Question 1

Which of the following statements best describes the role of enzymes among the major classes of proteins in cells?

Accepted Answer

Enzymes serve as catalysts, increasing the rate of chemical reactions.

Question 2

A protein is found to have a high proportion of nonpolar amino acids in its core and charged amino acids on its surface. Which type of interaction is most responsible for stabilizing the protein's tertiary structure?

Accepted Answer

Hydrophobic interactions among nonpolar side chains

Question 3

Which covalent modification is most likely to permanently anchor a protein to a membrane?

Accepted Answer

Addition of a fatty acid to a cysteine residue (prenylation)

Question 4

A mutation changes a glycine residue in an alpha helix to a proline. What is the most likely effect on the protein's secondary structure?

Accepted Answer

The alpha helix will be disrupted, introducing a bend at the mutation site.

Question 5

Which of the following best explains why saturated fatty acids are solid at room temperature while unsaturated fatty acids are liquid?

Accepted Answer

Saturated fatty acids have straight chains that pack tightly, while unsaturated fatty acids have double bonds that create kinks, preventing tight packing.

Question 6

Which level of protein structure is directly determined by the sequence of nucleotides in messenger RNA?

Accepted Answer

Primary structure

Question 7

A scientist isolates a molecule with the formula $$C_6H_{12}O_6$. Which class of macromolecule is this most likely a monomer for?

Accepted Answer

Polysaccharides

Question 8

Which of the following bonds is responsible for linking nucleotides together in a DNA strand?

Accepted Answer

3',5' phosphodiester bond

Question 9

A patient is diagnosed with a genetic disorder that affects the formation of disulfide bonds in proteins. Which amino acid is most likely mutated in this patient?

Accepted Answer

Cysteine

Question 10

Which of the following is a function of glycosylation as a covalent modification of proteins?

Accepted Answer

Increasing protein polarity and enabling new interactions

Question 11

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

Accepted Answer

The association of multiple polypeptide subunits into a functional complex

Question 12

Which of the following is TRUE regarding the structure of DNA?

Accepted Answer

DNA is a double-stranded helix with deoxyribose as its sugar.

Question 13

A cell is exposed to a high salt concentration. Which of the following is most likely to occur to its proteins?

Accepted Answer

Proteins may denature due to disruption of ionic bonds and interactions.

Question 14

Which of the following is a major difference between phosphoglycerides and sphingolipids in membranes?

Accepted Answer

Phosphoglycerides have a glycerol backbone, while sphingolipids have a sphingosine backbone.

Question 15

Which of the following is the correct order of protein structural organization from simplest to most complex?

Accepted Answer

Primary, secondary, tertiary, quaternary

Question 16

A researcher discovers a new protein that is able to switch between two stable shapes in response to changes in pH. What property of proteins does this illustrate?

Accepted Answer

Proteins can be activated and inactivated by subtle changes in conformation.

Question 17

Which of the following is a function of cholesterol in animal cell membranes?

Accepted Answer

It modulates membrane fluidity and serves as a precursor for steroid hormones.

Question 18

Which of the following best describes the formation of a glycosidic bond in a disaccharide?

Accepted Answer

It is formed by the elimination of water between two monosaccharides.

Question 19

A patient is unable to digest cellulose but can digest starch. What is the most likely explanation for this difference?

Accepted Answer

Cellulose contains beta(1-4) glycosidic bonds, which human enzymes cannot break, while starch contains alpha(1-4) bonds, which can be digested.

Chapter 3: The Macromolecules of the Cell – Structure, Function, and Types

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