GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Other Metabolic Processes

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

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Example Questions

Example Question #1 : Other Metabolic Processes

Which of the following mnemonics is helpful in remembering the relationship between anabolism and catabolism?

Possible Answers:

ABCD

PAD

AWSOME

RICE

STEVE

Correct answer:

ABCD

Explanation:

ABCD correlates to anabolism=build catabolism=destroy. Anabolism is the constructive phase of metabolism during which tissues are built. Catabolism is the opposite of anabolism, representing the destructive phase of metabolism. Metabolism is the total of all the chemical changes that take place in the body.

STEVE is the pathway of sperm through the male reproductive system: Seminiferous Tubules, Epididymis, Vas Deferens, Ejaculatory duct. PAD is the layers of the meninges: Piamater, Arachnoid mater, Dura mater. RICE refers to the treatment for an injury to a joint: Rest, Ice, Compression, Elevation. AWSOME is the signs and symptoms of depression: Affect flat, Weight change, Energy loss, Sad feelings, Others (guilt, loss of pleasure, hopelessness), Memory loss, Emotional blunting. 

Example Question #192 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

__________ is an enzyme used to help break down glycogen. The end product is __________.

Possible Answers:

Glycogen phosphatase . . . glucose-1-phosphate

Glycogen phosphatase . . . glucose-6-phosphate

Glycogen phosphorylase . . . glucose-6-phosphate

Glycogen phosphorylase . . . glucose-1-phosphate

Correct answer:

Glycogen phosphorylase . . . glucose-1-phosphate

Explanation:

Phosphorylases are enzymes that attach phosphate groups to acceptors by breaking a chemical bond. Phosphatases are enzymes that remove phosphate groups.

Glycogen catabolism occurs by activation of glycogen phosphorylase, which then catalyzes the reaction of glycogen into glucose-1-phosphate (and a glycogen chain that is one glucose shorter).

Example Question #193 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

__________ helps transfer fatty acids into the mitochondrial matrix.

Possible Answers:

Carnitine

Fatty acid transferase

Acyl-CoA

Biotin

Correct answer:

Carnitine

Explanation:

Carnitine is ultimately responsible for helping fatty acids enter into the mitochondrial matrix. Acyl-CoA is actually the activated fatty acid that is being transferred. Carnitine reacts with acyl-CoA, and the newly formed acyl carnitine is moved into the mitochondrial matrix by a translocase.

Biotin is a vitamin that has many functions, including aiding in fatty acid synthesis. There is no protein that is actually called fatty acid transferase.

Example Question #2 : Help With Catabolism

Which of the following statements about catabolic pathways are not true?

Possible Answers:

Lipids are broken down into glycerol and fatty acids

Macromolecules are only involved in catabolic pathways

Polysaccharides are hydrolyzed to glucose, which can then pass through glycolysis and the citric acid cycle

Proteins are hydrolyzed into their amino acids, which feed into glycolysis or the citric acid cycle

Polysaccharides eventually release energy in the form of NADH and ATP

Correct answer:

Macromolecules are only involved in catabolic pathways

Explanation:

Macromolecules, such as peptides, polysaccharides, lipids, and proteins can be broken down to provide energy as well as operate in reverse through anabolic pathways. Anabolic and catabolic processes can occur simultaneously. All of the other answers are true. 

Example Question #3 : Help With Catabolism

Which of the following cellular processes is defined as a catabolic reaction?

Possible Answers:

Protein synthesis

Gluconeogenesis

Gylcolysis

Glycogenesis

Correct answer:

Gylcolysis

Explanation:

A catabolic reaction is defined as a reaction in which a large molecule is broken down into smaller subunits. Of the following options, all listed are anabolic except for glycolysis. Glycolysis is the process of converting a glucose molecule into 2 pyruvate molecules, which classifies it as catabolic in nature.

Example Question #1 : Other Metabolic Processes

Which of the following choices is a likely response to low blood glucose levels?

I. Phosphorylation of glycogen phosphorylase

II. Phosphorylation of glycogen synthase

III. Enhanced production of insulin

Possible Answers:

I and II

I and III

II and III

I only

Correct answer:

I and II

Explanation:

When blood glucose levels are low, the obvious bodily response is to create more free glucose. Glycogen phosphorylase is an enzyme that is responsible for freeing glucose monomers from glycogen (thus creating more free glucose and raising the blood glucose concentration). Phosphorylation of glycogen phosphorylase activates the enzyme to create more free glucose. Thus, statement I should appear in our answer.

