Q: Which of the following best describes the flow of genetic information in a cell?

$$\text{DNA} \rightarrow \text{mRNA} \rightarrow \text{Protein}$$

Question 1

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

Accepted Answer

The unique linear sequence of amino acids joined by peptide bonds, from the N-terminus to the C-terminus.

Question 2

A mutation causes the substitution of a nonpolar amino acid for a charged amino acid in the active site of an enzyme. Which level(s) of protein structure could be directly affected?

Accepted Answer

Primary, tertiary, and possibly quaternary structure.

Question 3

Which of the following amino acids has a side chain that can form a disulfide bond, contributing to tertiary structure?

Accepted Answer

Cysteine

Question 4

What type of bond links nucleotides together in a single strand of DNA or RNA?

Accepted Answer

Phosphodiester bond

Question 5

Which of the following best explains why heating an egg causes the egg white to turn from clear to opaque?

Accepted Answer

Heat causes denaturation of egg white proteins, disrupting their secondary and tertiary structures.

Question 6

Which of the following statements about DNA and RNA is correct?

Accepted Answer

DNA contains deoxyribose, while RNA contains ribose.

Question 7

Which of the following base pairs is found in DNA but not in RNA?

Accepted Answer

Adenine–Thymine

Question 8

A scientist isolates a nucleic acid and finds that it contains the sugar ribose, the bases adenine, guanine, cytosine, and uracil, and is single-stranded. What type of molecule is this?

Accepted Answer

RNA

Question 9

Which of the following best describes the flow of genetic information in a cell?

Accepted Answer

$$	ext{DNA} ightarrow 	ext{mRNA} ightarrow 	ext{Protein}$$

Question 10

Which of the following is a consequence of a single amino acid substitution in the primary structure of hemoglobin, as seen in sickle-cell anemia?

Accepted Answer

It can alter the protein's tertiary and quaternary structure, leading to loss of normal function.

Question 11

Which of the following best describes the difference between a nucleoside and a nucleotide?

Accepted Answer

A nucleotide contains a phosphate group, while a nucleoside does not.

Question 12

Which of the following amino acids is classified as acidic and negatively charged at physiological pH?

Accepted Answer

Glutamic acid

Question 13

What is the main function of chaperonin proteins in the cell?

Accepted Answer

They assist in the proper folding of other proteins.

Question 14

Which of the following best explains why a denatured protein is usually biologically inactive?

Accepted Answer

Denaturation disrupts the protein's three-dimensional structure, preventing it from performing its function.

Question 15

Which of the following statements about the directionality of nucleic acids is correct?

Accepted Answer

Nucleic acids are synthesized in the 5′ to 3′ direction, with new nucleotides added to the 3′ OH group.

Question 16

Which of the following interactions is NOT involved in stabilizing the tertiary structure of a protein?

Accepted Answer

Peptide bonds between amino acids

Question 17

Which of the following best describes the backbone of a polynucleotide chain?

Accepted Answer

It consists of alternating sugar and phosphate groups linked by phosphodiester bonds.

Question 18

Which of the following is a purine base found in both DNA and RNA?

Accepted Answer

Adenine

Question 19

A protein is exposed to a solution with a very high salt concentration. What is the most likely effect on the protein?

Accepted Answer

The protein may denature due to disruption of ionic bonds and other interactions.

LEC 4: Proteins and Nucleic Acids: Structure and Function

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