Biochem Unit 2

How many reduced cofactors (NADH or FADH2) are formed in this reaction? (review Quiz 4 Q4)

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17. Which of the following could be converted into the most molecules of acetyl-CoA? A) 1 mole of a 6 carbon fatty acid B) 1 mole of the 6 carbon sugar glucose C) 1 mole of the 6 carbon sugar fructose 1,6 bisphosphate D) 2 moles of the 3 carbon compound pyruvate E) All of the choices have the same number of carbons and would therefore be converted to the same number of acetyl-CoA's

A) 1 mole of a 6 carbon fatty acid.

4. The reaction F↔G has a free energy change of (ΔG°') of -6 kJ/mol under standard conditions (i.e. standard conditions are starting conditions of 1M of F and G, and then ΔG°' is by convention for the F→G direction). What relative amounts of F & G at the START of the reaction would result in a free energy change (ΔG°') of +6 kj/mol as the reaction proceeds to equilibrium? A) 1F to 100G B) 1F to 10G C) 1F to 1G D) 10F to 1G E) 6G to 1F

A) 1F to 100G

31. In the light reactions of photosynthesis, light energy is used to: A) Dissociate water into O2, protons and high energy electrons. B) dissipate a proton gradient. C) oxidize NADPH D) Convert acetyl-CoA into glucose

A) Dissociate water into O2, protons and high energy electrons.

27) Electrons transferred to the electron transport chain from FADH2 (these electrons come from the oxidation of succinate or fatty acids) make fewer ATPs than electrons that are transferred to Complex I from NADH. Why? A) FADH2 enters the electron transport chain at complex II, which does not pump protons. B) FADH2 is made during the TCA cycle. C) Electrons from FADH2 bypass complex IV D) B + C E) A + C

A) FADH2 enters the electron transport chain at complex II, which does not pump protons.

11. Enzymes accelerate reactions by: A) Lowering the activation energy required for the reaction. B) Changing Keq to favor the formation of productions. C) Preventing the reverse reaction so that the net forward reaction is greater than that for the uncatalyzed reaction D) All of the above

A) Lowering the activation energy required for the reaction.

21. The conversion of arginine to ornithine is a step in the synthesis of: A) urea B) glutamic acid C) carnitine D) lactate

A) Urea

How many net ATP are formed in glycolysis per glucose molecule? A. 2 B. 3 C. 4 D. 1

A. 2

How many reduced bonds does acetate have? In other words, how many reduced cofactors are formed when acetate is fully oxidized in the citric acid cycle? A. 4 B. 2 C. 6 D. 3

A. 4

The following is a review question. Which of the following will allosterically increase the activity of phosphofrutokinase-1? A. AMP B. ATP C. NADH

A. AMP

Where is pyruvate dehydrogenase complex localized? A. Mitochondria B. Cytosol

A. Mitochondria

Which of the following is a product of the pyruvate dehydrogenase complex? A. NADH B. ADP C. FADH2 D. ATP

A. NADH

Reactions that have positive ∆E°' values will proceed to the ______. A. Right B. Left

A. Right

The proton motive force is required to release the ATP that is bound to ATP synthase A. True B. False

A. True

22) The regulation of the enzyme citrate synthase is a control point for the citric acid cycle. Which of the following is true (and metabolically logical) regarding the regulation of citrate synthase? A) ATP and NADH promote enzyme activity B) ATP and NADH inhibit enzyme activity C) ATP and NAD+ promote enzyme activity D) NADH and ADP inhibit enzyme activity

B) ATP and NADH inhibit enzyme activity

8. Consider the short pathway with the following standard free energy changes (ΔG°') for each step: -7.5, +7.5, -0.2, -23 A↔Β ↔C↔D→E If the conversion of D→E is blocked by an enzyme inhibitor, which compound in the pathway will accumulate to the highest levels? A) A B) B C) C D) D E) E

B) B

10. During the fermentation of glucose to ethanol in yeast, pyruvate is converted to ethanol because: A) additional energy can be produced by the oxidation of the NADH that is formed during ethanol production B) NAD+ must be replenished for glycolysis to continue. C) It is necessary to reduce pyruvate before it can be converted to CO2 and H2O in the TCA cycle. D) ethanol is more oxidized than pyruvate.

B) NAD+ must be replenished for glycolysis to continue.

18. Pyruvate dehydrogenase is a large multi-subunit complex that is composed of 3 types of subunits that carry out different steps of the overal reaction. α ketoglutarate dehydrogenase is also a large multi-subunit complex that is composed of 3 types of subunits. The E1 and E2 subunits of both enzymes are very similar and obviously evolutionarily related, and the E3 subunits are identical. How is it possible that these enzyme complexes could have identical E3 subunits? A) The E3 subunits do not participate in catalysis; their role is simply to hold the E1 and E2 subunits together. B) The E3 subunits do not interact with pyruvate or α-ketoglutarate, and the reactions that the E3 subunits catalyze have identical substrates and products in both complexes. C) The E3 subunits play only a regulatory role. D) Pyruvate and α-ketoglutarate are sufficiently similar that the same subunit can use both compounds as substrate.