Glycogen synthase is an enzyme that does just the opposite; it traps free-floating glucose monomers by adding them to glycogen chains. Phosphorylation of glycogen synthase inhibits the enzyme's function to create more free glucose. Thus, statement II should also appear in our answer.

Increasing the production of insulin would lower blood glucose levels even further (glucagon, another hormone, would help raise them). Thus, statement III should not appear in our answer.

The final answer is statements I and II.

Example Question #195 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

Antidiuretic hormone (ADH) is produced in the pituitary gland and then secreted into the blood stream. What is the function of ADH? 

Possible Answers:

Secreted ADH decreases the reabsorbtion of sodium and chloride in the ascending loop of Henle by binding and inhibiting the ATP-dependent sodium/chloride pumps

Secreted ADH stimulates the reabsorption of glucose by increasing the number of glucose-2 transporters in the nephron proximal tubule

Secreted ADH stimulates the pancreas to secrete more insulin by binding specific receptors in pancreatic capillaries

Secreted ADH decreases the amount of water reabsorbed in the nephron by stimulating the ATP-dependent closure of aquaporins in the collecting duct

Secreted ADH increases the amount of water reabsorbed from the nephron into the bloodstream by increasing the number of aquaporins in the collecting duct 

Correct answer:

Secreted ADH increases the amount of water reabsorbed from the nephron into the bloodstream by increasing the number of aquaporins in the collecting duct 

Explanation:

Antidiuretic hormone (ADH) binds the ADH receptors in the basolateral membrane of the collecting duct, which, through an ATP-dependent signaling cascade, synthesizes and relocates aquaporin-2 to the apical membrane of the collecting duct epithelial cells. The increase of aquaporin-2 at this membrane location facilitates increased water reabsorbtion into the bloodstream. 

Example Question #2 : Help With Metabolic Regulation And Hormones

Which of the following cellular processes is NOT stimulated by insulin? 

Possible Answers:

Glycogenesis

Cholesterol synthesis

Glycolysis

Lipolysis

Correct answer:

Lipolysis

Explanation:

Insulin is a hormone that can often be associated with post-meal metabolism. The body has just eaten a meal, and is sequestering all of the nutrients and vitamins in the food. As a result, insulin is often associated with anabolic processes: glycogenesis, cholesterol and protein synthesis, and lipogenesis. Lipolysis, or the breaking down of fatty acids, is observed in periods of starvation, and therefore would not be stimulated by insulin.

Example Question #1 : Help With Metabolic Regulation And Hormones

Which enzyme would be inhibited in the body following a carbohydrate-heavy meal?

Possible Answers:

Fructose-1,6-bisphosphatase

Glucokinase

PFK-1

Glycogen synthase

Correct answer:

Fructose-1,6-bisphosphatase

Explanation:

After eating a carbohydrate-heavy meal, the body is not going to have any problem getting access to glucose. As a result, the body is going to activate enzymes needed for bringing glucose into cells and storing/using it. This includes glucokinase, PFK-1, and glycogen synthase. Fructose-1,6-bisphosphatase is an enzyme used in gluconeogenesis. Since the body does not need to create glucose following the meal, this enzyme is inhibited.

Example Question #1 : Help With Other Metabolic Processes

What is the primary purpose of fermentation?

Possible Answers:

Generate ethanol

Regenerate NAD+

Generate oxygen

Generate ATP

Correct answer:

Regenerate NAD+

Explanation:

The primary purpose of fermentation is to regenerate the NAD+ that was reduced to NADH during glycolysis. This is essential because the cell will need that NAD+ to be able to go through glycolysis. In anaerobic environments, the Krebs cycle and electron transport chain cease to function, leaving glycolysis as the primary metabolic process for the cell to generate ATP. NAD+ is an essential reactant for glycolysis, but is rapidly consumed when the electron transport chain is not running. Fermentation takes place in order to replenish this reactant and allow glycolysis to continue.

Ethanol and lactic acid can be products of fermentation, but are not the primary purpose for fermentation. No oxygen or ATP is generated during this process.

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