Question 1

Which of the following is not true about cyclic electron flow?

Accepted Answer

A) Cyclic electron flow produces more NADPH per photon than noncyclic electron flow. 
B) Cyclic electron flow involves only PSI. 
C) Plastocyanin is required for cyclic electron flow. 
D) Cyclic electron flow leads to the build-up of a proton gradient. 
E) Cyclic electron flow does not produce O2. 
A) Cyclic electron flow produces more NADPH per photon than noncyclic electron flow. 
B) Cyclic electron flow involves only PSI. 
C) Plastocyanin is required for cyclic electron flow. 
D) Cyclic electron flow leads to the build-up of a proton gradient. 
E) Cyclic electron flow does not produce O2. A

Question 2

Consider a liver cell carrying out the oxidation of glucose under aerobic conditions.Suppose that we added a very potent and specific inhibitor of the mitochondrial ATP synthase,completely inhibiting this enzyme.Indicate whether each of the following statements about the effect of this inhibitor is true or false;if false,explain in a sentence or two why it is false.
____ (a)ATP production in the cell will quickly drop to zero.
____ (b)The rate of glucose consumption by this cell will decrease sharply.
____ (c)The rate of oxygen consumption will increase.
____ (d)The citric acid cycle will speed up to compensate.
____ (e)The cell will switch to fatty acid oxidation as an alternative to glucose oxidation,and the inhibitor will therefore have no effect on ATP production.

Accepted Answer

A) True 
 B)False  False

Question 3

In the photolytic cleavage of water by the oxygen-evolving complex [2H2O $\rightarrow$ 4 H+ + 4e- + O2],how many photons of light at a wavelength of 680 nm are required?

Accepted Answer

A) 1 
B) 2 
C) 4 
D) 6 
E) 8 
A) 1 
B) 2 
C) 4 
D) 6 
E) 8 C

Question 4

Plants carrying out photosynthesis produce O2.Describe the source of this O2,and explain,with chemical equations or schematic diagrams,why O2 production occurs only during daylight hours.

Accepted Answer

O₂ is generated by the splittin

Question 5

Show the path of electrons from photosystem II to NADPH in the chloroplast.What is the source of the energy that moves electrons through this path? Show where oxygen is involved in this pathway.

Accepted Answer

H₂O @#LAT-DLM& P680 @#LAT-DLM& Pheophytin @#LAT-DLM& PQA@#LAT-DLM&PQB

Question 6

Given that ~8 photons are required to produce one molecule of O2,roughly how many photons are required to produce one molecule of glucose.

Accepted Answer

Since the overall reaction of photosynth

Question 7

The experimental determination of the effectiveness of light of different colors in promoting photosynthesis is called the:

Accepted Answer

A) absorption spectrum. 
B) action spectrum. 
C) difference spectrum. 
D) reflectance spectrum. 
E) refraction spectrum. 
A) absorption spectrum. 
B) action spectrum. 
C) difference spectrum. 
D) reflectance spectrum. 
E) refraction spectrum.

Question 8

Which of the following is not true of the proton motive force (pmf)?

Accepted Answer

A) One component of the pmf is the chemical gradient of protons. 
B) One component of the pmf is the charge gradient of protons. 
C) Generation of the pmf in mitochondria requires succinate. 
D) The pmf is generated by the electron transport chain in mitochondria. 
E) The pmf drives ATP synthesis in mitochondria. 
A) One component of the pmf is the chemical gradient of protons. 
B) One component of the pmf is the charge gradient of protons. 
C) Generation of the pmf in mitochondria requires succinate. 
D) The pmf is generated by the electron transport chain in mitochondria. 
E) The pmf drives ATP synthesis in mitochondria.

Question 9

Cyclic electron flow in chloroplasts produces:

Accepted Answer

A) ATP and O2,but not NADPH. 
B) ATP,but not NADPH or O2. 
C) NADPH and ATP,but not O2. 
D) NADPH,but not ATP or O2. 
E) O2,but not ATP or NADPH. 
A) ATP and O2,but not NADPH. 
B) ATP,but not NADPH or O2. 
C) NADPH and ATP,but not O2. 
D) NADPH,but not ATP or O2. 
E) O2,but not ATP or NADPH.

Question 10

Which of the following statements about the chemiosmotic theory is false?

Accepted Answer

A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane. 
B) Energy is conserved as a transmembrane pH gradient. 
C) Oxidative phosphorylation cannot occur in membrane-free preparations. 
D) The effect of uncoupling reagents is a consequence of their ability to carry protons through membranes. 
E) The membrane ATPase,which plays an important role in other hypotheses for energy coupling,has no significant role in the chemiosmotic theory. 
A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane. 
B) Energy is conserved as a transmembrane pH gradient. 
C) Oxidative phosphorylation cannot occur in membrane-free preparations. 
D) The effect of uncoupling reagents is a consequence of their ability to carry protons through membranes. 
E) The membrane ATPase,which plays an important role in other hypotheses for energy coupling,has no significant role in the chemiosmotic theory.

