Biology Chapter: Metabolism and Energy
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Questions and Answers

What is the sum total of an organism's chemical reactions called?

  • Metabolism (correct)
  • Cellular respiration
  • Metabolic pathway
  • Bioenergetics

Which of the following accurately describes catabolic pathways?

  • They release energy by breaking down complex molecules. (correct)
  • They primarily generate oxygen during respiration.
  • They store energy for future use in reactions.
  • They build complex molecules from simpler ones.

In what way do anabolic pathways specifically function?

  • They are less efficient than catabolic pathways.
  • They consume energy to build complex molecules. (correct)
  • They primarily occur in the absence of oxygen.
  • They release energy during breakdown of molecules.

What is defined as the study of how energy flows through living organisms?

<p>Bioenergetics (A)</p> Signup and view all the answers

What role do enzymes play in metabolic pathways?

<p>They catalyze specific steps of the pathway. (A)</p> Signup and view all the answers

Which statement about energy in metabolic processes is correct?

<p>Energy released from catabolic reactions drives anabolic reactions. (B)</p> Signup and view all the answers

What is a characteristic of metabolic pathways?

<p>They are organized into sequential steps. (B)</p> Signup and view all the answers

Which statement correctly describes energy in the context of cellular metabolism?

<p>Energy capacity enables cells to perform work. (D)</p> Signup and view all the answers

Which type of energy is associated with the relative motion of objects?

<p>Kinetic energy (A)</p> Signup and view all the answers

What form of potential energy is exemplified by water stored behind a dam?

<p>Gravitational potential energy (A)</p> Signup and view all the answers

During which type of reaction is potential energy released as usable energy?

<p>Catabolic reaction (C)</p> Signup and view all the answers

How does heat transfer primarily occur between systems?

<p>From warmer to cooler bodies (B)</p> Signup and view all the answers

What does the first law of thermodynamics state?

<p>Energy can be transformed but not created or destroyed (A)</p> Signup and view all the answers

What is entropy a measure of?

<p>Disorder or randomness in a system (D)</p> Signup and view all the answers

What is a characteristic of an isolated system?

<p>Cannot exchange energy or matter (C)</p> Signup and view all the answers

What process requires an input of energy to occur?

<p>Nonspontaneous processes (A)</p> Signup and view all the answers

What happens to ordered forms of energy during most energy transformations?

<p>They are converted to heat (D)</p> Signup and view all the answers

In biological systems, what must occur for spontaneous processes to take place?

<p>They must increase the total entropy of the universe (D)</p> Signup and view all the answers

Which type of energy transformation occurs when a person dives into water?

<p>Potential to kinetic energy (C)</p> Signup and view all the answers

How does an organism create ordered structures from less ordered inputs?

<p>By transforming energy and matter from surroundings (D)</p> Signup and view all the answers

What primarily limits the usefulness of heat as an energy source within living cells?

<p>Constant temperature throughout cell structures (B)</p> Signup and view all the answers

How does water naturally flow in terms of energy?

<p>Downhill with no energy input (B)</p> Signup and view all the answers

What is indicated by a negative value of ΔG in a reaction?

<p>The reaction occurs without an input of energy. (C), The reaction is moving toward equilibrium. (D)</p> Signup and view all the answers

Which of the following statements about exergonic and endergonic reactions is true?

<p>Endergonic reactions require energy to proceed. (D)</p> Signup and view all the answers

In which condition does a cell reach metabolic equilibrium?

<p>When the rates of forward and backward reactions are equal. (A)</p> Signup and view all the answers

What does a positive ΔG indicate about a reaction?

<p>It is nonspontaneous and requires energy input. (B)</p> Signup and view all the answers

During cellular respiration, the breakdown of glucose generates how much energy available for work?

<p>686 kcal/mol (D)</p> Signup and view all the answers

Which of the following correctly defines a spontaneous process?

<p>A process that occurs without external energy input. (A)</p> Signup and view all the answers

What is the effect of decreasing enthalpy on the spontaneity of a reaction?

<p>It increases the spontaneity of the reaction. (C)</p> Signup and view all the answers

Which of the following accurately describes metabolic disequilibrium?

<p>It is critical for ongoing cellular work. (D)</p> Signup and view all the answers

Which variable in the equation ΔG = ΔH - TΔS represents absolute temperature?

<p>T (D)</p> Signup and view all the answers

What is the relationship between free energy and stability in a system?

<p>Systems with less free energy are more stable. (C)</p> Signup and view all the answers

What is the ultimate fate of a cell that reaches metabolic equilibrium?

<p>It is considered dead and cannot do work. (B)</p> Signup and view all the answers

How does the process of photosynthesis relate to cellular respiration?

<p>Photosynthesis stores energy, while respiration releases it. (D)</p> Signup and view all the answers

What role do substrates play in cellular work?

<p>They are essential for sustaining metabolic disequilibrium. (B)</p> Signup and view all the answers

What is primarily responsible for energy coupling in cells?

<p>ATP (C)</p> Signup and view all the answers

What is the consequence of breaking the terminal phosphate bond of ATP?

<p>Release of energy (D)</p> Signup and view all the answers

Which statement about the bonds in ATP is correct?

<p>They are considered fairly weak covalent bonds. (D)</p> Signup and view all the answers

What role does a phosphorylated intermediate play in cellular processes?

<p>It increases the reactivity of the molecule it is attached to. (C)</p> Signup and view all the answers

During the hydrolysis of ATP, what happens to the free energy?

<p>It decreases as ATP is converted to ADP. (A)</p> Signup and view all the answers

What provides the energy for the regeneration of ATP from ADP within the cell?

<p>Exergonic (catabolic) reactions (A)</p> Signup and view all the answers

What is the initial investment of energy needed to start a chemical reaction called?

<p>Activation energy (D)</p> Signup and view all the answers

How do enzymes speed up metabolic reactions?

<p>By lowering activation energy. (A)</p> Signup and view all the answers

Why is ATP referred to as a renewable resource?

