biochem - LA8

Which of the following situations or phrases most accurately describes the citric acid cycle?

"All roads lead to Rome."

cytochrome c evolved at least _____ years ago.

1.5 billion

Out of 100,000 people, how many would be expected to have a mitochondrial disease?

10

Which of the following best describes the net organic products formed during the oxidation of one molecule of glucose to two molecules of pyruvate via glycolysis

2ATP+2NADH

If glucose is labeled with 14C at the C1 position only, which of the following would occur if the glucose underwent glycolysis?

50% of the pyruvate would contain 14C.

ATP synthase catalyzes the synthesis of ATP from:

ADP and Pi.

What is substrate level phosphorylation?

ATP synthesis when the phosphate donor is a substrate with high phosphoryl transfer potential

What is a common mechanistic feature of kinases?

Binding of substrate causes a large conformation change that results in cleft closing.

Well into exercise, the ratio of ATP/AMP in muscle cells decreases. What effect does this ratio reduction have on the activity of phosphofructokinase and pyruvate kinase?

Both enzymes are increased in activity due to lack of allosteric binding of ATP.

Which part of oxidative phosphorylation is inhibited by cyanide?

Complex IV

Which of the following describes the direction of proton movement relative to electron transfer and phosphorylation?

Electron transfer pumps protons out of the matrix. As the protons reenter through the ATP synthase, ATP is produced in the matrix.

In cells, NADH serves as a carrier of which of the following:

Electrons

The path taken by electrons to water from NADH generated during the citric acid cycle will NOT pass though

FAD

What is the source of electrons at complex II (succinate-Q-reductase)?

FADH2 from the citric acid cycle

Electrons from _____ enter the respiratory chain at _____, otherwise known as _____.

FADH2; succinate-Q reductase complex; Complex II

Which of the following is not an intermediate in the glycolytic pathway by which glucose is oxidized to pyruvate

Glucose 1-phosphate

Cancer cells utilizing aerobic glycolysis use what amino acid to replenish citric acid cycle components in the mitochondria?

Glutamine

Which of the following is NOT a part of the Mitchell chemiosmotic hypothesis?

High-energy phosphorylated intermediates that serve as phosphate donors to ADP are generated as a result of electron-transfer reactions.

As electrons flow through complexes _____, protons are transported across the _____ mitochondrial membrane.

I, III, and IV; inner

Which of the following is true of coenzyme Q (ubiquinone) but not cytochrome c?

It can carry two e—.

Succinyl CoA synthetase catalyzes a double-displacement reaction. Which one of the following best describes the covalently modified enzyme?

It contains a phosphorylated histidine.

Which of the following must be regenerated for glycolysis to proceed?

NAD+

Which of the following best characterizes NADH and NADPH:

NADH is primarily used for ATP generation, whereas NADPH is primarily used for biosynthesis

Which of the following glycolytic reactions constitutes a major thermodynamic driving force for glycolysis in vivo

Phosphoenolpyruvate + ADP to pyruvate + ATP

In order for an electron transfer reaction to be energetically spontaneous, which of the following must be TRUE?

The change in reduction potential, ΔEo, must be positive.

In going from acetyl-CoA to succinate, two carbons have entered the cycle and two have been released as CO2. Why is the cycle not considered as complete at this point?

The oxaloacetate used to initiate the cycle must be regenerated.

HIF-1 is activated by which of the following?

Tumor growth, exercise

In the reaction catalyzed by succinyl-CoA synthetase

a succinylphosphate transfers its phosphate to a histidyl residue.

Movement within the F1 subunit of ATP synthase begins when a proton moves through half of the _____ subunit, then transfer to the _____ subunit by interaction with a _____ residue.

a; c; Glu

In the first step of the citric acid cycle, it is important that side reactions such as undesired hydrolysis to release _____ be minimized.

acetate

Which of the following enzymes has a unique four irons complexed with 4 inorganic sulfides and and 3 cysteine sulfur atoms and that is involved in the net synthesis of oxaloacetate from acetyl CoA?

aconitase

ATP synthase can bind ATP in which subunit(s)?

alpha and beta

Which one of the following best describes the order of events in the citrate synthase mechanism? Oxaloacetate binds _____ acetyl CoA; citrate leaves _____ CoA.

before; after

Which subunit of ATP synthase consists of transmembrane helices that contain a Glu or Asp residue in the center?

c

Complex I is the entry point of NADH from:

citric acid cycle, glycolysis

Which of the following describes the reaction catalyzed by aconitase in the conversion of citrate to isocitrate?

conversion of a tertiary alcohol to a secondary alcohol

The glycerol 3-phosphate shuttle is used to bring in electrons arising from:

cytoplasmic NADH.

