exam 3 practice test 1

How are reactive oxygen species dealt with in the cell? a. Reactive oxygen species are converted to water and oxygen by superoxide dismutase and catalase. b. The radicalized oxygen is exported outside the cell by transporters. c. The cell does not do anything to remove the reactive oxygen species. d. The reactive oxygen species are reduced in the electron transport chain. e. Cytochrome c oxidase accepts the reactive oxygen species and converts the electrons into the proton gradient.

a. Reactive oxygen species are converted to water and oxygen by superoxide dismutase and catalase.

In the Calvin cycle, ______ acts catalytically, similar to oxaloacetate in the ______. a. Ribulose 1,5-bisphosphate; citric acid cycle b. Lactate; Cori cycle c. Malate; malate-aspartate shuttle d. NADH; electron transport chain e. Transketolase; glycolysis pathway

a. Ribulose 1,5-bisphosphate; citric acid cycle

Inhibition of the ATP synthase also leads to an inhibition of the electron transport chain. Why? a. The pumps can no longer pump protons against the increasing proton gradient b. ADP acts as an inhibitor of Complex I c. The ATPase complex functionally localizes near protons pumps to enhance their activity d. The increase in pH in the intermembrane space begins to degrade the inner mitochondrial membrane e. None of the above

a. The pumps can no longer pump protons against the increasing proton gradient

Which of the following statements is TRUE concerning the regulation of the citric acid cycle? a. Acetyl CoA upregulates the conversion of pyruvate to acetyl CoA. b. ADP downregulates the conversion of isocitrate to alpha-ketogluterate. c. NADH upregulates the conversion of citrate to isocitrate d. ADP upregulates the conversion of pyruvate to acetyl CoA. e. ATP upregulates the conversion of succinate to fumarate.

d. ADP upregulates the conversion of pyruvate to acetyl CoA.

In chloroplasts, two photosystems are used to turn light energy into high-energy electrons. The cell balances the output of the two photosystems using a process called: cyclic photophosphorylation. What is the best description of this process? a. Electrons are directly transferred between the two photosystems to keep the number of electrons in each equal. b. Electrons from PSI are transferred from ferredoxin to cytochrome b6f. c. PSII uses plastocyanin instead of water as an electron donor. d. Ferredoxin-NADP+ reductase is activated by plastoquinone from PSII. e. PSII and PSI complexes are separated or fused together to regulate their relative activity.

b. Electrons from PSI are transferred from ferredoxin to cytochrome b6f.

In the electron transport chain ubiquinone (coenzyme Q or Q) is the acceptor of electrons from both NADH and FADH 2. Why then does the cell produce more ATP from the electrons from NADH than it does from electrons coming from FADH2? a. The reduction potential E'o of FADH2 (E'o = -0.22) means it's electrons must first be transferred to NADH (E'o = -0.32). b. FADH2 transfers electrons to complex II, which does not transport protons. c. Nearly half the FADH2 is used as the energy source for substrate level phosphorylation. d. The Qs carrying electrons from NADH are better able to transfer electrons to cytochrome C. e. None of the above

b. FADH2 transfers electrons to complex II, which does not transport protons.

Glycogenin is protein involved in glycogen metabolism. Which of the following statements about Glycogenin is TRUE? a. Glycogenin uses glucose 6-phosphate as a substrate during glycogen synthesis. b. Glycogenin catalyzes the addition of eight molecules of glucose to itself (on an internal tyrosine residue). c. Glycogenin transfers 7 or more glucose residues to form branches in glycogen. d. Glycogenin will add glucose residues to the ends of any glycogen chains with an α 1,4 linkage. e. Glycogenin removes glucose molecules that are linked in an α 1,6 linkage that are closer that 4 residues to another α 1,6 linkage.

b. Glycogenin catalyzes the addition of eight molecules of glucose to itself (on an internal tyrosine residue).

In which subcellular compartment does pyruvate dehydrogenase carry out its catalytic activity in eukaryotes? a. Cytosol b. Mitochondrial matrix c. Intermembrane Space d. Inner mitochondrial membrane e. Outer mitochondrial membrane

b. Mitochondrial matrix

Hers disease is caused by mutations in the liver form of glycogen phosphorylase and often has mild symptoms. In contrast von Gierke disease, which is caused by mutations in glucose 6-phosphatase, has severe symptoms including severe hypoglycemia (low blood sugar). Based on your knowledge of glycogen and glucose metabolism, which is the MOST LIKELY reason that that von Gierke disease has more severe symptoms than Hers disease? a. Glucose 6-phosphatase is the committed step for glycogen degradation so mutations have a bigger effect on the pathway. b. Mutations in glucose 6-phosphatase affect metabolism of the glucose produced by both glycogen degradation and gluconeogenesis. c. Mutations in the liver isoform of glycogen phosphorylase cause the muscle isoform to be expressed in liver. d. Because of reciprocal regulation, mutations in glycogen phosphorylase cause increased glycogen synthesis in liver cells and this causes lower blood sugar levels. e. Mutations in glycogen phosphorylase disrupt normal hormonal regulation of glycogen levels and lead to mild symptoms.

b. Mutations in glucose 6-phosphatase affect metabolism of the glucose produced by both glycogen degradation and gluconeogenesis.

