Exam 2: Clicker Questions

An example of an anabolic pathway is

1. smaller amino acids being linked together to make a protein

2. the tendency to gain or loss weight

3. the burning of fat by exercise

4. a protein being broken down into smaller amino acids

5. none of the above

smaller amino acids being linked together to make a protein

For the reaction shown, what would be the result of this coupling reaction?

1. The overall reaction is spontaneous.

2. The overall reaction is non-spontaneous.

3. The overall free energy is -6 kJ/mol.

4. a and c

5. b and c

a and c

Tauri's disease is a disorder in which phosphofructokinase-1 deficiency occurs. Which of the following would most likely be observed in patients with this disorder?

1. Fructose-6-P levels increase.

2. Fructose-1,6-P levels decrease.

3. ATP levels increase.

4. a and b

5. a andc

a and b

Which of the following is NOT a monosaccharide?

1. Glucose

2. Fructose

3. Galactose

4. Sucrose

Sucrose

Which enzyme catalyzes the rate-limiting step of glycolysis?

1. Hexokinase

2. Phosphofructokinase

3. Pyruvate kinase

4. Enolase

Phosphofructokinase

Under aerobic conditions, what is the primary metabolic fate of pyruvate?

1. Conversion to lactate

2. Conversion to ethanol

3. Conversion to acetyl-CoA for entry into the TCA cycle

4. Conversion to alanine

Conversion to acetyl-CoA for entry into the TCA cycle

Which of the following is a characteristic of anabolic metabolism?

1. Breaking down complex molecules

2. Releasing energy

3. Building up complex molecules

4. Occurring only in the absence of oxygen

Building up complex molecules

Which functional group is responsible for the reducing properties of simple sugars?

1. Hydroxyl group

2. Carbonyl group

3. Carboxyl group

4. Amino group

Carboxyl Group

In glycolysis, glucose is converted to pyruvate. How many carbon atoms does pyruvate contain?

1. 2

2. 3

3. 4

4. 6

3

Which of the following is an allosteric inhibitor of phosphofructokinase in the glycolytic pathway?

1. AMP

2. ATP

3. Fructose-2,6-bisphosphate

4. Citrate

Citrate

Under anaerobic conditions in muscle cells, what is the primary fate of pyruvate?

1. Conversion to acetyl-CoA

2. Conversion to oxaloacetate

3. Conversion to lactate

4. Conversion to ethanol

Conversion to lactate

Where does the citrate cycle occur?

1. cytoplasm

2. mitochondria

3. ribosome

4. endoplasmic reticulum

5. none of the above

Mitochondria

High levels of succinate would result from a deficiency of which enzyme?

1. citrate synthase

2. isocitrate dehydrogenase

3. a-ketoglutarate dehydrogenase

4. succinyl-CoA dehydrogenase

5. succinate dehydrogenase

succinate dehydrogenase

Citric acid is found in high levels in fruit juices. How would drinking several glasses of orange juice affect the citrate cycle?

1. The citrate cycle would not occur, since step 1 produces citrate.

2. Elevated levels of citrate would feed into the cycle to make more ATP equivalents.

3. Step 1 (citrate synthase) would be bypassed.

4. The cycle would go in the reverse manner.

5. b and c

b and c

Why does the citrate cycle produce more energy than glycolysis?

1. It is an aerobic process.

2. It indirectly forms ATP through GTP, NADH, and FADH2.

3. It is a cyclic pathway.

4. a and b

5. b and c

b and c

Low levels of TPP would have what effect?

1. Pyruvate decarboxylase activity would be impaired since TPP is a cofactor.

2. Acetyl CoA levels would be reduced.

3. Pyruvate levels would be increased.

4. all of the above

all of the above

Which electron transport system protein complex is also found in the citrate cycle?

1. complex I

2. complex II

3. complex III

4. complex IV

5. complex V

Complex II

Where is the Q cycle located?

1. complex I

2. complex II

3. complex III

4. complex IV

5. complex V

Complex III

Oligomycin is a complex V inhibitor. If given as an antibiotic, what is the consequence?

1. lowered ATP synthesis

2. reduced NADH oxidation

3. poor cytochrome c reduction

4. increased cytochrome c oxidation

5. increased FAD reduction

lowered ATP synthesis

The malate-aspartate shuttle transfers 2 e- from NADH. Which electron transport system is this linked to?

1. complex I

2. complex II

3. complex III

4. complex IV

5. complex V

complex I

Which process is responsible for the most ATP production?

1. chemiosmotic theory

2. proton-motive force

3. electron-motive force

4. proto-electromotive theory

5. chemi-protomotive force

proton-motive force

Which sequence correctly describes the metabolic fate of glucose carbon under aerobic conditions?

