biochem questions

Which of the following acts as the substrate to form succinate and ATP

succinyl CoA

which of the following are negative effectors of alpha ketoglutarate

ATP, NADH, Succinyl CoA

There are two important isozymes of acetyl CoA carboxylase enzyme, ACC1 and ACC2. Which of these statements are true?

I. ACC1 catalyzes the synthesis of malonyl CoA while

ACC2 catalyzes carnitine acyltransferase.

II. ACC1 is more active when phosphorylated and ACC2 is more active when dephosphorylated.

III. One of these isoforms exists in the cytosol and the other in the mitochondrial matrix.

III only

Which of the following best describes the effects of glucagon signaling on fatty acid metabolism?

Decrease in fatty acid synthesis and increase in fatty acid breakdown

The enzyme _____ acts as the regulatory step of the pentose phosphate pathway and is primarily controlled by the concentration of _____

glucose 6-phosphate dehydrogenase;
NADP+

The a subunit of ATP synthase

is the entry point for protons from the in-termembrane space

The c-ring of ATP synthase

powers rotation when protons flow through

Glucose-6-phosphate stabilizes the T state of glycogen phosphorylase in muscle cells.

True

The enzyme protein phosphatase 1 (PP1) has the effect of:

I. Removing phosphoryl groups from both phosphorylase kinase and phosphorylase a, inhibiting glycogen degradation.

II. Removing phosphoryl groups from glycogen synthase b, activating glycogen synthesis.

III. Promoting the transfer of fatty acid chains into the mitochondrial matrix.

IV. Promoting the transfer of citrate out of the mitochondrial matrix.

Both I and II

You have a membrane with a membrane potential of 0.11 V, with the inner side of the membrane negatively charged. The pH on the inner side of the membrane is 7.3 and the pH outside the membrane is 6.2. Assume each mole of ATP synthesized takes 50 kJ. How many moles of protons must flow across the membrane to synthesize 5 moles of ATP? R = 8.314 J/mol K; T = 310K; F = 96485 C/mol e-.

15

A marathon runner consumes a large carbohydrate-rich meal the night before a race to "carb load." How does this benefit the runner during the race?

The glycogen built up from carb loading can be broken down into glucose during the race to provide energy to tired muscles.

Given the following reduction data and concentrations, calculate the redox reaction potential for reduction of ubiquinone by succinate. Assume the following concentrations: Q = 6 uM, QH2 = 5 uM,

fumarate = 2 uM, succinate = 4 uM.

Fumarate-² + 2H+ + 2e → E°'= 0.021 succinate-²

Q+ 2H+ + 2é → QH2. E°' = 0.070

• Temperature = 37°C

• R = 8.314 J/mol-K

• F=96,485 C/mol

• pH = 7

0.061

Describe the mechanism for the process of glucose-1-phosphate conversion into UDP glucose

The nucleophilic phosphate attacks the alpha phosphate producing a pyrophosphate

Which of these are true for glycogen degradation?

I. Glycogen phosphorylase can only cleave alpha-1, bonds.

Il. Glycogen phosphorylase is the only enzyme needed

to fully degrade glycogen.

III. Glycogen phosphorylase can cleave alpha-1,4 bonds and alpha-1,6 bonds, but has a higher affinity for the main chain glucose residues.

I only

Which of the following statements is/are true about ketone bodies?

I: They are synthesized in the mitochondria of muscle cells.

Il: Glucagon is a positive hormonal effector for ketone body synthesis.

IlI: Ketone bodies are blood-soluble.

IV: Acetoacetate can be spontaneously decarboxylated to form acetone.

II, III, and IV only

Which of the following enzymes catalyzes the committed step in cholesterol synthesis?

HMG-CoA Reductase

In the muscle, what is the net ATP production when a glycosyl residue is cleaved from glycogen and converted to pyruvate via glycolysis?

3

The outputs of the Pentose Phosphate Pathway vary under different cellular conditions. If a cell is synthesizing a large amount of fatty acids, which of the following will be the major product? Select the best answer.

NADPH

Although fatty acid degradation produces 2 carbon acetyl CoA moieties, the body has mechanisms in place to oxidize odd numbered fatty acid chains. What describes the final steps for this mechanism to bypass this issue?

Propionyl CoA undergoes a carboxylation reaction to add an additional carbon to turn it into succinyl CoA

Which of these fatty acids would yield the least ATP upon complete beta oxidation?

A 12-carbon monounsaturated fatty acid

If the half-reactions below are combined, what is th potential for the spontaneous reaction?

Pyruvate + 2H+ + 2e- → lactate E°’= -0.180

NAD+ + H+ + 2e- → NADH E°’= -0.320

0.140

Which of the following statements is/are true for Complex I of the electron transport chain?

I: It receives electrons from the oxidation of FADH2.

Il: It does not pump H* across the mitochondrial membrane.

III: It receives electrons from the oxidation of NADH.

IV: It ultimately transfers electrons to coenzyme Q fo use in other complexes.

V: It pumps 4 H* across the mitochondrial membrane for each electron carrier that passes its electrons to the complex.

III, IV, and V only

What are the products of the complete oxidation (via the beta oxidation pathway) of a saturated, 16-carbon fatty acid?

8 acetyl-CoA, 7 NADH, 7 FADH2

What conformation does the beta subunit of ATP synthase exist in to trap nucleotides?

Loose

During fatty acid synthesis, intermediates are linked to the ____ group on the acyl carrier protein.

sulfhydryl

What is the cost, in terms of high-energy molecules, of the synthesis of palmitate, a 16-carbon saturated fatty acid? Assume all necessary substrates are already present where synthesis occurs.

7 ATP and 14 NADPH

Which of the following are negative effectors of isocitrate dehydrogenase? Choose the best answer

I: ATP

Il: Succinyl-CoA

III: NADH

IV: Pyruvate

V: Acetyl-COA

I and III only