<p>It can be continuously regenerated from ADP. (D)</p> Signup and view all the answers

What significant feature of ATP contributes to its instability?

<p>The crowding of negatively charged phosphate groups. (A)</p> Signup and view all the answers

What occurs to ATP during mechanical work involving motor proteins?

<p>ATP is hydrolyzed leading to shape changes in the protein. (B)</p> Signup and view all the answers

What do plants use to produce ATP apart from catabolic reactions?

<p>Light energy via photosynthesis (B)</p> Signup and view all the answers

What key role does thermal energy play in reactant molecules?

<p>It helps break bonds so that reactions can occur. (B)</p> Signup and view all the answers

What characterizes the process of ATP hydrolysis within the cell?

<p>It releases free energy resulting from bond breaking. (C)</p> Signup and view all the answers

What is the primary factor determining the rate of an enzyme-catalyzed reaction when the enzyme is saturated?

<p>Speed of the active site conversion (D)</p> Signup and view all the answers

What happens to an enzyme at temperatures above its optimal range?

<p>The enzyme undergoes denaturation (B)</p> Signup and view all the answers

How does competitive inhibition affect enzyme activity?

<p>It can be reversed by increasing substrate concentration (C)</p> Signup and view all the answers

Which of the following enzymes works best at a pH of 8?

<p>Trypsin (D)</p> Signup and view all the answers

What role do cofactors play in enzyme activity?

<p>They assist in catalytic activity (C)</p> Signup and view all the answers

What characterizes irreversible enzyme inhibitors?

<p>They bind covalently, altering the enzyme permanently (C)</p> Signup and view all the answers

What is the significance of a mutation in an enzyme's active site?

<p>It might allow the enzyme to bind to a different substrate (A)</p> Signup and view all the answers

What effect does allosteric regulation have on an enzyme?

<p>It affects enzyme activity at a site distinct from the active site (C)</p> Signup and view all the answers

What compound is known for binding to the active site of bacterial enzymes to inhibit cell wall synthesis?

<p>Penicillin (D)</p> Signup and view all the answers

What occurs during the transition state of a reaction?

<p>The reactants have absorbed enough energy for bonds to break. (B)</p> Signup and view all the answers

What feature distinguishes thermophilic enzymes from human enzymes?

<p>Thermophilic enzymes function best at much higher temperatures (B)</p> Signup and view all the answers

How does an enzyme affect the activation energy of a reaction?

<p>It lowers the activation energy needed to reach the transition state. (A)</p> Signup and view all the answers

Which of the following is a common characteristic of metabolic control through enzyme inhibitors?

<p>Inhibitors can be either natural or synthetic (A)</p> Signup and view all the answers

What is the primary reason enzymes can be highly specific to certain substrates?

<p>Their three-dimensional shape allows specific interactions with substrates. (B)</p> Signup and view all the answers

What happens to enzyme activity in the presence of a noncompetitive inhibitor?

<p>The enzyme conformation is altered, reducing activity (A)</p> Signup and view all the answers

What occurs when substrate concentration is low?

<p>An increase in substrate concentration enhances the reaction rate. (A)</p> Signup and view all the answers

What is a primary method researchers have used to understand enzyme evolution?

<p>Introducing random mutations and selecting favorable traits (A)</p> Signup and view all the answers

What characterizes the active site of an enzyme?

<p>It is typically formed by a few specific amino acids that catalyze reactions. (D)</p> Signup and view all the answers

Which statement about enzymes and vitamins is true?

<p>Many vitamins function as coenzymes (C)</p> Signup and view all the answers

What does the term induced fit refer to in enzyme activity?

<p>The change in shape of the enzyme upon substrate binding to facilitate the reaction. (B)</p> Signup and view all the answers

What results from a decrease in pH for most enzymes?

<p>Denaturation and loss of function at extreme pH (D)</p> Signup and view all the answers

Enzymes are typically not affected by the reaction they catalyze. Which statement best explains this?

<p>Enzymes remain chemically unchanged and are reusable even after extensive catalysis. (C)</p> Signup and view all the answers

What might prevent a reaction from proceeding even if reactants have sufficient energy?

<p>The reactants being at low temperature without sufficient thermal energy. (B)</p> Signup and view all the answers

What process is indicated when a spark plug releases energy to initiate combustion?

<p>Activation energy provision through heat. (B)</p> Signup and view all the answers

Which of the following best describes the role of R groups in an enzyme's active site?

<p>They may participate in the catalysis by forming covalent bonds with the substrate. (C)</p> Signup and view all the answers

How do enzymes speed up reactions involving more than one reactant?

<p>By bringing reactants together in the correct orientation at the active site. (A)</p> Signup and view all the answers

What happens during the bond-forming phase of a reaction, according to free energy changes?

<p>Energy is released as reactants are converted into products. (B)</p> Signup and view all the answers

Which statement regarding metabolic enzymes is correct?

<p>They can catalyze both forward and reverse reactions depending on reactant and product concentrations. (C)</p> Signup and view all the answers

What limitation occurs when active sites on all enzymes are engaged?

<p>The reaction rate cannot increase any further regardless of substrate availability. (B)</p> Signup and view all the answers

What is a primary function of aerobic respiration in organisms?

<p>To produce energy in the form of ATP using oxygen (D)</p> Signup and view all the answers

What type of reaction occurs when glucose is oxidized in cellular respiration?

<p>Redox reaction (C)</p> Signup and view all the answers

Which statement accurately describes the process of electron transport in cellular respiration?

<p>Electrons are passed to NAD+ before reaching oxygen (B)</p> Signup and view all the answers

In the context of aerobic respiration, what role do coenzymes like NAD+ play?

<p>They accept electrons from glucose during oxidation (A)</p> Signup and view all the answers

What is the significance of the activation energy barrier in cellular respiration?

<p>It ensures that reactions occur in a stepwise manner, controlled by enzymes. (A)</p> Signup and view all the answers

Which product results from the complete oxidation of one mole of glucose in cellular respiration?

<p>Six moles of CO2, six moles of H2O, and energy (D)</p> Signup and view all the answers

What happens to the potential energy of electrons during cellular respiration?

