Chapter 4 Multiple Choice Questions

. Which of the following fibres does NOT contain protein?

Human hair

Cotton fibres

Tendons

Spider silk

. Enzymes are biological molecules that catalyse reactions. They can be all except one of the following; that is, which type of molecule is NOT known to have catalytic activity?

RNA molecules

DNA molecules

Polysaccharides proteins

Proteins

. A competitive inhibitor blocks enzyme action by

necessarily causing a conformational change in the enzyme that destroys its catalytic activity.

hydrolyzing the polypeptide chain of the enzyme.

denaturing the enzyme.

binding to the active site but being unable to undergo the reaction.

. According to the Michaelis-Menten model, the kinetic properties of an enzyme are characterized by the Michaelis constant K_M and the maximum velocity V_max. Which of the following is true? In the presence of a competitive inhibitor

K_M will change but V_max will not change.

both K_M and V_max will be unchanged.

both K_M and V_max will change.

K_M will not change but V_max will change.

. The complementarity-determining regions of an antibody (= the antigen-binding site) appear

in the variable domains of light chains only.

in the constant domains of heavy chains.

in the variable domains of heavy and light chains.

in the constant domains of light chains.

. Transfer of an ion across a membrane from a region of high concentration on one side of the membrane to a region of low concentration on the other side of the membrane

requires coupling to hydrolysis of ATP.

will bring the relative concentrations of the ion on the two sides of the membrane farther from equilibrium.

can never be coupled to synthesis of ATP.

will take place spontaneously without hydrolysis of ATP.

. Many proteins that sit in the outer membrane of a cell bind a signalling molecule, and trigger intracellular processes as a result of receipt of the signal. For this to happen

the signalling molecule must enter the cell and interact with intracellular proteins.

the signalling molecule can trigger an activating conformational change in the receptor that activates a process within the cell, without the signalling molecules entering the cell.

in order to affect gene expression the signalling molecule must enter not only the cell, but the nucleus.

once the signal is received the signalling molecule is in all cases destroyed.

. The Enzyme Commission (EC) and Gene Ontology Consortium (GO) both have created catalogues of protein function. Which of the following is true?

The Gene Ontology Consortium catalogue is limited to enzymatic functions.

The Enzyme Commission catalogue contains more categories than the Gene Ontology Consortium catalogue.

The Gene Ontology Consortium catalogue contains more categories than the Enzyme Commission catalogue.

Both the Enzyme Commission catalogue and the Gene Ontology Consortium catalogue classify the functions of individual proteins; for instance, they assign an enzymatic function to yeast hexokinase, an enzyme that phosphorylates glucose.

. Which of the following is NOT a category of the Gene Ontology Consortium?

Cellular component

Chromosomal location of protein-coding genes

Biological process

Molecular function

. Escherischia coli and Methanococcus jannischii both have enzymes that phosphorylate shikimic acid, in the pathway of aromatic amino-acid biosynthesis. These enzymes are unrelated; they have the same function but completely different structure. Which of the following is true?

The activities of the two enzymes would be classified differently in the Enzyme Commission catalogue.

The activity of the E. coli enzyme would be classified in the Enzyme Commission catalogue but not in the Gene Ontology Consortium catalogue.

The activities of the two enzymes would be classified differently in the Gene Ontology Consortium catalogue.

The activities of the two enzymes would have the same classification in the Enzyme Commission catalogue.

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