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AP Bio Exam: Unit 3

AP Exam

QuestionAnswer
What is an enzyme? Biological catalyst (usually protein) that speeds up reactions by lowering activation energy.
What is the structure of an enzyme? Complex 3D protein with a specific active site shape determined by amino acid sequence.
How does the structure of an enzyme contribute to the regulation of biological processes? Specificity allows enzymes to regulate specific metabolic pathways precisely.
What is the function of an enzyme? Lowers activation energy to increase reaction rate without being consumed.
How does the function of an enzyme contribute to the regulation of biological processes? Controls reaction rates, determining when cellular processes occur.
How does the enzyme complete this function? Binds substrates at active site, stabilizing transition state to facilitate reaction.
What is the monomer that makes up an enzyme? Amino acids.
How does an enzyme affect the rate of a reaction? Increases rate by lowering activation energy required for reaction to proceed.
What is an enzyme-catalyzed reaction? Reaction accelerated by enzyme binding to substrate(s) to lower activation energy.
How is the activation energy of an enzyme-catalyzed reaction and an uncatalyzed reaction different? Catalyzed reaction has lower activation energy than uncatalyzed reaction.
How is the change in free energy of an enzyme-catalyzed reaction and an uncatalyzed reaction different? No difference; enzymes do not change the net free energy change (ΔG).
How is the reaction rate of an enzyme-catalyzed reaction and an uncatalyzed reaction different? Catalyzed reaction occurs much faster due to lower activation energy.
True or False? Enzymes affect the Gibbs Free Energy of a chemical reaction. False; enzymes lower activation energy but do not change ΔG.
How does a substrate bind to an enzyme? Substrate binds to active site via weak interactions (hydrogen bonds, ionic).
What is this called when the enzyme and substrate are bonded together? Enzyme-substrate complex.
What happens after the substrate binds to the enzyme? Enzyme facilitates conversion of substrate to product; products are released.
How does the shape and charge of a substrate affect the binding to the active site of the enzyme? Substrate must fit chemically and spatially into active site for binding.
Identify two conditions that affect the structure of an enzyme. Temperature and pH.
What happens to the structure of the enzyme in these conditions? Extreme conditions can denature enzyme, altering its active site shape.
How does a change in structure affect the function of an enzyme? Altered active site reduces substrate binding, decreasing or stopping function.
Predict the three different possible outcomes when there is a change in structure of an enzyme. Increased activity, decreased activity, or complete loss of function.
What happens to the pH when the concentration of hydrogen ions increases? pH decreases (more acidic).
What happens to the pH when the concentration of hydrogen ions decreases? pH increases (more basic).
What happens to an enzyme when the pH increases? Enzyme may denature if pH moves outside optimal range.
What happens to an enzyme when the pH decreases? Enzyme may denature if pH moves outside optimal range.
How does the temperature affect the kinetic energy of the molecules? Higher temperature increases kinetic energy; lower temperature decreases it.
What happens to an enzyme when the temperature increases? Rate increases up to optimal point; excessive heat causes denaturation.
How is the frequency of collisions affected by decreased temperature? Decreased temperature reduces molecular speed, leading to fewer collisions.
How does temperature affect the rate of a reaction? Higher temperatures increase reaction rates by increasing collision frequency and energy.
Describe what happens to an enzyme if the optimal temperature is surpassed. The enzyme denatures, losing its shape and function.
What is a competitive inhibitor? A molecule that binds to the active site, blocking substrate binding.
How can a researcher overcome a competitive inhibitor? Increase substrate concentration to outcompete the inhibitor.
Describe the binding site for a competitive inhibitor. The active site of the enzyme.
What is a noncompetitive inhibitor? A molecule that binds to an allosteric site, changing enzyme shape.
Describe the binding site for a noncompetitive inhibitor. An allosteric site away from the active site.
How does an inhibitor affect reaction rate? It decreases the rate of reaction by slowing enzyme activity.
How are cellular processes powered? By energy released from catabolic reactions like cellular respiration.
What is the first law of thermodynamics? Energy cannot be created or destroyed, only transferred.