B) The E3 subunits do not interact with pyruvate or α-ketoglutarate, and the reactions that the E3 subunits catalyze have identical substrates and products in both complexes.

19. Almost all of your energy is derived from: A) The conversion of C-0 and C=O bonds into H2O and CO2 B) The conversion of C-H and C-C bonds into H2O and CO2 C) Glycolysis D) The Urea Cycle E) The conversion of CO2 into H2O

B) The conversion of C-H and C-C bonds into H2O and CO2

1. The combustion (burning) of paper to form releases heat (it is an exothermic reaction) because: A) The free energy change (ΔG) for this reaction is positive. B) The products (CO2 + H2O) have more stable chemical bonds than the reactants. C) The entropy of the products (CO2 + H2O) is less than that of the reactants. D) The carbon atom of is more reduced than most of the carbon atoms in paper.

B) The products (CO2 + H2O) have more stable chemical bonds than the reactants.

30. Which of the following is FALSE regarding ubiquinone? (Ubiquinone is an electron carrier of the mitochondrial electron transport chain; its reduced form is called Ubiquinol.) A) Ubiquinone is soluble in membranes B) Ubiquinol donates electrons to Complex IV C) Ubiquinone accepts electrons from Complex I D) Ubiquinone accepts electrons from Complex II

B) Ubiquinol donates electrons to Complex IV

Which of the following molecules allosterically inhibits phosphofrutokinase (the third enzyme in glycolysis)? Think about what makes metabolic sense. A. ADP B. ATP C. AMP

B. ATP

Water is the only source of electrons for photosynthetic organisms? A. True B. False

B. False

Glutamine synthetase adds NH3 to ____________ to generate glutamine. A. Alpha-ketoglutarate B. Glutamate C. Carbamoyl phosphate D. Alanine

B. Glutamate

Where do the electrons needed to start photosystem II come from? A. O2 B. H2O C. Quinone

B. H2O

Where does the citric acid cycle take place? A. Cytosol B. Mitochondria

B. Mitochondria

Which of the following statements regarding fermentation is CORRECT? A. Fermentation occurs more readily in aerobic conditions (oxygen present) than in anaerobic conditions (oxygen not present). B. The lactate dehydrogenase reaction regenerates NAD+ for glycolysis. C. Glucose consumption is lower in anaerobic conditions (oxygen not present) in comparison to aerobic conditions (oxygen present). D. The enzyme alcohol dehydrogenase regenerates NADH for glycolysis.

B. The lactate dehydrogenase reaction regenerates NAD+ for glycolysis.

Steps 1, 3 and 10 of glycolysis are irreversible. Which of the following statements regarding glycolysis is INCORRECT A. Cellular conditions do not exist that allow for steps 1, 3, and 10 to proceed in the reverse direction B. The standard free energy changes for steps 1, 3, and 10 are large and positive. C. Steps 1, 3, and 10 are catalyzed by kinases.

B. The standard free energy changes for steps 1, 3, and 10 are large and positive.

3. The reaction F↔G has a free energy change of (ΔG°') of -6 kJ/mol under standard conditions (i.e. standard conditions are starting conditions of 1M of F and G, and then ΔG°' is by convention for the F→G direction). What are the relative amounts of F&G when the reaction F↔G reaches equilibrium? A) 10F to 1G B) 1F to 1G C) 1F to 10G D) 1F to 100G E) 6F to

C) 1F to 10G

12. How many steps of the citric acid cycle produce CO2? A) 0 B) 1 C) 2 D) 3 E) 4

C) 2

16. How many cycles β-oxidation are required to completely convert an 18 carbon fatty acid into acetyl-CoA A) 1 B) 7 C) 8 D) 10 E) 18

C) 8

6. Which of the following is true about the preparatory steps of glycolysis? (The preparatory steps are the conversion of glucose to glyceraldehyde-3-phosphate.) A) NAD+ is reduced to NADH. B) A phosphate group (Pi) from fructose-6-phosphate is transferred to ADP to form ATP. C) ATP is consumed (i.e., converted to ADP). D) Pyruvate is converted to lactate

C) ATP is consumed (i.e., converted to ADP).