Question 11

In his studies of alcoholic fermentation by yeast,Louis Pasteur noted that the sudden addition of oxygen (O2)to a previously anaerobic culture of fermenting grape juice resulted in a dramatic decrease in the rate of glucose consumption.This "Pasteur effect" can be counteracted by the addition of 2,4-dinitrophenol (DNP),an uncoupler of oxidative phosphorylation.
(a)Why would the yeast cells consume less glucose in the presence of oxygen? Can you estimate how much less glucose they would use? 
(b)Why would DNP counteract or prevent the Pasteur effect?

Accepted Answer

(a)During aerobic oxidation of glucose,t

Question 12

Photophosphorylation differs from oxidative phosphorylation in that the former requires the input of energy in the form of ___________ to create a good electron donor.In photophosphorylation,electrons flow through a series of membrane-bound carriers including ___________ ,___________ ,and ___________ proteins,whereas ___________ are pumped across a membrane to create an ___________ potential.

Accepted Answer

Light;cytochromes;qu

Question 13

The oxidation of a particular hydroxy substrate to a keto product by mitochondria has a P/O ratio of less than 2.The initial oxidation step is very likely directly coupled to the:

Accepted Answer

A) oxidation of a flavoprotein. 
B) oxidation of a pyridine nucleotide. 
C) reduction of a flavoprotein. 
D) reduction of a pyridine nucleotide. 
E) reduction of cytochrome a3. 
A) oxidation of a flavoprotein. 
B) oxidation of a pyridine nucleotide. 
C) reduction of a flavoprotein. 
D) reduction of a pyridine nucleotide. 
E) reduction of cytochrome a3.

Question 14

Which of the following statements about energy conservation in the mitochondrion is false?

Accepted Answer

A) Drugs that inhibits the ATP synthase will also inhibit the flow of electrons down the chain of carriers. 
B) For oxidative phosphorylation to occur,it is essential to have a closed membranous structure with an inside and an outside. 
C) The yield of ATP per mole of oxidizable substrate depends on the substrate. 
D) Uncouplers (such as dinitrophenol)have exactly the same effect on electron transfer as inhibitors such as cyanide;both block further electron transfer to oxygen. 
E) Uncouplers "short circuit" the proton gradient,thereby dissipating the proton motive force as heat. 
A) Drugs that inhibits the ATP synthase will also inhibit the flow of electrons down the chain of carriers. 
B) For oxidative phosphorylation to occur,it is essential to have a closed membranous structure with an inside and an outside. 
C) The yield of ATP per mole of oxidizable substrate depends on the substrate. 
D) Uncouplers (such as dinitrophenol)have exactly the same effect on electron transfer as inhibitors such as cyanide;both block further electron transfer to oxygen. 
E) Uncouplers "short circuit" the proton gradient,thereby dissipating the proton motive force as heat.

Question 15

The compound 2,4-dinitrophenol (DNP),an uncoupler,was briefly used as a weight-loss drug.Some of its effects in people who took the drug included weight loss and higher than normal body temperature.Some people even died.Explain the first two effects of the compound in biochemical terms.

Accepted Answer

The uncoupler allows continuous oxidatio

Question 16

When the F1 portion of the ATP synthetase complex is removed from the mitochondrial membrane and studied in solution,it functions as an ATPase.Why does it not function as an ATP synthetase?

Accepted Answer

Like all enzymes,the F₁ subun

Question 17

Describe,in simple diagrams and a few words,the chemiosmotic theory for coupling oxidation to phosphorylation in mitochondria.

Accepted Answer

There are two central elements in the ch

Question 18

In what order do the following five steps occur in the photochemical reaction centers? 
1)Excitation of the chlorophyll a molecule at the reaction center
2)Replacement of the electron in the reaction center chlorophyll
3)Light excitation of antenna chlorophyll molecule
4)Passage of excited electron to electron-transfer chain
5)Exiton transfer to neighboring chlorophyll

Accepted Answer

A) 1-2-3-4-5 
B) 3-2-5-4-1 
C) 3-5-1-4-2 
D) 4-2-3-5-1 
E) 5-4-3-2-1 
A) 1-2-3-4-5 
B) 3-2-5-4-1 
C) 3-5-1-4-2 
D) 4-2-3-5-1 
E) 5-4-3-2-1

Question 19

Which one of the following statements about photophosphorylation is false?