What is the second law of thermodynamics? Energy transformations increase entropy (disorder) in the universe.
How is order (entropy) maintained in a system? By constant input of energy to maintain organization.
What is an exergonic reaction? A reaction that releases energy; products have less free energy than reactants.
What is an endergonic reaction? A reaction that absorbs energy; products have more free energy than reactants.
Describe the process of energy coupling. Using energy from an exergonic reaction to drive an endergonic one.
Explain why energy coupling is needed within the cell. To power essential anabolic processes that require energy input.
What happens if there is a decrease in available energy or a loss of order? Cellular processes fail and the system becomes more disordered.
What is a metabolic pathway? A series of enzyme-catalyzed reactions where the product of one is the substrate for the next.
How do catabolic and anabolic pathways differ? Catabolic breaks down molecules for energy; anabolic builds molecules using energy.
In a metabolic pathway, how does the product of one step compare to the reactant of the next step? The product of one step becomes the reactant for the next.
Using the given pathway Tryptophan --(Enzyme Trp-T)-> I3PA ---(Enzyme YUC)--> IAA, how is the pathway affected by a decrease in Tryptophan? Less substrate available reduces I3PA and IAA production.
Using the given pathway Tryptophan --(Enzyme Trp-T)-> I3PA ---(Enzyme YUC)--> IAA, how is the pathway affected by a decrease in Enzyme Trp-T? Accumulation of Tryptophan and reduction of I3PA and IAA.
Using the given pathway Tryptophan --(Enzyme Trp-T)-> I3PA ---(Enzyme YUC)--> IAA, how is the pathway affected by a decrease in I3PA? Reduction of IAA production due to lack of substrate.
Using the given pathway Tryptophan --(Enzyme Trp-T)-> I3PA ---(Enzyme YUC)--> IAA, how is the pathway affected by a decrease in Enzyme YUC? Accumulation of I3PA and reduction of IAA.
Using the given pathway Tryptophan --(Enzyme Trp-T)-> I3PA ---(Enzyme YUC)--> IAA, how is the pathway affected by a decrease in IAA? No effect on upstream steps; feedback inhibition may be reduced.
True or False? All organisms perform glycolysis. True.
Explain how glycolysis has been conserved across all domains. It is an ancient pathway found in the last universal common ancestor.
Justify the claim that glycolysis first occurred in the common ancestor for all living organisms. Its presence in all three domains suggests it evolved early in life's history.
Explain how oxidative phosphorylation is performed in archaea. Using a unique membrane and electron transport chain adapted to extreme environments.
Explain how oxidative phosphorylation is performed in bacteria. Using the plasma membrane to generate a proton gradient.
Explain how oxidative phosphorylation is performed in eukaryotes. Using the inner mitochondrial membrane to generate ATP.
What is photosynthesis? The process by which plants, algae, and some bacteria convert light energy into chemical energy.
Identify the reactants and products for photosynthesis. Reactants: CO2 and H2O; Products: Glucose and O2.
Describe the process of photosynthesis. Light energy converts water and CO2 into glucose and oxygen using chloroplasts.
What types of organisms are able to perform photosynthesis? Plants, algae, and cyanobacteria.
Identify TWO examples of photosynthetic organisms. Oak trees and kelp.
What organism first evolved photosynthesis? Cyanobacteria.
Identify one piece of evidence that supports oxygenation to atmosphere from cyanobacteria. Banded iron formations showing oxidation of ocean iron.
Describe how the prokaryotic photosynthetic pathway has led to eukaryotic photosynthesis. Endosymbiosis of a cyanobacterium became the chloroplast.
What is the structure and function of a chloroplast? Double membrane with thylakoids; site of photosynthesis.
How does the structure of the chloroplast aid in the function? Thylakoids increase surface area for light absorption.
What is the stroma? The fluid-filled space outside the thylakoids in the chloroplast.
Describe the process that takes place in the stroma. The Calvin Cycle fixes CO2 into sugar.
What is the thylakoid membrane? The membrane surrounding the thylakoid lumen containing photosystems.
