signup and view all the answers

    What does oxidative phosphorylation primarily generate?

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

    What is the main role of the urea cycle?

    <p>To convert ammonia to urea.</p> Signup and view all the answers

    During beta-oxidation, what are fatty acids converted into?

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

    Which type of amino acid can be converted to glucose?

    <p>Glucogenic amino acids.</p> Signup and view all the answers

    What is the main function of glycolysis?

    <p>To convert glucose into energy.</p> Signup and view all the answers

    What is the overall free energy change (ΔG) for the reaction in which glucose is phosphorylated by ATP?

    <p>-16.7 kJ/mol</p> Signup and view all the answers

    In the electron transport chain, which primary electron acceptors are regenerated from NADH and FADH2?

    <p>NAD+ and FAD</p> Signup and view all the answers

    What does the gross change in free energy (ΔG) represent in coupled reactions involving ATP?

    <p>The energy released that can drive other reactions.</p> Signup and view all the answers

    Which metabolic processes are contained within intermediary metabolism?

    <p>Conversion of food, energy storage, and waste disposal.</p> Signup and view all the answers

    What is the primary function of ATP hydrolysis in cellular reactions?

    <p>To drive energy-requiring reactions through the release of energy.</p> Signup and view all the answers

    What is the primary characteristic of catabolic pathways?

    <p>They release energy by breaking down complex molecules.</p> Signup and view all the answers

    Which statement accurately describes anabolic pathways?

    <p>They convert simple molecules into complex structures.</p> Signup and view all the answers

    What is an essential function of macromolecules generated via anabolic pathways?

    <p>They provide structure and support within cells.</p> Signup and view all the answers

    How do converging metabolic pathways generally function?

    <p>They generate intermediates for both anabolic and catabolic pathways.</p> Signup and view all the answers

    What is a key distinction between synthetic and degradative pathways?

    <p>Degradative pathways are designed for better control and regulation.</p> Signup and view all the answers

    What is the definition of metabolism?

    <p>The sum of chemical processes within an organism that are necessary to sustain life.</p> Signup and view all the answers

    Which processes utilize energy within an organism?

    <p>Active transport and mechanical work.</p> Signup and view all the answers

    What role does ATP play in metabolic processes?

    <p>It serves as the common currency for energy exchange.</p> Signup and view all the answers

    What is a primary goal of catabolic processes?

    <p>To generate ATP and NADH by breaking down substrates.</p> Signup and view all the answers

    Which type of metabolism is focused on building larger molecules?

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

    What is meant by metabolic pathways?

    <p>Complex networks of interconnected reactions that lead to metabolic products.</p> Signup and view all the answers

    What is a potential consequence of inherited errors of metabolism?

    <p>Impaired enzyme activity leading to metabolic disturbances.</p> Signup and view all the answers

    Which of the following accurately describes energy capture in metabolism?

    <p>Energy is captured and stored in the form of ATP during both catabolic and anabolic processes.</p> Signup and view all the answers

    What is one way enzyme activity may be regulated in metabolic pathways?

    <p>Rate of enzyme synthesis/degradation</p> Signup and view all the answers

    Which molecules are considered energy-rich monomers in anabolic pathways?

    <p>Glucose, fatty acids, and amino acids</p> Signup and view all the answers

    Which of the following describes a characteristic of catabolic pathways?

    <p>They break down complex molecules into simpler ones</p> Signup and view all the answers

    What defines metabolic intermediates in cellular metabolism?

    <p>They are shared substrates/products in metabolic reactions</p> Signup and view all the answers

    Which statement accurately describes energy coupling reactions?

    <p>They link the synthesis of ATP with energy-releasing reactions</p> Signup and view all the answers

    What role does compartmentalization play in metabolic pathways?

    <p>It separates distinct metabolic processes to avoid interference</p> Signup and view all the answers

    Which of the following is NOT a characteristic of anabolic pathways?

    <p>They break down complex molecules</p> Signup and view all the answers

    What is a common regulatory mechanism for enzymes in metabolic pathways?

    <p>Phosphorylation and dephosphorylation modifications</p> Signup and view all the answers

    What is the primary role of allosteric feedback inhibition in metabolic pathways?