<p>Electrons lose potential energy as they are transferred to more electronegative partners. (C)</p> Signup and view all the answers

Which of the following substances can be utilized as fuel for aerobic respiration?

<p>Carbohydrates, fats, and proteins (A)</p> Signup and view all the answers

When methane reacts with oxygen, what type of reaction is it an example of?

<p>Combustion (D)</p> Signup and view all the answers

What characterizes the process of anaerobic respiration in prokaryotes?

<p>It uses alternatives to oxygen for the reaction. (A)</p> Signup and view all the answers

How does sodium behave in the formation of table salt from sodium and chloride?

<p>It donates electrons and is oxidized. (B)</p> Signup and view all the answers

What is a major source of energy released during the oxidation of organic fuel molecules?

<p>The movement of electrons releases energy. (A)</p> Signup and view all the answers

What is the result of an exergonic reaction like glucose catabolism?

<p>Energy is released and used to generate ATP. (A)</p> Signup and view all the answers

What is the primary function of NAD + during cellular respiration?

<p>To trap the released electrons (C)</p> Signup and view all the answers

What defines redox reactions in the context of cellular respiration?

<p>They involve the transfer of electrons between reactants. (B)</p> Signup and view all the answers

How many NADH molecules are yielded from one glucose molecule during glycolysis?

<p>2 (D)</p> Signup and view all the answers

Which of the following stages generates ATP via oxidative phosphorylation?

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

What is the initial substrate for glycolysis?

<p>Glucose (A)</p> Signup and view all the answers

What happens to each NAD + molecule during the oxidation of glucose?

<p>It is reduced to NADH (B)</p> Signup and view all the answers

In which cellular location does glycolysis take place?

<p>Cytosol (A)</p> Signup and view all the answers

What is the role of the electron transport chain in cellular respiration?

<p>To transfer electrons from NADH to oxygen (B)</p> Signup and view all the answers

What role does an activator play in allosteric regulation of enzymes?

<p>It increases the enzyme’s catalytic activity by stabilizing the active conformation. (A)</p> Signup and view all the answers

What is the primary function of cooperativity in allosteric enzymes?

<p>To amplify the response of the enzyme to substrates. (D)</p> Signup and view all the answers

What characterizes the energy investment phase of glycolysis?

<p>The cell consumes ATP (B)</p> Signup and view all the answers

How does feedback inhibition benefit a metabolic pathway?

<p>It prevents overproduction of the end product by inhibiting early enzymes. (B)</p> Signup and view all the answers

How does oxidative phosphorylation differ from substrate-level phosphorylation?

<p>Substrate-level phosphorylation directly forms ATP from ADP (C)</p> Signup and view all the answers

What is the consequence of NADH carrying electrons down an energy gradient to oxygen?

<p>Water is produced as a byproduct (A)</p> Signup and view all the answers

What is the significance of allosteric regulation in pharmaceutical applications?

<p>They can regulate enzyme activity without competing with substrates. (A)</p> Signup and view all the answers

What is the primary outcome of ATP hydrolysis in terms of metabolic pathways?

<p>It inhibits catabolic enzymes by reducing substrate affinity. (A)</p> Signup and view all the answers

Which statement accurately describes pyruvate in cellular respiration?

<p>It is used for the citric acid cycle after glycolysis (B)</p> Signup and view all the answers

What is the electronegative receptor at the bottom of the electron transport chain?

<p>Oxygen (B)</p> Signup and view all the answers

Which factor most significantly contributes to the regulation of metabolic pathways?

<p>Cellular compartmentalization and enzyme localization. (B)</p> Signup and view all the answers

Which statement accurately describes the role of hemoglobin in cooperativity?

<p>The binding of oxygen at multiple sites enhances the overall affinity for oxygen. (B)</p> Signup and view all the answers

How are the protons released during the oxidation of glucose by dehydrogenase enzymes?

<p>They are released into the surrounding solution as H + (D)</p> Signup and view all the answers

What is the role of enzymes in catabolic pathways?

<p>They catalyze the degradation of organic molecules into simpler forms. (C)</p> Signup and view all the answers

What is the typical energy yield of ATP from one molecule of glucose during respiration?

<p>32 ATP (A)</p> Signup and view all the answers

What characterizes the metabolic process of fermentation compared to aerobic respiration?

<p>Fermentation leads to partial degradation of sugars without oxygen. (A)</p> Signup and view all the answers

How do metabolic enzymes function as part of a multienzyme complex?

<p>They coordinate reactions where products sequentially become substrates for adjacent enzymes. (C)</p> Signup and view all the answers

What is the implication of allosteric sites being distinct among enzymes?

<p>It provides a target for highly specific drug design. (A)</p> Signup and view all the answers

What is the result of changes in cellular conditions on allosteric regulation?

<p>They can lead to the stabilization of either active or inactive enzyme forms. (B)</p> Signup and view all the answers

What effect does ADP have on catabolic enzymes as opposed to ATP?

<p>ADP functions as an activator enhancing enzyme activity. (D)</p> Signup and view all the answers

What is the maximum ATP yield from one glucose molecule during cellular respiration if the less efficient shuttle is functioning?

<p>30 ATP (D)</p> Signup and view all the answers

How many ATP are theoretically generated from each NADH that donates its electrons to mitochondrial NAD+ in liver cells?

<p>3 ATP (A)</p> Signup and view all the answers

What adaptation allows hibernating mammals to generate heat without producing ATP?

<p>Uncoupling protein activation (C)</p> Signup and view all the answers

What by-product is produced during anaerobic respiration in sulfate-reducing bacteria?

<p>Hydrogen sulfide (A)</p> Signup and view all the answers

What is the efficiency of respiration based on the complete oxidation of glucose?

<p>34% (B)</p> Signup and view all the answers

What must occur to maintain glycolysis during fermentation?

<p>Recycling of NAD+ (C)</p> Signup and view all the answers

Which of the following statements about fermentation is true?

