Question 1

Which of the following statements best describes the primary structure of a protein?

Accepted Answer

It is the sequence of amino acids joined by peptide bonds.

Question 2

At physiological pH, what is the net charge of glycine?

Accepted Answer

Zero (zwitterion)

Question 3

Which type of interaction is responsible for the formation of a disulfide bond in the tertiary structure of a protein?

Accepted Answer

Disulfide bond between two cysteine residues

Question 4

Which amino acid would you expect to find on the inside of a folded protein, away from water?

Accepted Answer

Valine

Question 5

A competitive inhibitor of an enzyme:

Accepted Answer

Has a structure similar to the substrate and competes for the active site.

Question 6

Which of the following is an example of a protein with quaternary structure?

Accepted Answer

Hemoglobin

Question 7

What is the effect of increasing the temperature above the optimum for an enzyme-catalyzed reaction?

Accepted Answer

The enzyme activity decreases due to denaturation.

Question 8

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

Accepted Answer

Transferase

Question 9

A patient with sickle-cell anemia has a mutation in hemoglobin where glutamic acid is replaced by valine. What is the consequence of this substitution?

Accepted Answer

Hydrophobic interactions cause hemoglobin molecules to stick together, forming fibers.

Question 10

Which of the following amino acids is classified as basic at physiological pH?

Accepted Answer

Lysine

Question 11

Which statement about enzyme-substrate binding in the induced-fit model is correct?

Accepted Answer

The enzyme and substrate both change shape for optimal binding.

Question 12

Which of the following is true about essential amino acids?

Accepted Answer

They must be obtained from dietary proteins.

Question 13

What type of secondary structure is formed by hydrogen bonds between the carbonyl oxygen and amide hydrogen atoms in adjacent polypeptide chains?

Accepted Answer

Beta-pleated sheet

Question 14

Which of the following would most likely cause denaturation of a protein?

Accepted Answer

Heating the protein above 60°C

Question 15

Which of the following is the correct formula for the isoelectric point ($$pI) of $$glycine?

Accepted Answer

$$pI = \frac{pK_{a,COOH} + pK_{a,NH_3$^+}}{2}$$

Question 16

Which enzyme class catalyzes the hydrolysis of lipids?

Accepted Answer

Hydrolase

Question 17

A noncompetitive inhibitor differs from a competitive inhibitor because:

Accepted Answer

It binds to a site other than the active site and cannot be reversed by increasing substrate concentration.

Question 18

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

Accepted Answer

The active site contains amino acid R groups that interact specifically with the substrate.

Question 19

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

Accepted Answer

The hardening of an egg when boiled

Question 20

Which of the following amino acids would have a net charge of +2 at low pH?

Accepted Answer

Arginine

CHAPTER 16 : Amino Acids and Proteins: Structure, Classification, and Biological Functions

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