Describe the process that takes place in the thylakoid membrane. Light reactions generate ATP and NADPH.
What is chlorophyll? A pigment that absorbs light energy for photosynthesis.
Where would you find chlorophyll in the chloroplast? Embedded in the thylakoid membranes.
How is the thylakoid organized to facilitate ATP and NADPH synthesis? Stacked into grana to organize electron transport components.
Describe the light reactions. Light energy splits water, producing ATP, NADPH, and O2.
Describe the dark reactions (aka the Calvin Cycle. Uses ATP and NADPH to fix CO2 into glucose.
How is energy coupled between the light reactions and the Calvin cycle? ATP and NADPH from light reactions power sugar synthesis.
What is the electron transport chain? A series of proteins that transfer electrons to create a proton gradient.
Where do the electron transport chain reactions take place? Thylakoid membrane in photosynthesis; inner mitochondrial membrane in respiration.
Describe the process of the electron transport chain in photosynthesis. Electrons move through photosystems to pump protons into the thylakoid space.
How does the electron transport chain in cellular respiration compare to the electron transport chain in photosynthesis? Both create proton gradients, but respiration uses food energy while photosynthesis uses light.
How does the electron transport chain in prokaryotic plasma membranes compare to the electron transport chain in photosynthesis? Both occur across membranes to generate gradients, but differ in energy source and location.
How is NADPH formed during the light reactions? Electrons from photosystem I reduce NADP+ to NADPH.
What are the light reactions? The first stage of photosynthesis converting light to chemical energy.
Where do the light reactions take place? In the thylakoid membranes of the chloroplast.
Describe the process of the light reactions in photosynthesis. Light excites electrons, which move through an ETC to generate ATP and NADPH.
Describe the pathway of an electron through the light reactions with linear electron flow? From H2O to PSII to PSI to NADPH.
Describe the pathway of an electron through the light reactions with cyclic electron flow? From PSI back to the cytochrome complex to generate only ATP.
What is photolysis? The splitting of water molecules by light energy.
Identify the location where photolysis takes place. The thylakoid lumen side of photosystem II.
Describe the process of photolysis. Light energy splits water into electrons, protons, and oxygen.
Justify the claim that photosynthesis would halt if photolysis was inhibited. No electrons would be available to replace those lost from photosystem II.
Describe the structure of the thylakoid membrane in chloroplasts. Contains photosystems, electron transport chains, and ATP synthase.
Diagram the thylakoid membrane including and labeling photosystem I and II, the electron transport system, and the final electron acceptor. (Diagram required: PSII, ETC, PSI, NADP+ reductase).
Describe the electron transport chain in photosynthesis. Series of proteins transferring electrons to pump protons.
Explain how the proton gradient is generated in photosynthesis. Protons are pumped into the thylakoid space as electrons move down the ETC.
Identify which side of the membrane would have a lower pH. The thylakoid lumen.
Explain why this side of the membrane would have a lower pH. High concentration of H+ ions accumulates there.
Describe how the proton gradient in a chloroplast facilitates ATP synthesis. H+ flows back through ATP synthase, driving ATP production.
Describe chemiosmosis. The movement of protons across a membrane down their gradient to drive ATP synthesis.
Describe photophosphorylation. Synthesis of ATP using light energy to create a proton gradient.
This is energy coupling, identify the exergonic reaction and the endergonic reaction. Exergonic: Electron flow; Endergonic: ATP synthesis.
What is the product of photophosphorylation? ATP.
Describe how the light reactions and the Calvin cycle are connected. Light reactions produce ATP and NADPH used in the Calvin Cycle.
Describe the light reactions. Convert light energy to chemical energy (ATP/NADPH).
Describe the Calvin cycle. Fixes CO2 into organic molecules using ATP and NADPH.
What is cellular respiration? The process of breaking down glucose to produce ATP.
What is fermentation? An anaerobic process that allows glycolysis to continue by regenerating NAD+.
What are the three steps involved in cellular respiration? Glycolysis, Krebs Cycle, and Oxidative Phosphorylation.
What is the function of each step in cellular respiration? Glycolysis breaks glucose; Krebs releases energy; OxPhos produces most ATP.
