Question 1

Which of the following best describes a zwitterion at physiological pH?

Accepted Answer

A molecule with both a positive and a negative charge, resulting in an overall neutral charge.

Question 2

Which type of interaction is responsible for the formation of salt bridges in the tertiary structure of proteins?

Accepted Answer

Ionic attraction between acidic and basic amino acid side chains.

Question 3

What is the primary function of hemoglobin as classified in Table 19.1?

Accepted Answer

Transport essential substances throughout the body.

Question 4

Which of the following statements about enzyme activity is correct?

Accepted Answer

Enzyme activity increases with substrate concentration until all enzyme molecules are saturated.

Question 5

Which class of enzyme catalyzes the transfer of a functional group from one molecule to another?

Accepted Answer

Transferases

Question 6

A patient is given an antihistamine to treat allergy symptoms. What is the biochemical basis for the effectiveness of this drug?

Accepted Answer

It blocks histamine receptors, preventing histamine from triggering allergic responses.

Question 7

Which of the following best describes the secondary structure of a protein?

Accepted Answer

The arrangement of polypeptide chains into alpha helices and beta-pleated sheets stabilized by hydrogen bonds.

Question 8

Which of the following amino acids would most likely be found in the interior of a globular protein?

Accepted Answer

Leucine

Question 9

What is the effect of increasing temperature above 50°C on most human enzymes?

Accepted Answer

The enzyme denatures and loses its activity.

Question 10

Which of the following is a correct description of a peptide bond?

Accepted Answer

An amide bond formed between the carboxylate group of one amino acid and the ammonium group of another.

Question 11

Which of the following best explains why essential amino acids must be obtained from the diet?

Accepted Answer

The human body cannot synthesize them.

Question 12

A mutation causes a single amino acid substitution in the primary structure of a protein. Which level(s) of protein structure could be affected?

Accepted Answer

Primary, secondary, tertiary, and quaternary structures.

Question 13

Which of the following statements about amides is correct?

Accepted Answer

Amides are derivatives of carboxylic acids in which the hydroxyl group is replaced by an amine group.

Question 14

Which of the following is a function of contractile proteins?

Accepted Answer

Make muscles move

Question 15

Which of the following best describes the induced-fit model of enzyme action?

Accepted Answer

The enzyme's active site is flexible and adapts to fit the substrate.

Question 16

Which of the following is a correct example of a hydrophobic interaction in a protein's tertiary structure?

Accepted Answer

Nonpolar side chains clustering in the interior of the protein.

Question 17

Which of the following best explains why enzymes are highly specific for their substrates?

Accepted Answer

The active site of the enzyme has a unique shape and chemical environment that matches only specific substrates.

Question 18

Which of the following is a correct statement about the quaternary structure of proteins?

Accepted Answer

It involves the association of two or more polypeptide chains into a functional protein.

Question 19

Which of the following is a real-life example of protein denaturation?

Accepted Answer

Cooking an egg, which causes the egg white proteins to unfold and solidify.

Question 20

Which of the following best describes the effect of an enzyme on the activation energy of a reaction?

Accepted Answer

It lowers the activation energy, increasing the reaction rate.

Amines, Amides, Amino Acids, Proteins, and Enzymes: Structured Study Notes

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