    <p>Inhibit the activity of the first enzyme in the pathway</p> Signup and view all the answers

    What happens to substrate A when enzyme activity is impaired?

    <p>It accumulates in the pathway</p> Signup and view all the answers

    Which process involves breaking down glycogen into glucose?

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

    What is the primary purpose of the Krebs cycle?

    <p>To produce energy in the form of NADH, CO2, and ATP</p> Signup and view all the answers

    Which metabolic process synthesizes glucose from non-carbohydrate sources?

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

    What is a consequence of elevated levels of substrate A in a metabolic pathway?

    <p>Feedback inhibition of the first enzyme</p> Signup and view all the answers

    Which pathway is involved in the biosynthesis of triglycerides?

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

    What type of amino acids metabolize into substrates that can enter gluconeogenesis?

    <p>Glucogenic and ketogenic amino acids</p> Signup and view all the answers

    What role do allosteric inhibitors play in regulating enzyme activity?

    <p>They decrease the activity of enzymes in metabolic pathways</p> Signup and view all the answers

    During which metabolic process do fatty acids undergo step-wise degradation?

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

    What is the result of glycolysis?

    <p>Degradation of glucose to pyruvate</p> Signup and view all the answers

    Which cycle is primarily responsible for producing urea?

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

    What is the primary outcome of anaerobic glycolysis?

    <p>Production of ATP without requiring oxygen</p> Signup and view all the answers

    What is the significance of the hydrolysis of ATP in energy metabolism?

    <p>It releases energy that can drive various biochemical reactions.</p> Signup and view all the answers

    Which of the following statements best describes the role of NADH in metabolism?

    <p>NADH serves as a reducing agent in the electron transport chain.</p> Signup and view all the answers

    During intermediary metabolism, which of the following best describes the conversion processes involved?

    <p>It encompasses the transformation of various biomolecules into energy and structural components.</p> Signup and view all the answers

    What role does oxidative phosphorylation play in cellular respiration?

    <p>It synthesizes ATP and is coupled with the electron transport chain.</p> Signup and view all the answers

    Which process involves the transfer of electrons during the catabolism of substrates?

    <p>The reduction of NAD+ to NADH and FAD to FADH2.</p> Signup and view all the answers

    What is the main role of ATP within metabolic processes?

    <p>To act as a free-energy donor</p> Signup and view all the answers

    Which of the following activities of the organism primarily utilizes energy?

    <p>Active transport of ions</p> Signup and view all the answers

    How are carbohydrates, fatty acids, and proteins ultimately related in metabolism?

    <p>They are metabolized to generate ATP and NADH.</p> Signup and view all the answers

    What is the consequence of impaired enzyme activity in metabolic pathways?

    <p>Accumulation of metabolic intermediates</p> Signup and view all the answers

    Which mechanism is commonly involved in the regulation of metabolic pathways?

    <p>Feedback inhibition of enzymes</p> Signup and view all the answers

    What defines the relationship between catabolism and anabolism?

    <p>Catabolism releases energy, while anabolism consumes it.</p> Signup and view all the answers

    Which of the following best describes metabolism?

    <p>A complex network of interconnected chemical reactions.</p> Signup and view all the answers

    During oxidative phosphorylation, what is primarily generated?

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

    What type of metabolic pathway involves the breakdown of complex molecules into simpler ones?

    <p>Catabolic pathways</p> Signup and view all the answers

    Which of the following statements best distinguishes anabolic pathways from catabolic pathways?

    <p>Anabolic pathways involve the synthesis of complex molecules, while catabolic pathways focus on degradation.</p> Signup and view all the answers

    What is a direct consequence of the interdependence between catabolic and anabolic pathways in metabolism?

    <p>ATP and NADH produced during catabolism can be utilized for anabolic reactions.</p> Signup and view all the answers

    Which of the following characteristics is NOT associated with catabolic pathways?

    <p>They are endergonic in nature.</p> Signup and view all the answers

    Which type of metabolic pathway can be characterized as diverging?

    <p>Pathways that synthesize macromolecules from simple precursors.</p> Signup and view all the answers

    Which statement correctly describes the relationship between anabolic and catabolic pathways?

