GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Biochemistry

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

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Example Questions

Example Question #1 : Help With Glycolysis

In what cellular compartment does the process of glycolysis occur?

Possible Answers:

Cytosol

Nucleus

Endoplasmic reticulum

Mitochondrial inner membrane

Mitochondrial outer membrane

Correct answer:

Cytosol

Explanation:

Both phases of glycolysis occur in the cytosol of the cell. The products of glycolysis are moved for further processing into the mitochondria, but the conversion of glucose to pyruvate is a cytosolic reaction. 

Example Question #1 : Cellular Respiration And Photosynthesis

Glycolysis converts molecules of glucose into pyruvate. Glycolysis consists of two phases: the preparatory phase (which consumes ATP) and the pay-off phase (which produces ATP). Which of these correctly indicates the number of ATPs consumed in the preparatory phase, and the number of ATPs generated in the pay-off phase of anaerobic glycolysis. 

Possible Answers:

2 ATP consumed, 4 ATP produced

2 ATP consumed, 2 ATP produced

4 ATP consumed, 2 ATP produced

6 ATP consumed, 2 ATP produced

3 ATP consumed, 3 ATP produced

Correct answer:

2 ATP consumed, 4 ATP produced

Explanation:

The initial energy investment required for conversion of one glucose to pyruvate is 2 ATP in the preparatory phase. In the pay-off phase, substrate level phosphorylation produces a total of 4 ATP per initial glucose. 

Example Question #1 : Cellular Respiration And Photosynthesis

Pyruvate must be oxidized into acetyl-CoA in order to enter the citric acid cycle. Which of the following answers contains the inputs required for this process per one molecule of pyruvate? 

Possible Answers:

, coenzyme A

Correct answer:

, coenzyme A

Explanation:

 and  are the resultant molecules from this conversion, not the inputs.  and  are important molecules in the citric acid cycle, but are not required for this particular oxidation step.  must be reduced to , and coenzyme A is a crucial modulator of these reactions. Thus,  and coenzyme A are the required inputs for the oxidation of pyruvate to acetyl CoA. 

Example Question #1 : Help With Glycolysis

A student isolates starch and provides it as nutrients to a cell culture in anaerobic conditions. What additional steps, if any, does the student have to take to facilitate energy production in the cells?

Possible Answers:

The student has to provide aerobic conditions instead

The student has to add glucosidases

The student has to add glycogen instead of starch

The student has to do nothing; the cells will utilize starch and produce energy

Correct answer:

The student has to add glucosidases

Explanation:

Starch is a complex carbohydrate that is digested by enzymes in the small intestine. These digestive enzymes, called glucosidases, are released by exocrine glands in humans and are involved in breakdown of complex carbohydrates to their individual monomers (glucose). Recall that energy production in cell begins with glycolysis, where a molecule of glucose is metabolized to produce intermediates for subsequent metabolic steps. Cells can’t use starch or glycogen during glycolysis; therefore, the student must add glucosidase to break down starch into individual glucose molecules.

Energy can be produced in anaerobic conditions (like in glycolysis). It might not have a high yield of energy such as aerobic respiration, but the cells can still produce energy when they are oxygen deficient. As mentioned, glycogen is a complex carbohydrate; therefore, adding it without glucosidase will not help facilitate energy production.

Example Question #1 : Cellular Respiration And Photosynthesis

Anaerobic metabolism occurs in the __________; fermentation occurs in the __________.

Possible Answers:

mitochondria . . . cytoplasm

mitochondria . . . mitochondria

cytoplasm . . . cytoplasm

cytoplasm . . . mitochondria

Correct answer:

cytoplasm . . . cytoplasm

Explanation:

Anaerobic metabolism, such as glycolysis and fermentation, occur in the cellular cytoplasm. The products of glycolysis are transported to the mitochondria where they undergo Krebs cycle (in mitochondrial matrix) and oxidative phosphorylation (on the inner mitochondrial membrane). Both Krebs cycle and oxidative phosphorylation require oxygen and are, therefore, called aerobic metabolism.

Example Question #9 : Help With Glycolysis

Which of the following is true regarding glycolysis?