What are the primary metabolic fates of pyruvate?

ethanol, acetyl CoA, lactate

ATP is a substrate for citrate synthase.

false

Which of the following stimulates phosphofructokinase in the liver?

fructose 2,6-bisphosphate

What two 3-carbon molecules are generated by the cleavage of fructose-1,6-bisphosphate?

glyceraldehyde-3-phosphate and dihydroxyacetone phosphate

Which of the following reduced substances came from a reaction with the highest (i.e., positive or least negative) reduction potential?

h2o

The three major regulatory enzymes in the glycolytic pathway are

hexokinase, phosphofructokinase, and pyruvate kinase.

Glucose 6-phosphate inhibits the dominant form of hexokinase in which tissues?

liver, muscle

Which of the following citric acid cycle intermediates would become depleted if malonate, a competitive inhibitor of succinate dehydrogenase, were present?

malate

Which of the following enzymes is correctly paired with its product if the citric acid cycle is operating to oxidize acetyl CoA?

malate dehydrogenase: oxaloacetate

The process of glycolysis occurs in the cytoplasm. The electrons from the NADH generated during glycolysis

may enter the electron transport chain either at the level of NADH or FADH2, depending on the shuttle system used to transport them into the mitochondria.

GLUT 4 transporters are found in:

muscle and fat cells.

Which of the following groups is CORRECT? Each group contains an enzyme, and a regulator.

muscle pyruvate kinase; ATP

In oxidative phosphorylation, the _____ of _____ is converted to the _____ of/across _____.

none of the above - electron transfer potential; NADH and FADH2; phosphoryl transfer potential; ATP

What type of organism cannot survive in the presence of oxygen?

obligate anaerobes

What is the function of glyceraldehyde 3-phosphate dehydrogenase?

oxidation of an aldehyde by NAD+ and formation of acyl-phosphate

Oxygen is not used at any point in the citric acid cycle. However, the cycle will not work without oxygen because

oxygen is needed to regenerate electron carriers.

Fermentation does not require _____ to occur, but it does require _____ and _____.

oxygen; organic compounds; oxidation-reduction reactions

Mitochondrial genotype is determined:

primarily from egg DNA.

If pyruvate labeled with 14C at carbon 1 were provided to a cell extract containing the enzymes and cofactors of the glycolytic pathway, the citric acid cycle, and the pyruvate dehydrogenase complex, where would the labeled carbon be lost as CO2?

pyruvate oxidation

What reaction is catalyzed by aldolase?

reversible cleavage of F-1,6-BP to DHAP and GAP

Which one of the following best indicates why citrate needs to be isomerized?

so that it can be oxidatively decarboxylated

Of the enzymes of the citric acid cycle, which is not a freely soluble enzyme?

succinate dehydrogenase

Which of the following is embedded in the inner mitochondrial membrane?

succinate dehydrogenase

Of the electron transfer complexes associated with the inner mitochondrial membrane, which is not involved in generation of a proton gradient?

succinate-Q reductase (complex II)

A person suffering from beriberi (deficiency of vitamin B1) lacks the ability to readily produce

succinyl CoA.

Since citrate synthase exhibits sequential, ordered kinetics:

the order of binding of the substrates matters, and both must bind before the transition state forms.

For the reaction catalyzed by citrate synthase, which of the following is the driving force to make the reaction significantly exergonic?

thioester hydrolysis

What is the purpose of phosphorylating glucose in the cytosol?

to trap glucose in the cell, to destabilize glucose and facilitate the next series of metabolic steps

The conversion of pyruvate to ethanol involves chemical reaction(s) catalyzed by _____ enzyme(s); the conversion of pyruvate to lactate involves chemical reaction(s) catalyzed by _____ enzyme(s).

two; one

Which enzyme of the citric acid cycle most closely resembles the pyruvate dehydrogenase complex in terms of its structure, organization, and the reaction it performs?

α-ketoglutarate dehydrogenase

Which subunit(s) in the F1 component of ATP synthase are part of the moving part (rotor)?

γ and ε