    <p>Anabolic and catabolic pathways can link through shared metabolic intermediates.</p> Signup and view all the answers

    Which of the following molecules is characterized as an energy-rich metabolic intermediate?

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

    What factor may influence the enzymatic activity in metabolic pathways?

    <p>Rate of enzyme synthesis/degradation</p> Signup and view all the answers

    Which type of molecules are primarily involved as substrates in anabolic pathways?

    <p>Simple organic molecules</p> Signup and view all the answers

    What is a common feature of energy coupling reactions in metabolism?

    <p>They involve ATP hydrolysis and synthesis.</p> Signup and view all the answers

    Which mechanism does NOT directly regulate enzyme activity in metabolic pathways?

    <p>Temperature fluctuations</p> Signup and view all the answers

    Which of the following is an example of a simple organic molecule that serves as a precursor in anabolic pathways?

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

    Which statement about the regulation of metabolic pathways is correct?

    <p>Each enzyme catalyzing a step can be regulated by multiple means.</p> Signup and view all the answers

    What role do allosteric inhibitors play in metabolic pathways?

    <p>They inhibit enzyme activity by binding to sites other than the active site.</p> Signup and view all the answers

    Which metabolic pathway is primarily responsible for synthesizing glucose from non-carbohydrate sources?

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

    What metabolic consequence arises from impaired enzyme activity in a pathway?

    <p>Accumulation of the substrate and deficiency of the product.</p> Signup and view all the answers

    Which of the following processes involves the breakdown of triglycerides into glycerol and fatty acids?

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

    What is a key characteristic of allosteric regulation in metabolic pathways?

    <p>It allows for a rapid response to changes in substrate concentrations.</p> Signup and view all the answers

    Which amino acid metabolism pathway is associated with both glucogenic and ketogenic pathways?

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

    During which metabolic process is energy extracted from NADH to generate ATP?

    <p>Oxidative phosphorylation</p> Signup and view all the answers

    Which term best describes the process of synthesizing fatty acids from acetyl CoA?

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

    What is the primary function of the urea cycle in protein metabolism?

    <p>To convert ammonia into urea for excretion.</p> Signup and view all the answers

    What is the end product of glycolysis?

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

    Which metabolic pathway involves the conversion of glycogen back into glucose?

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

    Which of the following metabolic processes primarily generates NADH?

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

    What is one metabolic outcome of fatty acid oxidation?

    <p>Production of ketone bodies.</p> Signup and view all the answers

    Which metabolic pathway is responsible for the breakdown of proteins into amino acids?

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

    Study Notes

    Metabolism

    • Metabolism is the sum of all chemical processes occurring within an organism that are necessary for life
    • Metabolism is comprised of an integrated network of chemical reactions
    • Many metabolic reactions are concerned with generating or using energy

    Energy Use

    • Energy is required for:
      • Active transport of ions and molecules
      • Performance of mechanical work (muscle contraction, cellular movement)
      • Synthesis of macromolecules and other biomolecules from simple precursors
      • Waste removal

    ATP

    • ATP is the universal currency in the energy exchange economy
    • ATP is formed from the oxidation of food fuel
    • Energy released from fuel compounds is captured in ATP
    • ATP serves as the free-energy donor in most energy-requiring processes

    NADH

    • Carbohydrates, fatty acids, and protein food stuffs generate ATP and NADH
    • Glycolysis, beta-oxidation, TCA cycle, and the electron transport chain are involved in the creation of ATP and NADH

    Hydrolysis and Synthesis of ATP

    • ATP + H2O ↔ ADP + Pi (-30.5kJ/mol)
      • Forward reaction releases energy to drive other reactions
      • Reverse reaction captures energy released from fuel compounds
    • This ATP-ADP cycle is the fundamental mode of energy exchange in biology
    • Most energy-requiring reactions are coupled to ATP hydrolysis

    Redox Reactions

    • Many cellular reactions involve electron exchange
    • NADH is a common currency in redox reactions

    Coupled Redox Reactions

    • During catabolism, hydrogen from substrates is transferred to NAD+ and FAD
    • NADH and FADH2 are reoxidised to NAD+ and FAD by O2 in the electron transport chain located on the inner mitochondrial membrane