29. Many years ago, dinitrophenol (DNP) was used as a diet pill to help individuals lose weight. DNP is an uncoupler that dissipates the proton gradient across membranes (such as the mitochondrial inner membrane). DNP is no longer used as a diet pill because several people died while taking DNP to lose weight. Why is DNP effective as a diet pill and why is it dangerous? A) DNP decreases the rate of NADH oxidation and can decrease ATP production B) DNP increases the rate of electron transport and can increase ATP production C) DNP increases the rate of NADH oxidation and can decrease ATP production. D) DNP ensures that the only path for proton flow from the outside to the inside of the inner mitochondrial membrane is through ATP synthase

C) DNP increases the rate of NADH oxidation and can decrease ATP production.

28. Consider the following half reactions and their ΔE0' values (standard conditions). X + 2e- + 2H+ → XH2 ΔE0' = -0.6V X + 2e- + 2H+ → YH2 ΔE0' = -0.1V If 1 mole of X, Y, XH2, and YH2 are mixed in solution the NET reaction that could occur is: (Of course all 4 species will change if a reaction occurs but only 2 of the 4 are listed in each answer. Think about the direction the e- will flow based on ΔE0' values) A) The level of X will decrease and the level of Y will increase B) The level of XH2 will decrease and the level of Y will increase C) The level of X will increase and the level of Y will decrease. D) The level of XH2 will increase and the level of YH2 will decrease.

C) The level of X will increase and the level of Y will decrease.

7. For which of the following compounds is the donation of a phosphate to ADP to form ATP (a substrate-level phosphorylation) an UNFAVORABLE reaction at standard conditions? A) phosphoenolypyruvate B) 1,3 bisphosphoglycerate C) glucose-6-phosphate D) substrate level phosphorylation is not favorable from any of the compounds listed

C) glucose-6-phosphate

20. Which of the following reactions could be catalyzed by an aminotransferase? A) N2 + 3H → 2NH3 B) orinthine + carbamoyl phosphate → citrulline C) glutamate + oxaloacetate → α-ketoglutarate + aspartate D) arginosuccinate → fumarate + arginine

C) glutamate + oxaloacetate → α-ketoglutarate + aspartate

How many molecules of CO2 are formed in the citric acid cycle per acetyl-CoA? A. 0 B. 3 C. 2 D. 4 E. 1

C. 2

How many pyruvate molecules are formed from one molecule of glucose? A. 4 B. 1 C. 2 D. 3

C. 2

What products from the "light" reactions are used in the "dark" reactions? A. ATP B. NADPH C. Both A and B

C. Both A and B

Consider the pyruvate dehydrogenase complex. When is carbon dioxide formed in th pyruvate hydrogenase reaction mechanism? A. E3 reactions B. E2 reactions C. E1 reactions

C. E1 Reactions

Arginine and __________ are formed in the urea cycle when argininosuccinate is split into two molecules. A. Ornithine B. Urea C. Fumarate D. Citrulline

C. Fumarate

What product of the Calvin Cycle is used as a precursor in the synthesis of sucrose or starch? A. Ribulose 5-phosphate B. CO2 C. Gylceraldehyde 3-phosphate

C. Glyceraldehyde 3-phosphate

Which of the following complexes in the electron transport chain does not pump hydrogen ions into the inner membrane space of the mitochondria? A. III B. I C. II D. IV

C. II

Which of the following statements regarding Gibbs free energy is CORRECT? A. If a reaction has a negative actual free energy change (∆G), the standard free energy change (∆G°) has to also be negative B. If a reaction has a large and negative standard free energy change (∆G°), the enzyme "prefers" to form reactants. C. If a reaction has a large and negative standard free energy change (∆G°), product formation will be favored in actual conditions unless the ratio of products to reactants is high enough to drive the reaction in the reverse direction. D. If a reaction has a large and positive actual free energy change (∆G), product formation is favored.

C. If a reaction has a large and negative standard free energy change (∆G°), product formation will be favored in actual conditions unless the ratio of products to reactants is high enough to drive the reaction in the reverse direction.

5. The reaction A→B has a standard free energy change of (ΔG°') of +11 kj/mol. In the cell, the formation of B is coupled to the conversion of C→D. To obtain a net gain in the amoung of B from the coupled reaction under standard conditions, the ΔG°' for C→D must be: A) Between -1 and -11 kJ/mol B) Between +1 and +11 kJ/mol C) Greater than +11 kJ/mol (for example +20 kJ/mol) D) Less than -11 kJ/mol (for example -20 kJ/mol)

D) Less than -11 kJ/mol (for example -20 kJ/mol)

14. The standard free energy (ΔG°') for the following reaction is NEGATIVE (~ -30 kj/mol). malate + 1/2 O2→oxaloacetate + H2O However, the reaction by which malate is converted to oxaloacetate in the citric acid cycle has a positive standard free energy change (ΔG°') of ~ +30 kJ/mol. The reason for the positive STANDARD free energy change in the citric acid cycle is: A) The conversion of malate to oxaloacetate is coupled to ATP breakdown. B) The conversion of malate to oxaloacetate is coupled to ATP synthesis. C) The conversion of malate to oxaloacetate is necessary for the citric acid cycle to proceed. D) The conversion of malate to oxaloacetate is coupled to the reduction of NAD+