True or False: Each step in cellular respiration results in energy being captured and stored as ATP. False; some energy is lost as heat.
Which macromolecules can be used by the cell to capture energy? Carbohydrates, lipids, and proteins.
What is the electron transport chain? A series of protein complexes that transfer electrons to create a proton gradient.
Where is the electron transport chain in a mitochondrion? Embedded in the inner mitochondrial membrane.
Where is the electron transport chain in a prokaryote? Embedded in the plasma membrane.
Describe how the electrons are brought to the electron transport chain. NADH and FADH2 carry electrons from earlier stages.
What occurs as electrons are transferred from one cytochrome to the next in the electron transport chain? Protons are pumped across the membrane.
What is the final electron acceptor in the electron transport chain during aerobic respiration? Oxygen.
Identify another molecule that can be used as a final electron acceptor in anaerobic respiration. Nitrate or sulfate.
Describe the proton movement as the electron moves through the electron transport chain. Protons move from the matrix to the intermembrane space.
Which side of the membrane will have a higher concentration of hydrogen ions? The intermembrane space.
How does this affect the pH of that region? It lowers the pH (more acidic).
Explain why the cristae is highly folded. To increase surface area for more electron transport chains and ATP production.
Describe chemiosmosis. The diffusion of protons through ATP synthase to drive ATP synthesis.
What is the function of ATP Synthase? Uses the proton gradient to phosphorylate ADP into ATP.
Describe oxidative phosphorylation. The production of ATP using energy derived from the electron transport chain.
What is decoupling oxidative phosphorylation? Disrupting the proton gradient so energy is released as heat instead of ATP.
How does it generate heat? Energy from the ETC is dissipated as thermal energy.
How is this different than the oxidative phosphorylation? It produces heat instead of ATP.
What is glycolysis? The breakdown of glucose into pyruvate in the cytoplasm.
Where does glycolysis take place? In the cytoplasm.
Identify the reactants and products of glycolysis. Reactants: Glucose, 2 ATP, 2 NAD+; Products: Pyruvate, 4 ATP, 2 NADH.
True or False: Glycolysis requires oxygen. False.
How is ATP synthesized in glycolysis? Substrate-level phosphorylation transfers phosphate to ADP.
What is the Krebs Cycle? A series of reactions that oxidize acetyl-CoA to produce electron carriers.
Where does the Krebs Cycle take place? In the mitochondrial matrix.
Identify the reactants and products of the Krebs cycle. Reactants: Acetyl-CoA; Products: CO2, ATP, NADH, FADH2.
True or False: The Krebs Cycle requires oxygen. False, but it stops without oxygen due to lack of NAD+.
How is ATP synthesized in the Krebs Cycle? Substrate-level phosphorylation.
What is oxidation? The loss of electrons or hydrogen atoms.
What is reduction? The gain of electrons or hydrogen atoms.
What molecules are reduced in glycolysis and the Krebs cycle? NAD+ and FAD are reduced to NADH and FADH2.
Where do these reduced molecules go to be oxidized? The electron transport chain.
What occurs as electrons are transferred from one cytochrome to the next in the electron transport chain? Energy is used to pump protons across the membrane.
What is the function of the electrochemical gradient formed during the electron transport chain? To drive ATP synthesis via chemiosmosis.
Describe the process of fermentation. Anaerobic conversion of pyruvate to lactate or alcohol to regenerate NAD+.
Where does the fermentation take place? In the cytoplasm.
Identify the reactants and products of the fermentation. Reactants: Pyruvate and NADH; Products: NAD+ and fermentation products like lactate or ethanol.
TRUE or FALSE: ATP is synthesized during fermentation. False; fermentation regenerates NAD+ but does not produce additional ATP.
What process precedes fermentation to aid in ATP synthesis? Glycolysis produces the net ATP and pyruvate used before fermentation.
Why is it more favorable for a cell to undergo aerobic respiration instead of fermentation? Aerobic respiration produces significantly more ATP (approx. 30-32) per glucose than fermentation (2).
Created by: chianti
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