Pyruvate dehydrogenase converts pyruvate to acetyl CoA. This complex enzyme contains both catalytic and stoichiometric coenzymes. Which of the following is a stoichiometric coenzyme? a. Thiamine pyrophosphate b. Lipoic acid c. CoA d. FAD+ e. All the above are stoichiometric coenzymes.

c. CoA

When the light reactions are active, conditions of the stroma change. These changes activate the Calvin cycle. Which of the following statements about the conditions in the stroma is TRUE? a. Concentration of protons increases b. Concentration of magnesium decreases c. Concentration of NADPH increases d. Ferredoxin becomes oxidized e. Cytochrome b6f is released from the membrane into the stroma

c. Concentration of NADPH increases

Which class of enzymes are involved in the production of high-transfer potential electrons in the citric acid cycle? a. Synthase b. Synthetase c. Dehydrogenase d. Kinase e. Isomerase

c. Dehydrogenase

What is the significance of the number of subunits in the c ring found in the F0 portion of the mitochondrial ATP synthase? a. Determines the spin rate of the c ring b. Affects the efficiency of proton loading onto subunit a c. Dictates the number of protons transported to generate one molecule of ATP d. Regulates the number of β subunits in the T conformation e. None of the above

c. Dictates the number of protons transported to generate one molecule of ATP

What effect does uncoupling the electron transport chain have? a. A more extreme proton gradient is formed. b. The mitochondria die from shivering thermogenesis. c. Nonshivering thermogenesis occurs the expense of the proton gradient. d. Increased ADP to ATP conversion by ATP synthase. e. Uncoupling the electron transport chain has no metabolic impact

c. Nonshivering thermogenesis occurs the expense of the proton gradient.

Which of the following statements about hormonal regulation of glycogen breakdown is TRUE? a. Glycogen breakdown is regulated independently from glycolysis and gluconeogenesis. b. Once glycogen phosphorylase is hormonally activated, it remains active until it is turned off by another hormonal signal. c. Glucagon reduces glycogen degradation in muscle cells. d. Epinephrine stimulates glycogen degradation in muscles. e. Insulin regulates glycogen degradation by activating a receptor tyrosine kinase that directly phosphorylates glycogen phosphorylase.

d. Epinephrine stimulates glycogen degradation in muscles.

Which is a TRUE statement about the breakdown of glycogen? a. The longest glucose chain is used first and completely removed before a second chain is targeted. b. Glucose is released by α-1,6-glucosidase (debranching enzyme) as glucose 1phosphate. c. Most α-1,4 linkages are cleaved by down by transferase d. Glycogen phosphorylase releases an activated form of glucose e. Phosphoglucomutase is only involved in glycogen break down in the liver.

d. Glycogen phosphorylase releases an activated form of glucose

In what subcellular location are the majority of the proteins of the electron transport chain located? a. Cytosol b. Mitochondrial matrix c. Intermembrane Space d. Inner mitochondrial membrane e. Outer mitochondrial membrane

d. Inner mitochondrial membrane

Glycogen phosphorylase exists in different forms and conformations under different physiological conditions. In a resting muscle, MOST of the phosphorylase will be in which form? a. Phosphorylase a in the R state b. Phosphorylase a in the T state c. Phosphorylase b in the R state d. Phosphorylase b in the T state e. None of the above

d. Phosphorylase b in the T state

Which of the following describes the organization of the chloroplasts? a. 2 membranes and 3 separate spaces b. 2 membranes and 2 separate spaces c. 4 membranes and 4 separate spaces d. 4 membranes and 3 separate spaces e. 3 membranes and 3 separate spaces

e. 3 membranes and 3 separate spaces

In stage II of the citric acid cycle, succinyl coenzyme A synthetase powers the formation of ATP. Where does the energy for this substrate level phosphorylation come from a. Hydrolysis of GTP b. A proton concentration gradient c. Cleavage of an amide bond d. Hydrolysis of phosphoenolpyruvate e. Cleavage of a thioester bond

e. Cleavage of a thioester bond

Which of the following statements about the regulation of glycogen synthesis is TRUE? a. Glycogen synthase is only regulated by allosteric regulation. b. When glucose levels are low in the blood, protein phosphatase 1 is highly activated. c. Glycogen synthase kinase actually phosphorylates glycogen phosphorylase. d. Eating carbohydrates increases insulin levels in the blood. This down regulates glycogen synthase. e. Protein phosphatase 1 activity up regulates glycogen synthase.

e. Protein phosphatase 1 activity up regulates glycogen synthase.

In chloroplasts, two photosystems are used to turn light energy into high-energy electrons. These electrons are then used for what purpose? a. To generate oxidizing power and an electron gradient b. They transported by high electro-negative carriers to the mitochondria and put through the electron transport chain c. The electrons are used to transport calcium which activates the Calvin cycle d. They are transferred to CO 2 to make it more reactive e. To generate reducing power and a proton gradient

e. To generate reducing power and a proton gradient