Question 1

Which of the following best describes the general structure of an amino acid?

Accepted Answer

A central carbon atom bonded to a carboxyl group, an amino group, a hydrogen atom, and a variable R group.

Question 2

Which of the following is NOT one of the three categories that the 20 essential amino acids fall into?

Accepted Answer

Aromatic

Question 3

Proteins have directionality. Which terminus is synthesized first during translation?

Accepted Answer

N-terminus

Question 4

Formation of a peptide bond between two amino acids is an example of which type of reaction?

Accepted Answer

Dehydration synthesis

Question 5

Which equation best represents the formation of a peptide bond?

Accepted Answer

$$\mathrm{Amino\ acid}_1 + \mathrm{Amino\ acid}_2 \rightarrow \mathrm{Dipeptide} + H_2O$$

Question 6

Which of the following is a cardinal rule for being a protein?

Accepted Answer

Must have a specific three-dimensional structure

Question 7

Which force is primarily responsible for stabilizing the secondary structure of proteins such as alpha helices and beta sheets?

Accepted Answer

Hydrogen bonds

Question 8

Covalent modifications such as phosphorylation typically occur on which amino acid residues?

Accepted Answer

Serine, threonine, and tyrosine

Question 9

What is the primary function of molecular chaperones in the cell?

Accepted Answer

Assist in the proper folding of proteins

Question 10

Which of the following correctly lists the four levels of protein structure in order?

Accepted Answer

Primary, secondary, tertiary, quaternary

Question 11

Which statement best distinguishes a motif from a domain in protein structure?

Accepted Answer

A motif is a short, recurring structural element, while a domain is a larger, independently folding unit.

Question 12

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

Accepted Answer

Adenine

Question 13

Which of the following is a pyrimidine base found in DNA?

Accepted Answer

Thymine

Question 14

Which structural feature distinguishes purines from pyrimidines?

Accepted Answer

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

Question 15

Which of the following best describes the basic structure of a nucleotide?

Accepted Answer

A phosphate group, a five-carbon sugar, and a nitrogenous base

Question 16

Which of the following is true about the directionality of DNA?

Accepted Answer

DNA strands have directionality, with a 5' to 3' orientation.

Question 17

Which type of covalent bond is responsible for stabilizing the tertiary structure of proteins by linking cysteine residues?

Accepted Answer

Disulfide bond

Question 18

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

Accepted Answer

The protein may misfold or lose stability due to disruption of hydrophobic interactions.

Question 19

Which of the following best describes a beta sheet in protein secondary structure?

Accepted Answer

A structure formed by hydrogen bonds between backbone atoms of adjacent polypeptide chains, creating a sheet-like arrangement.

Question 20

Which of the following is an example of a covalent modification that regulates protein activity in cell signaling pathways?

Accepted Answer

Phosphorylation

Protein Structure, Amino Acids, and Nucleic Acids: Core Concepts for Cell Biology

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