<p>Fermentation occurs when NADH donates electrons to pyruvate. (A)</p> Signup and view all the answers

During alcoholic fermentation, what is the first conversion step of pyruvate?

<p>Conversion to acetaldehyde (D)</p> Signup and view all the answers

What drives the uptake of pyruvate into the mitochondrion?

<p>Proton-motive force (D)</p> Signup and view all the answers

Which type of enzyme is crucial for the conversion of pyruvate to lactate during lactic acid fermentation?

<p>Lactate dehydrogenase (C)</p> Signup and view all the answers

What is the role of FAD when receiving electrons in the context of cellular respiration?

<p>Generating more ATP than NADH (D)</p> Signup and view all the answers

What is produced as a by-product during lactic acid fermentation?

<p>Lactate (B)</p> Signup and view all the answers

How do fermentation and anaerobic respiration differ?

<p>Anaerobic respiration involves electron transport chains. (A)</p> Signup and view all the answers

Which effect does the presence of an uncoupling protein have on the overall ATP production?

<p>Causes heat generation without ATP production (B)</p> Signup and view all the answers

What is the primary outcome of the conversion of pyruvate to acetyl CoA?

<p>Formation of high-energy acetyl CoA (D)</p> Signup and view all the answers

How many molecules of NADH are produced per acetyl group that enters the citric acid cycle?

<p>3 (B)</p> Signup and view all the answers

What is the role of FAD in the citric acid cycle?

<p>It accepts electrons in a specific step (C)</p> Signup and view all the answers

During oxidative phosphorylation, what is the main function of the electron transport chain?

<p>It synthesizes ATP from ADP and inorganic phosphate (C)</p> Signup and view all the answers

What is the significance of the regeneration of oxaloacetate in the citric acid cycle?

<p>It allows the cycle to continue repeatedly (A)</p> Signup and view all the answers

Which of the following statements about ATP production is true?

<p>Most ATP is produced through oxidative phosphorylation (A)</p> Signup and view all the answers

Where does the citric acid cycle occur in prokaryotic cells?

<p>In the cytoplasm (D)</p> Signup and view all the answers

What is the primary purpose of acetyl CoA in cellular respiration?

<p>To enter the citric acid cycle for further oxidation (A)</p> Signup and view all the answers

What is released during the carboxyl group removal in pyruvate conversion?

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

How many ATP equivalents are produced from one turn of the citric acid cycle?

<p>1 (C)</p> Signup and view all the answers

Which of these is NOT a component of the electron transport chain?

<p>Glucose (B)</p> Signup and view all the answers

What does the reduction of NAD+ during cellular respiration result in?

<p>The formation of NADH (D)</p> Signup and view all the answers

Which term is synonymous with the citric acid cycle?

<p>Krebs cycle (B)</p> Signup and view all the answers

Why is the interior mitochondrial membrane highly folded?

<p>To increase the surface area for the electron transport chain (D)</p> Signup and view all the answers

What is the primary consequence of anaerobic conditions in human muscle cells during exercise?

<p>Switch from aerobic respiration to lactic acid fermentation (C)</p> Signup and view all the answers

Which molecule acts as the final electron acceptor in fermentation processes?

<p>Pyruvate or acetaldehyde (C)</p> Signup and view all the answers

How do facultative anaerobes differ from obligate anaerobes in their metabolic processes?

<p>Facultative anaerobes can switch between fermentation and respiration. (C)</p> Signup and view all the answers

What is the net ATP yield from glycolysis in all three pathways of ATP production?

<p>2 ATP (B)</p> Signup and view all the answers

Why is the transfer of electrons from NADH to the electron transport chain significant in cellular respiration?

<p>It regenerates NAD+ and releases energy for ATP synthesis. (D)</p> Signup and view all the answers

What impact does oxygen have on the process of cellular respiration compared to fermentation?

<p>Oxygen facilitates a higher ATP yield due to oxidative phosphorylation. (C)</p> Signup and view all the answers

What occurs to lactate once it is produced during anaerobic respiration in human muscle cells?

<p>It is transported to the liver for conversion back to pyruvate. (B)</p> Signup and view all the answers

What must occur to proteins before they can enter the cellular respiration pathways?

<p>Their amino groups must be removed through deamination. (C)</p> Signup and view all the answers

Which statement accurately describes the metabolic pathways available in organisms?

<p>Facultative anaerobes can adapt their metabolic pathways based on oxygen presence. (D)</p> Signup and view all the answers

What distinguishes aerobic from anaerobic respiration in terms of final electron acceptors?

<p>Aerobic respiration uses oxygen; anaerobic uses a less electronegative molecule. (C)</p> Signup and view all the answers

What is a potential energy yield difference between aerobic respiration and fermentation?

<p>Aerobic respiration can yield up to 32 ATP per glucose molecule. (B)</p> Signup and view all the answers

What metabolic pathway is considered to have evolved very early in the history of life on Earth?

<p>Glycolysis (D)</p> Signup and view all the answers

What is the main reason facultative anaerobes must consume glucose at a faster rate when relying on fermentation?

<p>Fermentation generates less ATP than aerobic respiration. (B)</p> Signup and view all the answers

How does the carbon skeleton of amino acids enter the metabolic pathways for ATP production?

<p>By being transformed into intermediates of glycolysis or the citric acid cycle. (B)</p> Signup and view all the answers

What is the primary function of the electron transport chain in cellular respiration?

<p>To generate a proton gradient for ATP synthesis (D)</p> Signup and view all the answers

Which component of the electron transport chain directly delivers electrons to oxygen?

<p>Cytochrome a3 (A)</p> Signup and view all the answers

How does ATP synthase generate ATP?

<p>By utilizing the energy from an existing ion gradient (D)</p> Signup and view all the answers

Why do FADH2 electrons contribute to less ATP production compared to NADH?

<p>The electrons from FADH2 are at a lower energy level. (A)</p> Signup and view all the answers

What is chemiosmosis primarily responsible for in cellular respiration?

<p>Synthesis of ATP from ADP and phosphate (D)</p> Signup and view all the answers

What role does the heme group play in cytochromes?

