Question 1

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

Accepted Answer

The sequence of amino acids linked by peptide bonds

Question 2

A mutation causes a single amino acid substitution in a protein. Which level of protein structure is directly affected first?

Accepted Answer

Primary structure

Question 3

Hydrogen bonds between the backbone atoms of a polypeptide are most important in stabilizing which level of protein structure?

Accepted Answer

Secondary structure

Question 4

Which of the following interactions is responsible for the formation of disulfide bridges in proteins?

Accepted Answer

Covalent bonds between cysteine side chains

Question 5

A protein is denatured by heat, causing it to lose its function. Which level(s) of structure are most likely disrupted?

Accepted Answer

Secondary, tertiary, and quaternary structures

Question 6

Which of the following best explains why sickle cell anemia occurs at the molecular level?

Accepted Answer

A single amino acid substitution alters the primary structure, affecting the protein's shape and function

Question 7

Which of the following statements about nucleic acids is correct?

Accepted Answer

Phosphodiester bonds link nucleotides together in a strand

Question 8

What is the main structural difference between ribose and deoxyribose sugars in nucleic acids?

Accepted Answer

Ribose has a hydroxyl group ($$-OH) at $$the 2' carbon, while deoxyribose has a hydrogen ($$-H) at $$the 2' carbon

Question 9

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

Accepted Answer

The association of multiple folded polypeptide subunits to form a functional protein

Question 10

A scientist is studying a protein that consists of two identical polypeptide chains. Which level of protein structure is directly involved in holding these chains together?

Accepted Answer

Quaternary structure

Question 11

Which of the following is a correct description of the backbone of a polypeptide chain?

Accepted Answer

A repeating sequence of $$-N-C-C-$$ atoms from the amino and carboxyl groups of amino acids

Question 12

In DNA, the two strands are held together by which type of bond between nitrogenous bases?

Accepted Answer

Hydrogen bonds

Question 13

Which of the following best explains why proteins can have such diverse functions in cells?

Accepted Answer

The variety of amino acid side chains and the complexity of folding allow for a wide range of shapes and chemical properties

Question 14

A researcher finds that a protein is unable to form alpha helices or beta sheets. Which level of structure is most likely disrupted?

Accepted Answer

Secondary structure

Question 15

Which of the following is true regarding the directionality of nucleic acid strands?

Accepted Answer

Nucleic acid strands have a 5' to 3' direction, determined by the sugar-phosphate backbone

Question 16

Which of the following best describes the role of hydrophobic interactions in protein folding?

Accepted Answer

They cause nonpolar side chains to cluster away from water, stabilizing the protein's tertiary structure

Question 17

A patient has a genetic disorder that prevents the formation of phosphodiester bonds. Which biological molecule would be most directly affected?

Accepted Answer

DNA and RNA

Question 18

Which of the following is a correct statement about the difference between DNA and RNA?

Accepted Answer

DNA contains deoxyribose sugar, while RNA contains ribose sugar

Question 19

Which of the following best explains why a change in pH can denature a protein?

Accepted Answer

A change in pH alters the charges on amino acid side chains, disrupting ionic and hydrogen bonds that stabilize the protein's structure

Question 20

A protein is composed of four polypeptide subunits. If one subunit is mutated and cannot bind to the others, which level of structure is most directly affected?

Accepted Answer

Quaternary structure

UNIT 1: Review of Proteins and Nucleic Acids: Structure and Function

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