Question 1

Which of the following best explains why there is restricted rotation around the peptide bond in proteins?

Accepted Answer

The peptide bond has partial double-bond character due to resonance between the carbonyl oxygen and the amide nitrogen.

Question 2

Which of the following is the correct chemical reaction for peptide bond formation between two amino acids?

Accepted Answer

$$\mathrm{R{-}COOH} + \mathrm{R'{-}NH_2$} \rightarrow \mathrm{R{-}CO{-}NH{-}R'} + \mathrm{H_2O}$$

Question 3

Which of the following statements about the primary structure of a protein is TRUE?

Accepted Answer

It is determined by the sequence of amino acids encoded by DNA.

Question 4

Which force is primarily responsible for stabilizing the alpha helix secondary structure in proteins?

Accepted Answer

Hydrogen bonds between the carbonyl oxygen of one amino acid and the amide hydrogen four residues ahead in the chain.

Question 5

A mutation changes a codon in the DNA sequence from GAA to GUA. What is the most direct effect on the protein produced?

Accepted Answer

The amino acid sequence will change, potentially altering the protein's primary structure.

Question 6

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

Accepted Answer

The assembly of multiple polypeptide chains into a functional protein complex.

Question 7

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

Accepted Answer

Proteins catalyze biochemical reactions as enzymes.

Question 8

Why is proline often referred to as a 'helix breaker' in protein secondary structure?

Accepted Answer

Proline's rigid ring structure restricts backbone rotation and disrupts the regular hydrogen bonding pattern of the alpha helix.

Question 9

Which of the following statements about beta sheets in proteins is CORRECT?

Accepted Answer

Beta sheets are stabilized by hydrogen bonds between backbone atoms of adjacent polypeptide strands.

Question 10

Which of the following best describes an amide functional group?

Accepted Answer

A nitrogen atom bonded to a carbonyl carbon and another carbon or hydrogen.

Question 11

Which of the following is a correct statement about the geometry of peptide bonds?

Accepted Answer

Peptide bonds are usually trans due to reduced steric hindrance between side chains.

Question 12

Which of the following is NOT a typical function of the tertiary structure of a protein?

Accepted Answer

Encoding the sequence of amino acids in the protein.

Question 13

A protein is found to have several alpha helices and beta sheets connected by loops. Which level of protein structure does this describe?

Accepted Answer

Secondary structure

Question 14

Which of the following interactions is most important for stabilizing the tertiary structure of a globular protein in water?

Accepted Answer

Hydrophobic interactions among nonpolar side chains

Question 15

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

Accepted Answer

It is synthesized from the N-terminus to the C-terminus.

Question 16

Which of the following is a consequence of the resonance structure of the peptide bond?

Accepted Answer

The peptide bond is planar and restricts rotation around the C-N axis.

Question 17

Which of the following is TRUE regarding the formation of a peptide bond?

Accepted Answer

It is a dehydration reaction that releases water.

Question 18

Which of the following is a real-life example of a protein's defense function?

Accepted Answer

Antibodies binding to pathogens in the immune system.

Question 19

Which of the following statements about protein folding is CORRECT?

Accepted Answer

Protein folding is influenced by the sequence of amino acids and interactions such as hydrogen bonds, ionic bonds, and hydrophobic effects.

Protein Structure and Function: Biochemistry Study Notes

Guida di studio - Domande di pratica