<p>It acts as an electron acceptor and donor. (A)</p> Signup and view all the answers

How does the proton-motive force contribute to ATP production?

<p>It drives protons back across the membrane through ATP synthase. (D)</p> Signup and view all the answers

What is the significance of the spatial arrangement of electron carriers in the membrane?

<p>It minimizes energy losses during electron transfer. (B)</p> Signup and view all the answers

What is the relationship between redox reactions and ATP synthesis?

<p>Redox reactions progressively release energy that aids in ATP synthesis. (C)</p> Signup and view all the answers

How does the electron transport chain maintain the H+ gradient?

<p>By using the exergonic flow of electrons to pump protons across the membrane. (C)</p> Signup and view all the answers

What is the role of substrate-level phosphorylation in ATP production?

<p>It produces a limited amount of ATP during glycolysis and the citric acid cycle. (B)</p> Signup and view all the answers

What drives the flow of protons through ATP synthase?

<p>A difference in H+ concentrations across the membrane. (A)</p> Signup and view all the answers

What is a key distinction between chemiosmosis in mitochondria and chloroplasts?

<p>Light energy drives proton gradient formation only in chloroplasts. (D)</p> Signup and view all the answers

Which factor affects the ratio of NADH to ATP production during cellular respiration?

<p>The direct coupling of phosphorylation and redox reactions. (D)</p> Signup and view all the answers

Flashcards

Metabolism

The sum of all chemical reactions that occur within a living organism.

Metabolic Pathways

Metabolic pathways are a series of steps, each with a specific enzyme, that transform a starting molecule into a final product.

Catabolic Pathways

Metabolic pathways that break down complex molecules into simpler ones, releasing energy in the process.

Cellular Respiration

A major catabolic pathway that breaks down glucose using oxygen to produce energy, carbon dioxide, and water.

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Anabolic Pathways

Metabolic pathways that build complex molecules from simpler ones, requiring energy input.

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Bioenergetics

The study of how energy flows through living organisms.

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Energy

The capacity to cause change.

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Work

The ability to move matter against opposing forces, such as gravity or friction.

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Kinetic Energy

The energy associated with the relative motion of objects. Objects in motion can perform work by imparting motion to other matter.

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Thermal Energy

Kinetic energy associated with the random movement of atoms or molecules.

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Heat

The transfer of thermal energy from one body of matter to another.

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Potential Energy

The energy matter possesses due to its location or structure.

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Chemical Energy

The potential energy available for release in a chemical reaction.

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Catabolic Reaction

The process of breaking down molecules into smaller units, often releasing energy.

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Thermodynamics

The study of energy transformations within a collection of matter.

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System

The matter under study in thermodynamics.

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Surroundings

Everything outside the system in thermodynamics.

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Isolated System

A system that can't exchange energy or matter with its surroundings.

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Open System

A system that can exchange energy and matter with its surroundings.

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First Law of Thermodynamics

The first law of thermodynamics states that energy can be transformed and transferred but never created or destroyed.

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Second Law of Thermodynamics

Every energy transformation increases the entropy of the universe. This means the universe becomes more disordered.

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Spontaneous Process

A process that can happen without external energy input. It increases the entropy of the universe.

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Activation Energy (EA)

The energy needed for a reaction to start, like pushing a ball over a hill to get it rolling downhill.

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Enzyme

A molecule, usually a protein, that speeds up chemical reactions without being consumed.

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Exergonic reaction

A chemical reaction that releases energy, like burning wood.

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Endergonic reaction

A chemical reaction that requires energy input, like building a house.

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Energy Coupling

The use of an exergonic process to drive an endergonic process.

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ATP (Adenosine Triphosphate)

A molecule that stores and releases energy within cells.

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ATP Hydrolysis

The breaking of a phosphate bond in ATP, releasing energy.

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Phosphorylated Intermediate

A molecule that receives a phosphate group from ATP, becoming more reactive.

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ATP Regeneration

The process of adding a phosphate group to ADP to regenerate ATP.

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ATP Cycle

The continuous cycle of ATP being used and then regenerated in a cell.

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Gibbs Free Energy Change (ΔG)

The change in free energy during a reaction, indicating whether it's exergonic or endergonic.

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Free Energy (G)

The portion of a system's energy that can perform work when temperature and pressure are uniform. In living cells, it's the energy available for biological processes.

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Change in Free Energy (∆G)

A change in free energy during a process, calculated as ∆G = ∆H - T∆S, where ∆H is enthalpy change, ∆S is entropy change, and T is absolute temperature.

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Equilibrium

A state where a system is at maximum stability. In a chemical reaction, the rates of forward and backward reactions are equal, meaning no net change in concentrations.

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Metabolic Disequilibrium

A state of disequilibrium where the system is not at maximum stability. It can perform work as it moves towards equilibrium.

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Free Energy (G) as a Measure of Work

The capacity of a system to perform work. In a chemical reaction, it is the maximum amount of work the reaction can perform.

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Catabolic Process

The process of breaking down molecules into smaller components, releasing energy in the form of ATP. Often referred to as 'catabolism'.

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Anabolic Process

The process of building complex molecules from smaller ones, requiring energy input. Often referred to as 'anabolism'.

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Photosynthesis

The process of converting light energy into chemical energy, synthesizing glucose from carbon dioxide and water. It is an endergonic reaction.

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Transition State

The unstable state of reactants when they have enough energy for bonds to break. It's like a chemical 'mountain peak' before the reaction happens.

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Substrate

The reactant that an enzyme binds to and acts upon. It's like the 'key' for an enzyme's 'lock'.

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Active Site

The specific region on an enzyme where the substrate binds and the catalytic action occurs. It's like the 'lock' for the enzyme's 'key'.

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Induced Fit

The change in shape of an enzyme's active site upon binding to a substrate. It's like a glove molding to the shape of a hand.

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Enzyme Action

Enzymes speed up reactions by lowering the activation energy needed for the reaction to occur, but they don't change the overall energy change (ΔG). It's like providing a ramp to push a boulder up a hill.