1. Glucose→ Pyruvate → Lactate → Acetyl-CoA → TCA cycle

2. Glucose → Pyruvate → Acetyl-CoA → Citrate → TCA cycle

3. Glucose → Oxaloacetate → Acetyl-CoA → Citrate

4. Glucose → Ethanol → Acetyl-CoA → TCA cycle

Glucose → Pyruvate → Acetyl Co-A → Citrate → TCA cycle

A deficiency of pyruvate dehydrogenase would most directly decrease the production of:

1. Lactate

2. Acetyl-CoA

3. Glucose-6-phosphate

4. Fructose-6-phosphate

Acetyl-CoA

Which pair of enzymes produces NADH during one complete turn of the TCA cycle?

1. Citrate synthase and aconitase

2. Succinate dehydrogenase and fumarase

3. Isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase

4. Succinyl-CoA

Isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase

Phosphofructokinase-1 (PFK-1) is inhibited by citrate. This regulation best illustrates how the TCA cycle can:

1. Stimulate glycolysis when ATP is low

2. Provide feedback inhibition to glycolysis when biosynthetic and energy needs are met

3. Increased pyruvate formation during anaerobic metabolism

4. Directly activate hexokinase

Provide feedback inhibition to glycolysis when biosynthetic and energy needs are met

During aerobic metabolism, pyruvate enters the mitochondrial matrix through the:

1. GLUT2 transporter

2. Monocarboxylate transporter (MCT)

3. Mitochondrial pyruvate carrier (MPC)

4. ATP synthase channel

Mitochondrial pyruvate carrier (MPC)

Which statement best compares ATP production in glycolysis and the TCA cycle?

1. Both pathways generate ATP exclusively through oxidative phosphorylation

2. Glycolysis produces ATP only indirectly through NADH oxidation

3. Glycolysis generates ATP by substrate-level phosphorylation, whereas the TCA cycle directly produces GTP by the substrate-level phosphorylation

4. Neither pathway produces high-energy phosphate compounds directly

Glycolysis generates ATP by substrate-level phosphorylation, whereas the TCA cycle directly produces GTP by the substrate-level phosphorylation

A cell has high levels of ATP, NADH, and acetyl-CoA. According to the lecture slides, which enzyme would most strongly be inhibited?

1. Lactate dehydrogenase

2. Pyruvate dehydrogenase

3. Fumarase

4. Triose phosphate isomerase

Pyruvate dehydrogenase

Which metabolic intermediate serves as the direct link between glycolysis and the TCA cycle?

1. Citrate

2. Oxaloacetate

3. Acetyl-CoA

4. Succinyl-CoA

Acetyl-CoA

Pyruvate carboxylase and pyruvate dehydrogenase utilize the same substrate but generate different products. Which pairing is correct?

1. Pyruvate dehydrogenase → Oxaloacetate; Pyruvate carboxylase → Acetyl-CoA

2. Pyruvate dehydrogenase → Citrate; Pyruvate carboxylase → Malate

3. Pyruvate dehydrogenase → Acetyl-CoA; Pyruvate carboxylase → Oxaloacetate

4. Pyruvate dehydrogenase → Lactate; Pyruvate carboxylase → Citrate

Pyruvate dehydrogenase → Acetyl-CoA; Pyruvate carboxylase → Oxaloacetate

A hepatocyte is exposed to conditions that markedly increase mitochondrial citrate export to the cytosol. Which metabolic consequence would most directly result from this change?

1. Activation of PFK-1 and increased glycolytic flux

2. Inhibition of PFK-1 and decreased glycolytic flux

3. Activation of pyruvate kinase and increased lactate production

4. Increased glucose uptake through GLUT transporters

Inhibition of PFK-1 and decreased glycolytic flux

A mutation abolished the activity of the mitochondrial pyruvate carrier (MPC). Which metabolite would be expected to accumulate in the cytosol despite adequate oxygen availability?

1. Citrate

2. Succinyl-CoA

3. Pyruvate

4. Oxaloacetate

Pyruvate

Which pair of reactions collectively accounts for the complete oxidative decarboxylation of pyruvate carbon before electrons are transferred to the electron transport chain?

1. Pyruvate kinase and citrate synthase

2. Pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase

3. Pyruvate carboxylase and malate dehydrogenase

4. Hexokinase and isocitrate dehydrogenase

Pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase

Which enzyme functions at a critical branch point, determining whether pyruvate enters the TCA cycle for energy production or contributes to replenishing TCA intermediates?

1. Pyruvate kinase

2. Lactate dehydrogenase

3. Pyruvate dehydrogenase

4. Pyruvate carboxylase

Pyruvate carboxylase

During active oxidative metabolism, inhibition of pyruvate dehydrogenase would most directly reduce the activity of which TCA cycle enzyme due to decreased substrate availability?

1. Citrate synthase

2. Aconitase

3. Fumarase

4. Malate dehydrogenase

Citrate synthase