D) The conversion of malate to oxaloacetate is coupled to the reduction of NAD+

9. Yeast cells can grow anaerobically (without oxygen) by fermenting glucose to ethanol and can also completely oxidize glucose to CO2 and H2O during aerobic growth. When yeast are grown anaerobically the amount of glucose consumed per amount of growth is much higher than during aerobic growth. This is because: A) during anaerobic growth much of the glucose is used to make starch. B) glycolysis is blocked in aerobic conditions. C) glucose is used inefficiently in the presence of oxygen D) the yield of ATP per glucose is much higher in aerobic than in anaerobic conditions.

D) The yield of ATP per glucose is much higher in aerobic than anaerobic conditions.

2. For the reaction: A + B ↔ C + D, Keq (for the left to right reaction direction) =2x10^2 (i.e., Keq = 200). Which of the following is true? (Note ΔG°' is the free energy change as the reaction proceeds from standard conditions to equilibrium.) A) There is more A + B than C + D at equilibrium, and ΔG°' is positive. B) There is more C + D than A + B at equilibrium, and ΔG°' is positive. C) There is more A + B than C + D at equilibrium, and ΔG°' is negative. D) There is more C + D than A + B at equilibrium, and ΔG°' is negative.

D) There is more C + D than A + B at equilibrium, and ΔG°' is negative.

For every one NADH molecule oxidized at complex I, how many TOTAL hydrogen ions are pumped across all of the complexes from the mitochondrial matrix to the inner membrane space? A. 4 B. 12 C. 1 D. 10

D. 10

Natural uncoupler proteins dissipate the proton gradient. Which of the following is a consequence of uncoupler proteins? A. Increased formation of water from oxygen B. Generation of heat C. Increased beta-oxidation of fatty acids D. All of the above

D. All of the above

Which of the following statements regarding the urea cycle is INCORRECT? A. Nitrogen can be delivered from the muscle via alanine B. One of the nitrogen atoms in urea is donated from aspartate C. One of the nitrogen atoms in urea is donated from glutamate D. All steps of the urea cycle occur in the cytosol.

D. All steps of the urea cycle occur in the cytosol.

Nitrogen enters the liver mitochondria in which of the following molecules? A. Aspartate and carbamoyl phosphate B. Alanine and oxaloacetate C. Fumarate and urea D. Glutamate and glutamine

D. Glutamate and glutamine

Consider the reaction A → B where ∆G° = 25 kJ/mol. Which of the following statements is INCORRECT? A. The formation of B may be favored in physiological conditions if there is enough A to drive the reaction forward. B. The actual free energy (∆G) has to also be 25 kJ/mol C. The Keq is less than 1 D. The formation of A is favored in standard conditions

D. The formation of A is favored in standard conditions

13. How many steps of the citric acid cycles are oxidation reactions? A) 0 B) 1 C) 2 D) 3 E) 4

E) 4

15. Which of the following enzymatic activities would be decreased by thiamine deficiency? A) Fumarase B) Isocitrate dehydrogenase C) Malate dehydrogenase D) Succinate dehydrogenase E) Pyruvate dehydrogenase complex

E) Pyruvate dehydrogenase complex

2,4-Dinitrophenol (DNP) has been banned by the FDA but was previously used in the United States as a diet pill. In the presence of sub-lethal doses of DNP the rate of which of the following processes will increase? A. ATP Production B. Beta-oxidation of fatty acids C. Formation of water D. All of the above E. Only B and C

E. Only B and C (i.e. Beta-oxidation of fatty acids and Formation of water)

32. True or False: The evolution of the ability of organisms to obtain energy from the oxidation of carbon bonds required the presence of (O2) in the atmosphere.

False

True or False: Electron transport chains could not have evolved until 02 became available in the atmosphere.

False

True or False: Oxygen is the only electron acceptor for cellular respiration on our planet today.

False

True or False: The only sources of energy used by organisms currently living on early are reduced carbon or light.

False

____ has the highest affinity for electrons while _____ has the lowest affinity for electrons in the following half-reactions

The equation with the higher E'° (V) value.

33. True or False: RNA molecules were likely to have been the first enzymes in the earliest forms of life (i.e. RNA enzymes were present before protein enzymes).

True

True or False: Life evolved on earth BEFORE there was oxygen (O2) in the atmosphere?

True

True or False: Methane is a more potent greenhouse gas than carbon dioxide

True

True or False: The evolution of photosynthesis caused the extinction of many microbes.

True

True or False: The world's human population strongly correlates with atmospheric concentrations of carbon dioxide.

True

The symbol ∆G° represents ________ while ∆G represents ________.

a standard reference point; actual conditions