Help with Catabolism

Help Questions

GRE Subject Test: Biochemistry, Cell, and Molecular Biology › Help with Catabolism

Questions 1 - 4
1

__________ helps transfer fatty acids into the mitochondrial matrix.

Carnitine

Acyl-CoA

Fatty acid transferase

Biotin

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.

2

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

Gylcolysis

Glycogenesis

Gluconeogenesis

Protein synthesis

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.

3

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

Macromolecules are only involved in catabolic pathways

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

Lipids are broken down into glycerol and fatty acids

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

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.

4

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

Glycogen phosphorylase . . . glucose-1-phosphate

Glycogen phosphorylase . . . glucose-6-phosphate

Glycogen phosphatase . . . glucose-1-phosphate

Glycogen phosphatase . . . glucose-6-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).

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