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Enzyme Saturation

The rate of a reaction catalyzed by a specific amount of enzyme increases as substrate concentration increases, up to a point where all active sites are occupied. It's like a restaurant with limited tables, eventually reaching full capacity.

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Enzyme Specificity

Enzymes are highly specific, each acting on only one or a few substrates. It's like a 'lock and key' model where each key (substrate) only fits a specific lock (enzyme).

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Enzyme Reversibility

Enzymes can catalyze reactions in both forward and reverse directions, depending on the relative concentrations of reactants and products. It's like a swing set where the swing moves both ways, depending on which side is heavier.

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Enzyme Mechanism: Bringing Reactants Together

Enzymes bring reactants together in the correct orientation to facilitate the reaction. It's like bringing together two puzzle pieces that fit perfectly.

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Enzyme Mechanism: Substrate Strain

Enzymes can stretch or strain substrate molecules, destabilizing bonds and making them easier to break. It's like stretching a rubber band before it snaps.

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Enzyme Mechanism: Microenvironment

Enzymes can create a specific microenvironment at the active site, such as altering pH, to facilitate the reaction. It's like creating a 'special' environment for a specific task.

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Increase Enzyme Productivity

To increase product production when the enzyme is saturated, add more enzyme molecules.

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Temperature's Impact on Reaction Rate

Temperature affects how fast a reaction occurs, but too much heat can denature the enzyme.

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Optimal Temperature

Each enzyme works best at a specific temperature, called its optimal temperature.

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pH's Impact on Enzyme Activity

pH affects enzyme activity, with optimal pH ranging from 6-8 for most enzymes.

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Cofactors

Many enzymes require non-protein helpers called cofactors for activity.

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Inorganic Cofactors

Inorganic cofactors are ions like zinc, iron, and copper.

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Enzyme Inhibition

Inhibitors can block the active site, preventing enzymes from catalyzing reactions.

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Irreversible Inhibition

Inhibitors that bind irreversibly to enzymes cause permanent inhibition.

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Reversible Inhibition

Inhibitors that bind reversibly to enzymes cause temporary inhibition, which can be overcome by increasing substrate concentration.

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Competitive Inhibition

Competitive inhibitors resemble the substrate and compete for the active site.

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Noncompetitive Inhibition

Noncompetitive inhibitors bind to a different part of the enzyme, changing its shape and making it less effective.

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Allosteric Regulation

Allosteric regulation occurs when a regulatory molecule binds to a site other than the active site, affecting the enzyme's activity.

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Enzyme Diversity

Mutations in genes can lead to changes in amino acids, which can alter enzyme function and create new enzyme activities.

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Aerobic Respiration

A process that breaks down food molecules to release energy, primarily in the form of ATP, using oxygen.

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Oxidation

The loss of electrons from a substance.

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Reduction

The gain of electrons by a substance.

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Redox Reaction

A chemical reaction that involves the transfer of electrons from one molecule to another. It often involves both oxidation and reduction.

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Reducing Agent

A molecule that acts as an electron donor in a redox reaction.

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Oxidizing Agent

A molecule that acts as an electron acceptor in a redox reaction.

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NAD+

A coenzyme that carries electrons during cellular respiration.

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Electron Transport Chain

A series of membrane-bound proteins that transfer electrons during cellular respiration.

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Anaerobic Respiration

A type of respiration that occurs in the absence of oxygen, using other molecules as electron acceptors.

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Glucose

A molecule that is broken down during cellular respiration to release energy.

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Hydrogen Atom Transfer

The transfer of electrons with a proton, forming a hydrogen atom.

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Cooperativity

A type of allosteric regulation where the binding of a substrate molecule to one active site of a multi-subunit enzyme triggers a shape change in all the subunits, increasing the affinity for the substrate at other active sites.

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Regulatory Site

The site on an allosteric enzyme where the allosteric regulator binds.

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Feedback Inhibition

A form of allosteric regulation where the final product of a metabolic pathway inhibits an earlier step in the same pathway, serving as a negative feedback loop.

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Inhibitory Binding

In feedback inhibition, the final product of a metabolic pathway binds to an early enzyme in the pathway, inhibiting its activity, thereby regulating the production of the product.

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Glycolysis

The breakdown of glucose to pyruvate, a key stage in cellular respiration, occurring in the cytoplasm.

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Citric Acid Cycle

A metabolic pathway that recycles acetyl groups (from pyruvate) to generate ATP and electron carriers, occurring in the mitochondria.

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Oxidative Phosphorylation

The process of using the proton gradient across the mitochondrial membrane to produce ATP, the primary source of energy for cells.

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Fermentation

A process that occurs in the absence of oxygen, generating energy from glucose through pyruvate reduction and fermentation.

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Electron Transfer

The process of transferring electrons between molecules, releasing energy and powering metabolic reactions.

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ATP yield

The amount of ATP generated from one glucose molecule during cellular respiration.

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Electron shuttle

A shuttle system responsible for transporting electrons from the cytosol into the mitochondria.

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Alcohol fermentation

A process where pyruvate is converted to ethanol in two steps.

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Lactic acid fermentation

A process where pyruvate is reduced directly to lactate.

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Acetaldehyde reduction

The process of reducing pyruvate to ethanol.

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Uncoupling protein

A channel protein in inner mitochondrial membrane that allows protons to pass through without generating ATP.

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Brown fat

A type of fat tissue rich in mitochondria that generates heat without ATP production.

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Oxygen

The final electron acceptor in aerobic respiration.

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Activation energy

The energy required to start a chemical reaction.

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Pyruvate Oxidation

The process by which pyruvate is oxidized to acetyl CoA, generating NADH and CO2. It links glycolysis to the citric acid cycle.

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Acetyl CoA

A high-energy molecule that carries two carbon units (acetyl group), produced during pyruvate oxidation and feeds into the citric acid cycle.

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Pyruvate Dehydrogenase Complex

A multienzyme complex that catalyzes the conversion of pyruvate to acetyl CoA.

