Question 1

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

Accepted Answer

The sequence of amino acids in a polypeptide chain, held together by peptide bonds ($	ext{Primary structure} = 	ext{amino acid sequence}$)

Question 2

A mutation changes a hydrophobic amino acid to a hydrophilic one in the core of a protein. What is the most likely effect on the protein's structure?

Accepted Answer

The protein may misfold or become unstable due to disruption of hydrophobic interactions in the core

Question 3

Which type of bond is primarily responsible for stabilizing the secondary structure of proteins?

Accepted Answer

Hydrogen bonds between the backbone amide and carbonyl groups

Question 4

A protein exposed to high temperature and extreme pH loses its function. What is the most likely explanation for this loss?

Accepted Answer

Denaturation has disrupted the protein's three-dimensional structure, altering its active site

Question 5

Which of the following amino acids contains a sulfur atom that can form a covalent disulfide bridge?

Accepted Answer

Cysteine ($\ce{Cys}$ or $\ce{C}$)

Question 6

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

Accepted Answer

A single amino acid substitution (valine for glutamic acid) in the primary structure of hemoglobin alters its shape and function

Question 7

Which of the following statements about peptide bonds is correct?

Accepted Answer

A peptide bond forms between the carboxyl group of one amino acid and the amino group of another, releasing water ($\ce{C-N}$ bond, dehydration synthesis)

Question 8

Which of the following is a function of defensive proteins in the human body?

Accepted Answer

Antibodies bind to and help neutralize pathogens such as bacteria and viruses

Question 9

A scientist is studying a protein that consists of four polypeptide chains. Which level of protein structure is directly involved in the arrangement of these chains?

Accepted Answer

Quaternary structure

Question 10

Which of the following best describes the difference between a polypeptide and a functional protein?

Accepted Answer

A polypeptide is a linear chain of amino acids, while a functional protein is one or more polypeptides folded into a specific three-dimensional shape

Question 11

Which of the following amino acids would most likely be found on the exterior of a soluble protein in an aqueous environment?

Accepted Answer

Asparagine ($\ce{Asn}$ or $\ce{N}$), which has a polar side chain

Question 12

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

Accepted Answer

A repeating sequence of $-\ce{N}-\ce{C}_\alpha-\ce{C}- $ atoms, excluding the side chains (R groups)

Question 13

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

Accepted Answer

Phosphodiester bonds between nucleotides

Question 14

Which of the following best explains why proteins can perform such a wide variety of functions in living organisms?

Accepted Answer

Proteins are made from 20 different amino acids, allowing for diverse sequences and complex three-dimensional structures

Question 15

Which of the following is a correct statement about the directionality of nucleic acids?

Accepted Answer

Nucleic acids have a 5' end with a phosphate group and a 3' end with a hydroxyl group

Question 16

Which of the following best describes the structure of DNA?

Accepted Answer

A double helix with two antiparallel strands held together by hydrogen bonds between complementary bases

Question 17

Which of the following base pairs is correct according to the rules of complementary base pairing in DNA?

Accepted Answer

Adenine pairs with Thymine ($\ce{A} - \ce{T}$) via two hydrogen bonds

Question 18

Which of the following is a difference between purines and pyrimidines?

Accepted Answer

Purines have a double-ring structure, while pyrimidines have a single-ring structure

Question 19

A researcher is analyzing a nucleic acid and finds it contains uracil but not thymine. Which type of nucleic acid is it most likely to be?

Accepted Answer

RNA

Chapter 5: Macromolecules – Proteins and Nucleic Acids

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