Accepted Answer

A) It can be uncoupled from electron flow by agents that dissipate the proton gradient. 
B) The difference in pH between the luminal and stromal side of the thylakoid membrane is 3 pH units. 
C) The luminal side of the thylakoid membrane has a higher pH than the stromal side. 
D) The number of ATPs formed per oxygen molecule is about three. 
E) The reaction centers,electron carriers,and ATP-forming enzymes are located in the thylakoid membrane. 
A) It can be uncoupled from electron flow by agents that dissipate the proton gradient. 
B) The difference in pH between the luminal and stromal side of the thylakoid membrane is 3 pH units. 
C) The luminal side of the thylakoid membrane has a higher pH than the stromal side. 
D) The number of ATPs formed per oxygen molecule is about three. 
E) The reaction centers,electron carriers,and ATP-forming enzymes are located in the thylakoid membrane.

Question 20

Show the path of electrons from ubiquinone (Q or coenzyme Q)to oxygen in the mitochondrial respiratory chain.One of the two compounds (Q and O2)has a standard reduction potential (E'°)of 0.82 V,and the other,0.045 V.Which value belongs to each compound? How did you deduce this?

Accepted Answer

QH₂ @#LAT-DLM& cyt b @#LAT-DLM&cyt c₁

Exam 19: Oxidative Phosphorylation and Photophosphorylation

Which of the following is not true about cyclic electron flow?

In the photolytic cleavage of water by the oxygen-evolving complex [2H2O →\rightarrow→ 4 H+ + 4e- + O2],how many photons of light at a wavelength of 680 nm are required?

Plants carrying out photosynthesis produce O2.Describe the source of this O2,and explain,with chemical equations or schematic diagrams,why O2 production occurs only during daylight hours.

Show the path of electrons from photosystem II to NADPH in the chloroplast.What is the source of the energy that moves electrons through this path? Show where oxygen is involved in this pathway.

Given that ~8 photons are required to produce one molecule of O2,roughly how many photons are required to produce one molecule of glucose.

The experimental determination of the effectiveness of light of different colors in promoting photosynthesis is called the:

Which of the following is not true of the proton motive force (pmf)?

Cyclic electron flow in chloroplasts produces:

Which of the following statements about the chemiosmotic theory is false?

The oxidation of a particular hydroxy substrate to a keto product by mitochondria has a P/O ratio of less than 2.The initial oxidation step is very likely directly coupled to the:

Which of the following statements about energy conservation in the mitochondrion is false?

The compound 2,4-dinitrophenol (DNP),an uncoupler,was briefly used as a weight-loss drug.Some of its effects in people who took the drug included weight loss and higher than normal body temperature.Some people even died.Explain the first two effects of the compound in biochemical terms.

When the F1 portion of the ATP synthetase complex is removed from the mitochondrial membrane and studied in solution,it functions as an ATPase.Why does it not function as an ATP synthetase?

Describe,in simple diagrams and a few words,the chemiosmotic theory for coupling oxidation to phosphorylation in mitochondria.

Which one of the following statements about photophosphorylation is false?

Show the path of electrons from ubiquinone (Q or coenzyme Q)to oxygen in the mitochondrial respiratory chain.One of the two compounds (Q and O2)has a standard reduction potential (E'°)of 0.82 V,and the other,0.045 V.Which value belongs to each compound? How did you deduce this?

The Foundations of Biochemistry

Water

Amino Acids, peptides, and Proteins

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

Recombinant Dna Technology

Lipids

Biological Membranes and Transport

Biosignaling

Principles of Bioenergetics

Glycolysis, gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Carbohydrate Biosynthesis in Plants and Bacteria

Lipid Biosynthesis

Biosynthesis of Amino Acids, nucleotides, and Related Molecules

Integration and Hormonal Regulation of Mammalian Metabolism

Genes and Chromosomes

Dna Metabolism

Rna Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

In the photolytic cleavage of water by the oxygen-evolving complex [2H₂O $\rightarrow$ 4 H⁺ + 4e^- + O₂],how many photons of light at a wavelength of 680 nm are required?

Plants carrying out photosynthesis produce O₂.Describe the source of this O₂,and explain,with chemical equations or schematic diagrams,why O₂ production occurs only during daylight hours.

Given that ~8 photons are required to produce one molecule of O₂,roughly how many photons are required to produce one molecule of glucose.

When the F₁ portion of the ATP synthetase complex is removed from the mitochondrial membrane and studied in solution,it functions as an ATPase.Why does it not function as an ATP synthetase?

Show the path of electrons from ubiquinone (Q or coenzyme Q)to oxygen in the mitochondrial respiratory chain.One of the two compounds (Q and O₂)has a standard reduction potential (E'°)of 0.82 V,and the other,0.045 V.Which value belongs to each compound? How did you deduce this?