    Intermediary Metabolism

    • The metabolic processes involved in the conversion of food to energy, structural and functional components of cells, energy storage, and waste
    • Includes the interconversion of carbohydrates, proteins, and lipids

    Metabolic Pathways

    • Catabolic pathways are degradative, breaking complex molecules down into simple ones and releasing energy (exergonic)
    • Anabolic pathways synthesize molecules, building complex molecules from simple ones, consuming energy (endergonic)
    • ATP and NADH generated in catabolism can be used in anabolic pathways

    Interdependence of Anabolic and Catabolic Pathways

    • Anabolic and catabolic pathways are generally distinct
    • This allows for fine-tuned control and allows both processes to occur simultaneously
    • The pathways are still linked via
      • Energy coupling reactions (ATP hydrolysis/synthesis)
      • Shared metabolic intermediates
      • Shared substrates/products
      • Shared enzymes

    Regulation of Metabolic Pathways

    • Enzymes are key regulators of metabolic pathways
    • Enzyme activity can be regulated by:
      • Rate of enzyme synthesis/degradation
      • Compartmentalization / subcellular localization
      • Modification by another enzyme (phosphorylation/dephosphorylation)
      • Allosteric activators/inhibitors

    Allosteric Feedback Inhibition

    • Metabolic pathways are often regulated by allosteric feedback inhibition
    • The end-product inhibits the activity of an enzyme early in the pathway
      • This usually occurs on the first irreversible step (the committed step)
    • This allows for a rapid response to change in cellular conditions

    Metabolic Consequences of Impaired Enzyme Activity

    • Impaired enzyme activity can lead to:
      • Accumulation of substrate
      • Deficiency of product
      • Diversion to alternate product

    Major Metabolic Pathways and Processes

    • Carbohydrate metabolism
      • Glycolysis
      • Glycogenolysis
      • Gluconeogenesis
      • Glycogen synthesis
      • Hexose monophosphate shunt (pentose phosphate pathway)
    • Protein metabolism
      • Amino acid synthesis
      • Deamination
      • Transamination
      • Urea cycle
      • Ketogenesis
    • Lipid metabolism
      • Beta-oxidation
      • Ketogenesis
      • Lipolysis
      • Fatty acid synthesis
      • Triglyceride synthesis
    • Common pathways
      • Citric acid cycle (Krebs cycle, tricarboxylic acid cycle)
      • Oxidative phosphorylation

    Carbohydrate Metabolism

    • Glycolysis
      • Degradation of glucose to pyruvate
    • Glycogenolysis
      • Degradation of glycogen into glucose
    • Gluconeogenesis
      • Synthesis of glucose from non-carbohydrate sources (e.g., amino acids)
    • Glycogen synthesis
      • Synthesis of glycogen from glucose

    Lipid Metabolism

    • Lipolysis
      • Degradation of triglycerides into glycerol and fatty acids
    • Fatty acid oxidation
      • Step-wise degradation of fatty acids into acetyl CoA
    • Fatty acid synthesis
      • Synthesis of fatty acids from acetyl CoA
    • Lipogenesis
      • Synthesis of triglycerides from glycerol and fatty acids

    Protein Metabolism

    • Proteolysis
      • Degradation of protein into amino acids
    • Protein synthesis
      • Synthesis of protein from amino acids
    • Amino acid catabolism
      • Degradation of amino acids into amino group and carbon backbone
    • Amino acid synthesis
      • Synthesis of amino acids by transamination of metabolic intermediates

    Intermediary Metabolism

    • All of these processes are interconnected and utilize shared intermediates.

    Metabolism

    • Metabolism is the sum of all the chemical reactions in an organism that are necessary for life.
    • Many metabolic reactions are related to energy generation or use.
    • Organisms use energy for:
      • Active transport of ions and molecules
      • Mechanical work, for example, muscle contraction
      • Synthesis of macromolecules, such as DNA, RNA, and proteins
      • Removal of waste products

    ATP is the Energy Currency

    • Some reactions require energy, while others release energy. Energy can be transferred between reactions.
    • Reactions need a common currency for energy exchange. This currency is ATP (adenosine triphosphate).
    • ATP is formed from the oxidation of consumed food (fuel).
    • Energy released from fuel compounds is captured in ATP.
    • ATP is used as the free-energy donor in most processes that require energy.