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Cristae

The folded inner membrane of the mitochondrion, where the electron transport chain and ATP synthase are located.

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Prosthetic Groups

Nonprotein components that assist enzymes in catalysis, often containing metal ions or organic molecules.

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Ubiquinone (Q or CoQ)

A molecule that accepts electrons from the electron transport chain and pumps protons (H+) across the inner mitochondrial membrane, creating a proton gradient.

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ATP Synthase

An enzyme that uses energy from the proton gradient across the inner mitochondrial membrane to synthesize ATP.

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GTP (Guanosine Triphosphate)

A molecule that is used as an energy carrier in many cellular processes. It can be directly hydrolyzed to release energy.

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What is NAD+

A molecule that acts as an electron carrier in cellular respiration. NAD+ can easily switch between an oxidized state (NAD+) and a reduced state (NADH), functioning as a shuttle for electrons.

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How does NAD+ act as an oxidizing agent?

NAD+ acts as an oxidizing agent by accepting electrons from glucose, causing glucose to be oxidized (losing electrons).

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How are electrons extracted from glucose?

During energy production, dehydrogenase enzymes strip electrons from glucose, creating NADH.

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What does NADH represent?

NADH represents stored chemical energy from the breakdown of glucose. This energy is released when NADH donates electrons to the electron transport chain.

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What is the Electron Transport Chain?

The Electron Transport Chain (ETC) is a series of molecules (mostly proteins) embedded in the inner membrane of mitochondria that transfer electrons in a stepwise manner.

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How do electrons move through the Electron Transport Chain?

Electrons from NADH are passed down the Electron Transport Chain to increasingly electronegative molecules, finally reaching oxygen, which is the most electronegative recipient.

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How is energy generated in the Electron Transport Chain?

The energy released by electron transport is used to pump protons across the mitochondrial membrane, creating a proton gradient.

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How is ATP produced using the proton gradient?

The proton gradient created by the Electron Transport Chain is used by ATP synthase to produce ATP.

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What are the three main stages of cellular respiration?

Cellular respiration occurs in three main stages: glycolysis, the citric acid cycle, and oxidative phosphorylation (Electron transport chain and chemiosmosis).

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What happens during glycolysis?

Glycolysis occurs in the cytoplasm and breaks down glucose into two molecules of pyruvate.

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What happens during the citric acid cycle?

The citric acid cycle occurs in the mitochondria and completely oxidizes pyruvate to carbon dioxide, generating ATP and electron carriers (NADH and FADH2).

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What is oxidative phosphorylation?

Oxidative phosphorylation is the final step in cellular respiration, where most ATP is generated. It involves the Electron Transport Chain and chemiosmosis.

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What is substrate-level phosphorylation?

Substrate-level phosphorylation is a direct transfer of a phosphate group from a substrate molecule to ADP, forming ATP.

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Why is cellular respiration efficient?

Cellular respiration breaks down glucose in small, controlled steps to generate ATP, which is a more manageable form of energy for the cell.

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What is the role of ubiquinone in cellular respiration?

Ubiquinone is a mobile electron carrier within the mitochondrial membrane, shuttling electrons between protein complexes. Its movement allows for electron transport and energy release within cellular respiration.

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Describe the role of cytochromes in the electron transport chain.

Cytochromes are proteins containing heme groups with iron atoms that accept and donate electrons. They are essential for the electron transport chain, facilitating electron flow from lower to higher energy levels.

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What is the role of cytochrome a3 in the electron transport chain?

Cytochrome a3, the final cytochrome in the chain, passes electrons to oxygen, which has a high electronegativity. This generates water, completing the process of cellular respiration.

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How does the electron transport chain contribute to ATP synthesis?

Electron transport chain generates a proton gradient across the inner mitochondrial membrane. This gradient is used by ATP synthase to power ATP synthesis.

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What is the function of ATP synthase?

ATP synthase is a protein complex in the mitochondrial cristae that uses the proton gradient generated by the electron transport chain to produce ATP from ADP and inorganic phosphate.

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Explain chemiosmosis and its role in cellular respiration.

The process of ATP synthase using the energy of a proton gradient to produce ATP is known as chemiosmosis. The energy from the gradient is used to drive the phosphorylation of ADP to ATP.

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How is the proton gradient established in mitochondria?

The proton gradient is generated by the electron transport chain, where certain electron carriers accept and release protons along with electrons. This movement of protons builds up a gradient across the inner mitochondrial membrane.

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What is the proton-motive force, and how does it relate to ATP synthesis?

The proton-motive force is the energy stored in the proton gradient across the mitochondrial membrane. It drives protons back across the membrane through ATP synthase, which is the only pathway for proton re-entry.

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What is the significance of chemiosmosis in cellular respiration?

Chemiosmosis is a general mechanism used by cells to couple the energy released from the electron transport chain to perform work, such as ATP synthesis. Similar principles are used in the chloroplasts during photosynthesis.

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Summarize the products and energy yield of cellular respiration.

Cellular respiration oxidizes glucose to carbon dioxide, generating ATP through substrate-level phosphorylation and oxidative phosphorylation. The overall process yields a net gain of ATP molecules.

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Explain the coupling of the electron transport chain and ATP synthesis.

The electron transport chain generates a proton gradient by pumping protons across the inner mitochondrial membrane. The proton-motive force is used by ATP synthase to drive ATP synthesis.

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Why is it challenging to determine the exact number of ATP molecules generated per glucose in cellular respiration?

The ratio of NADH to ATP produced is not a simple whole number because the energy transfer is not perfectly efficient and is influenced by factors such as the membrane's permeability and the proton gradient.

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What is the central role of the electron transport chain in cellular respiration?

Electron transport chain generates a proton gradient by pumping protons across the inner mitochondrial membrane. This gradient is used by ATP synthase to generate ATP, making it a key process connecting electron flow to ATP synthesis.

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How do prokaryotes use the proton-motive force?

Prokaryotes generate a proton gradient across their plasma membrane, using the proton-motive force to drive not only ATP synthesis, but also other processes like nutrient transport and flagellar rotation.