Possible Answers:

All of the carbons from the glycolysis input are transferred to pyruvate 

FAD is reduced during glycolysis

ATP is produced but not utilized during glycolysis

More than one of these are true

Correct answer:

All of the carbons from the glycolysis input are transferred to pyruvate 

Explanation:

Glycolysis is an anaerobic process that produces 2 net ATP, 2 pyruvate molecules, and 2 NADH. Pyruvate is a three-carbon molecule. Recall that glucose is a six-carbon molecule; therefore, the six-carbon glucose is broken down to two three-carbon pyruvate molecules. This means that all the carbons in glucose are transferred to the pyruvate molecules. ATP is produced and consumed in glycolysis. There is a total of four ATP molecules synthesized in the glycolysis; however, glycolysis consume two ATP molecules so you get a net of 2 ATP molecules. Finally, glycolysis involves the reduction two  molecules to yield two NADH molecules (not FAD).

Example Question #11 : Cellular Respiration And Photosynthesis

How many molecules of pyruvate are produced from one molecule of glucose during glycolysis?

Possible Answers:

Correct answer:

Explanation:

The starting molecule in glycolysis is glucose, a six-carbon molecule while the ending molecule in glycolysis is pyruvate, a three-carbon molecule. During glycolysis glucose is split and its six carbons are used to make 2 molecules of three-carbon pyruvate because. Note that no carbon dioxide is released during glycolysis, but since aerobic metabolism (starting with the Krebs cycle) uses acetyl-CoA as a substrate, which is two carbons long, one molecule of carbon dioxide is released for each molecule of pyruvate produced during glycolysis.

Example Question #12 : Cellular Respiration And Photosynthesis

Which of the following is true regarding glycolysis?

Possible Answers:

Glycolysis occurs in every cell

Glycolysis produces 4 net ATP

The inputs for glycolysis include glycogen and glucose

More than one of these are correct

Correct answer:

Glycolysis occurs in every cell

Explanation:

Glycolysis is the first step in producing ATP. Glycolysis is an anaerobic process that occurs in every cell. Certain cells, such as red blood cells, only rely on glycolysis for energy. In most of the other cells, glycolysis produces ATP and few intermediates that will be used in subsequent steps to generate more ATP; therefore, glycolysis occurs in every cell.

The major input for glycolysis is glucose. Glycogen, a storage form of glucose, needs to be broken down into individual glucose units before undergoing glycolysis. The net products of glycolysis are 2 NADH, 2 pyruvate molecules, and 2 ATP. There is a total of 4 ATP produced in glycolysis; however, two of the ATP molecules are consumed, leaving behind only 2 net ATP.

Example Question #12 : Cellular Respiration And Photosynthesis

The first step of glycolysis hydrolyzes ATP to ADP and inorganic phosphate. What happens to the glucose molecule during this step?

Possible Answers:

The glucose is converted to fructose

The glucose is phosphorylated

Glucose is cleaved into two molecules of pyruvate

The glucose is dephosphorylated

The glucose is cleaved into two molecules of glyceraldehyde-3-phosphate

Correct answer:

The glucose is phosphorylated

Explanation:

The first step of glycolysis consumes a molecule of ATP, removing one of the phosphate groups to make ADP. This phosphate group is added to glucose to make Glucose-6-phosphate, therefore glucose is phosphorylated.

Example Question #13 : Cellular Respiration And Photosynthesis

What enzyme converts glyceraldehyde-3-phosphate to 1, 3-bisphosphoglyceric acid during glycolysis? 

Possible Answers:

Pyruvate kinase 

Fructose-bisphosphate aldolase 

Enolase 

Glyceraldehyde-3-phosphate dehydrogenase

Phosphoglycerate kinase 

Correct answer:

Glyceraldehyde-3-phosphate dehydrogenase

Explanation:

The correct answer is glyceraldehyde-3-phosphate dehydrogenase. This enzyme sequesters a hydrogen from carbon 4 on glyceraldehyde 3-phosphate to reduce  to , and in its place, an inorganic phosphate molecule is transferred to this position. Fructose-bisphosphate aldolase converts Fructose-1, 6-bisphosphate to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. Pyruvate kinase converts phosphoenolpyruvate to pyruvate whereas enolase converts 2-phosphoglycerate to phosphoenolpyruvate. Phosphoglycerate kinase converts 1, 3-bisphosphoglycerate to 3-phosphoglycerate. 

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

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