    Energy Production

    • Carbohydrates, fatty acids, and proteins are metabolized, either directly or indirectly, to generate ATP and NADH.
    • The pathways involved in this process include:
      • Glycolysis
      • Beta-oxidation
      • The TCA cycle
      • Electron transport coupled to oxidative phosphorylation

    ATP Hydrolysis and Synthesis

    • ATP + H2O ↔ ADP + Pi (ΔG = -30.5 kJ/mol)
    • The forward reaction releases energy.
    • The reverse reaction captures energy.
    • The ATP-ADP cycle is the fundamental mode of energy exchange in biology.
    • ATP hydrolysis is generally coupled with most energy-requiring reactions.
    • A coupled reaction, for example:
      • Glucose + Pi --> Glucose-6-Phosphate + H2O (ΔG = +13.8 kJ/mol)
      • ATP + H2O --> ADP + Pi (ΔG = -30.5 kJ/mol)
      • When combined, the energy from ATP hydrolysis drives the synthesis of glucose-6-phosphate.

    Redox Reactions

    • Many cellular reactions involve the exchange of electrons. NADH is a common currency in these reactions.
    • NAD+ (Nicotinamide Adenine Dinucleotide) is a cofactor that plays a crucial role in redox reactions.

    Coupled Redox Reactions:

    • During catabolism, hydrogen from the substrate is transferred to NAD+ and FAD.
    • NADH and FADH2 are reoxidized to NAD+ and FAD by oxygen (O2) in the electron transport chain located in the inner mitochondrial membrane.

    Intermediary Metabolism

    • Intermediary metabolism refers to metabolic processes converting food into energy.
    • It involves the conversion of carbohydrates, proteins, and lipids into energy, structural components of the cell, energy storage, and waste.

    Classification of Metabolic Pathways

    • Metabolic pathways can be categorized as catabolic or anabolic:
      • Catabolic: Degradation of molecules from complex to simple; exergonic (energy releasing).
      • Anabolic: Synthesis of molecules from simple to complex; endergonic (energy requiring).
    • ATP and NADH produced in catabolism are used for anabolic reactions.
    • Monomers released from polymers provide building blocks for the synthesis of other macromolecules.
    • There are three types of metabolic pathways:
      • Converging: Usually catabolic (e.g., multiple starting molecules converge into one final product).
      • Diverging: Usually anabolic (e.g., one starting molecule diverges into multiple products).
      • Cyclic: Involve reactions in a cycle (e.g., TCA cycle).

    Anabolic and Catabolic Pathway Interdependence and Independence

    • Synthetic and degradative pathways are generally distinct, allowing for better control.
    • Both processes can occur at the same time but often in different cells.
    • Synthetic and degradative pathways are linked by:
      • Energy coupling reactions (ATP hydrolysis/synthesis)
      • Shared metabolic intermediates
      • Shared substrates and products
      • Shared enzymes

    Regulation of Metabolic Pathways

    • Each step of a metabolic pathway is catalyzed by a specific enzyme.
    • Enzyme activity is regulated in several ways:
      • Rate of enzyme synthesis and degradation
      • Compartmentalization or subcellular localization
      • Modification by another enzyme (e.g., phosphorylation and dephosphorylation)
      • Allosteric activators and inhibitors

    Allosteric Feedback Inhibition

    • Metabolic pathways often use allosteric feedback inhibition.
    • The end product of a pathway inhibits the activity of an enzyme at or near the beginning of the pathway.
    • This enzyme usually catalyzes the first irreversible step (committed step) in the pathway.
    • This allows for a rapid response to changes.

    Cellular Homeostasis

    • Regulation of metabolic pathways is crucial for cellular homeostasis.
    • Organisms maintain cells in a steady state.
    • When homeostasis is disturbed, changes are made to return the cell to a normal state.