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Describe the mechanism of proton pumping in the electron transport chain.

The electron transport chain in mitochondria uses the energy released from the movement of electrons to pump protons against their concentration gradient. This proton gradient powers ATP synthesis by ATP synthase.

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Lactate

A molecule produced during lactic acid fermentation. It was initially believed to cause muscle fatigue, but recent research suggests potassium ions are more likely responsible for this.

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Lactate Conversion

The process that converts lactate back into pyruvate. This occurs in the liver, allowing the body to re-use energy from lactate.

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Obligate Anaerobe

An organism that can only generate energy through anaerobic respiration or fermentation. It cannot survive in the presence of oxygen.

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Facultative Anaerobe

An organism that can use either aerobic respiration or fermentation to generate energy. It can switch between these modes depending on the availability of oxygen.

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Study Notes

Metabolism Overview

  • Thousands of reactions occur within cells, including assembling polymers from small molecules, hydrolyzing polymers, and exporting chemical products.
  • Cellular respiration extracts energy from fuels to power various cellular processes.
  • Metabolism is complex, efficient, coordinated, and responds quickly to changes.

Metabolic Pathways

  • Metabolism is the sum of all chemical reactions in an organism, emerging from molecular interactions within the cell.
  • Metabolic pathways consist of a chain of reactions, each catalyzed by a specific enzyme.
  • Catabolic pathways break down complex molecules, releasing energy (e.g., cellular respiration).
  • Anabolic pathways build complex molecules from simpler ones, consuming energy (e.g., protein synthesis).

Energy Transformations

  • Energy is the capacity to cause change.
  • Kinetic energy is energy of motion (e.g., thermal energy, light).
  • Potential energy is stored energy (e.g., chemical energy).
  • Chemical energy is released in chemical reactions (e.g., catabolism).
  • Energy transformations follow the laws of thermodynamics.

Thermodynamics

  • An isolated system cannot exchange energy or matter with its surroundings (e.g., liquid in a thermos).
  • An open system can exchange energy and matter (e.g., organisms).
  • The first law of thermodynamics states that energy is conserved.
  • The second law of thermodynamics states that every energy transfer or transformation increases the entropy of the universe.
  • Entropy is a measure of disorder.
  • Spontaneous processes increase the entropy of the universe.

Free Energy and Chemical Reactions

  • Free energy (G) is the portion of a system's energy that can perform work.

  • ∆G is the change in free energy, calculated as ∆G = ∆H - T∆S.

  • ∆G must be negative (∆G < 0) for a spontaneous process.

  • Exergonic reactions release free energy (∆G < 0).

  • Endergonic reactions absorb free energy (∆G > 0).

  • Reactions at equilibrium have a ∆G = 0.

  • Cells maintain metabolic disequilibrium to avoid equilibrium and continue working.

ATP and Cellular Work

  • ATP (adenosine triphosphate)mediates most energy coupling in cells.

  • ATP hydrolysis releases energy (∆G = -7.3 kcal/mol).

  • Hydrolysis of ATP results in a phosphorylated intermediate, making the recipient molecule more reactive.

  • The hydrolysis of ATP is coupled to endergonic processes.

  • ATP is a renewable resource, regenerated by ATP synthase. Catabolism (respiration) supplies the energy to regenerate ATP.

Enzymes and Catalysis

  • Enzymes act as catalysts, speeding up reactions without being consumed.

  • Enzymes lower the activation energy (EA), allowing reactions to occur at normal temperatures.

  • Enzymes are substrate-specific, due to the active site's three-dimensional shape.

  • Induced fit describes the enzyme's shape change to accommodate the substrate.

  • Cofactors (inorganic & nonprotein) and coenzymes (organic & protein) aid enzyme activity.

  • The rate of enzyme action depends on substrate concentration and the temperature & pH optima of the enzyme.

  • Inhibitors can bind to enzymes reversibly or irreversibly, altering their function (competitive or noncompetitive).

Metabolic Regulation

  • Allosteric regulation describes an enzyme's activity alteration by a molecule binding to a non-active site.
  • Feedback inhibition regulates a metabolic pathway by the pathway's final product inhibiting an earlier step.
  • Enzyme localization within the cell helps organize metabolic pathways.

Cellular Respiration

  • Cellular respiration is a catabolic metabolic pathway. It harvests energy from organic molecules, using oxygen.
  • Cellular respiration has three main stages: glycolysis, citric acid cycle, and oxidative phosphorylation.
  • Redox reactions transfer electrons and release energy used in ATP synthesis.

Glycolysis

  • Glycolysis breaks down glucose, a six-carbon molecule, into two three-carbon molecules of pyruvate, producing 2 ATP and 2 NADH.
  • Glycolysis occurs in the cytosol and is an anaerobic process.

Pyruvate Oxidation

  • Pyruvate is oxidized to acetyl CoA, releasing CO2 and transferring electrons to NAD+, producing NADH.

Citric Acid Cycle

  • The citric acid cycle further oxidizes acetyl CoA, releasing CO2, producing 1 ATP per turn, NADH, and FADH2 by substrate-level phosphorylation.

Oxidative Phosphorylation

  • Electron transport chain transfers electrons from NADH and FADH2 to oxygen, creating a proton gradient.
  • Chemiosmosis uses the proton gradient to drive ATP synthesis.
  • ATP synthase is a protein that synthesizes ATP using the H+ gradient (proton-motive force).
  • Oxidative phosphorylation produces most of the ATP in cellular respiration.

Fermentation

  • Fermentation is an anaerobic alternative to respiration, regenerating NAD+ (by reducing pyruvate) for glycolysis, producing a small amount of ATP.
  • Examples are alcohol fermentation (ethanol) and lactic acid fermentation (lactate).

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Description

Test your knowledge on the fundamental concepts of metabolism and energy transfer within living organisms. This quiz covers key terms, pathways, and the laws of thermodynamics that govern biological energy systems. Challenge yourself to understand how energy flows and the role of enzymes in metabolic reactions.

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