    Metabolic Consequences of Impaired Enzyme Activity

    • An impaired enzyme can lead to:
      • Accumulation of the substrate.
      • Deficiency of the product.
      • Diversion to an alternative product.

    Major Metabolic Pathways and Processes

    Carbohydrate Metabolism

    • Includes:
      • Glycolysis (degradation of glucose to pyruvate)
      • Glycogenolysis (degradation of glycogen)
      • Gluconeogenesis (synthesis of glucose from non-carbohydrate sources)
      • Glycogen synthesis (glycogenesis, synthesis of glycogen from glucose)
      • Anaerobic glycolysis (when oxygen is limited)
      • Hexose monophosphate shunt (pentose phosphate pathway)

    Protein Metabolism

    • Includes:
      • Amino acid synthesis
      • Deamination
      • Transamination
      • Urea cycle
      • Ketogenesis

    Lipid Metabolism

    • Includes:
      • Beta-oxidation (degradation of fatty acids)
      • Ketogenesis
      • Lipolysis (degradation of triglycerides)
      • Fatty acid synthesis
      • Triglyceride synthesis

    Common Pathways

    • Includes:
      • Citric acid cycle (Krebs cycle, tricarboxylic acid cycle): Oxidation of acetyl CoA to CO2, H2O, and NADH
      • Oxidative phosphorylation: Extraction of energy from NADH to generate ATP

    Specific Pathways

    Carbohydrate Metabolism Explained

    • Glycolysis: The breakdown of glucose into pyruvate, producing a small amount of ATP and NADH.
    • Glycogenolysis: The breakdown of glycogen, a stored form of glucose, releasing glucose into the blood.
    • Gluconeogenesis: The synthesis of glucose from non-carbohydrate sources, such as amino acids, lactate, or glycerol, when glucose levels are low.
    • Glycogen synthesis (glycogenesis): The synthesis of glycogen from glucose, storing excess glucose for later use.
    • Anaerobic glycolysis: The breakdown of glucose in the absence of oxygen, producing lactate as a byproduct.
    • Hexose monophosphate shunt (pentose phosphate pathway): Produces NADPH, a reducing agent, and ribose-5-phosphate, a precursor for nucleotide synthesis.

    Lipid Metabolism Explained

    • Lipolysis: The breakdown of triglycerides into glycerol and fatty acids.
    • Fatty acid oxidation: The stepwise breakdown of fatty acids into acetyl-CoA, which can enter the Krebs cycle.
    • Fatty acid synthesis: The synthesis of fatty acids from acetyl-CoA.
    • Glycerol synthesis: Synthesis of glycerol from glycolytic intermediates.
    • Lipogenesis: The synthesis of triglycerides from glycerol and fatty acids.

    Protein Metabolism Explained

    • Proteolysis: The breakdown of proteins into amino acids.
    • Protein synthesis: The synthesis of proteins from amino acids.
    • Amino acid catabolism: The breakdown of amino acids into amino groups (nitrogen) and carbon backbones.
    • Transamination: The transfer of an amino group from one amino acid to another to form a new amino acid.
    • Urea cycle: The cycle that eliminates nitrogenous waste (ammonia) from the body in the form of urea.

    Intermediary Metabolism Diagram

    • A diagram illustrates how protein, glycogen, and triglycerides are interconnected through various metabolic pathways. They share common intermediates, including glucose, pyruvate, acetyl-CoA, and utilize pathways such as glycolysis, gluconeogenesis, and the Krebs cycle.
    • This shows the crucial interdependence of these metabolic pathways.

    Further Resources

    • Suggested texts for further learning:
      • Lippincott Illustrated Reviews: Biochemistry
      • Marks' Basic Medical Biochemistry: A Clinical Approach

    Metabolism

    • The sum of all chemical processes within an organism.
    • Involves an integrated network of chemical reactions.
    • Many reactions are concerned with generating or using energy.

    Cellular Energy Use

    • Active transport of ions and molecules.
    • Performance of mechanical work like muscle contraction.
    • Synthesis of macromolecules from simple precursors.
    • Waste removal.

    ATP: The Energy Currency

    • Some reactions require energy, while others release energy.
    • ATP is the common currency for energy transfer.
    • Formed from the oxidation of food fuel.
    • Energy released from fuel compounds is captured in ATP molecules.
    • Acts as the energy donor in most energy-requiring processes.

    NADH: Electron Carrier

    • NADH is a common currency for redox reactions.
    • Involved in releasing the energy from fuel compounds for ATP generation.

    Intermediary Metabolism

    • Converts food into energy, structural and functional cellular components, energy storage and waste products.
    • Includes interconversion of carbohydrates, proteins and lipids.

    Metabolic Pathways

    • Catabolic: Degradation of molecules from complex to simple, energy releasing (exergonic).
    • Anabolic: Synthesis of molecules from simple to complex, energy requiring (endergonic).
    • Converging: Catabolic pathways.
    • Diverging: Anabolic pathways.
    • Cyclic: Pathways with intermediates cycling.

    Anabolic & Catabolic Pathway Interdependencies

    • Often distinct, allowing for independent control of processes.
    • Linked by energy coupling reactions (ATP hydrolysis/synthesis), shared metabolic intermediates, substrates/products, and enzymes.

    Regulation of Metabolic Pathways

    • Each step is catalyzed by a specific enzyme.
    • Regulating enzyme activity:
      • Rate of enzyme synthesis/degradation.
      • Compartmentalization/subcellular localization.
      • Modification by another enzyme (e.g. phosphorylation/dephosphorylation).
      • Allosteric activators/inhibitors.

    Allosteric Feedback Inhibition

    • End product of the pathway inhibits an enzyme at or near the start.
    • Often regulates the first, irreversible step (committed step) of a pathway.
    • Allows for rapid response to change.

    Cellular Homeostasis

    • Maintaining a steady state within the cell.
    • Regulation of metabolic pathways is essential for this.
    • When steady-state is disturbed, changes are made to restore normal conditions.

    Impaired Enzyme Activity

    • Accumulation of substrate.
    • Deficiency of product.
    • Diversion to alternate product.

    Major Metabolic Pathways & Processes

    • Carbohydrate Metabolism: Glycolysis, glycogenolysis, gluconeogenesis, glycogen synthesis, anaerobic glycolysis, hexose monophosphate shunt (pentose phosphate pathway).
    • Protein Metabolism: Amino acid synthesis, deamination, transamination, urea cycle, ketogenesis.
    • Lipid Metabolism: β-oxidation, ketogenesis, lipolysis, fatty acid synthesis, triglyceride synthesis.
    • Common Processes: Citric acid cycle (Krebs cycle, tricarboxylic acid cycle), oxidative phosphorylation.

    Carbohydrate Metabolism

    • Glycolysis: Degrades glucose to pyruvate.
    • Glycogenolysis: Degrades glycogen into glucose.
    • Gluconeogenesis: Synthesizes glucose from non-carbohydrate sources.
    • Glycogen Synthesis: Synthesizes glycogen from glucose.

    Lipid Metabolism

    • Lipolysis: Degrades triglycerides into glycerol and fatty acids.
    • Fatty Acid Oxidation: Degrades fatty acids into acetyl CoA for the Krebs cycle.
    • Fatty Acid Synthesis: Synthesizes fatty acids from acetyl CoA.
    • Lipogenesis: Synthesizes triglycerides from glycerol and fatty acids.

    Protein Metabolism

    • Proteolysis: Degrades protein into amino acids.
    • Protein Synthesis: Synthesizes proteins from amino acids.
    • Deamination: Removes amino group from amino acids.
    • Transamination: Transfers amino groups between molecules.
    • Urea Cycle: Eliminates excess nitrogen as urea.

    Intermediary Metabolism Map

    • Shows the interconnectedness of carbohydrate, protein and lipid metabolism.

    Further Resources

    • Lippincott Illustrated Reviews: Biochemistry
    • Marks' Basic Medical Biochemistry: A Clinical Approach

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    Introduction to Metabolism 2022 PDF

    Description

    This quiz covers the key concepts of metabolism, focusing on the chemical processes necessary for life. It explores the roles of ATP and NADH in energy exchange, as well as the mechanisms of energy use in cellular activities. Test your understanding of how these processes interconnect to sustain life.

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