Question 1

Which type of bond links amino acids together to form the primary structure of a protein?

Accepted Answer

Peptide bond

Question 2

A mutation changes the sequence of amino acids in a protein but does not affect the peptide bonds. Which level of protein structure is directly altered?

Accepted Answer

Primary structure

Question 3

Given the peptide sequence Ala-Gly-Ser, which of the following best represents the directionality of the primary structure?

Accepted Answer

From the N-terminus to the C-terminus

Question 4

Which of the following statements about the primary structure of proteins is CORRECT?

Accepted Answer

It determines the three-dimensional folding of the protein.

Question 5

A new drug cleaves peptide bonds in a polypeptide chain. Which level of protein structure is most directly affected?

Accepted Answer

Primary structure

Question 6

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

Accepted Answer

The sequence of amino acids linked by peptide bonds

Question 7

If a peptide has the sequence Lys-Ala-Gly, which amino acid is at the N-terminus?

Accepted Answer

Lysine

Question 8

Which of the following is TRUE regarding the effect of altering the primary structure of a protein?

Accepted Answer

It can change the protein's folding and function.

Question 9

A peptide is found to be an effective buffer at pH 10. Which amino acid residue is most likely responsible for this property?

Accepted Answer

Tyrosine

Question 10

Which of the following best explains why the sequence of amino acids in a protein is important?

Accepted Answer

It dictates the protein's final three-dimensional structure and function.

Question 11

Which of the following is the correct general formula for a peptide bond formation between two amino acids?

Accepted Answer

$$\mathrm{R_1$-CH(NH_2$)-COOH + R_2$-CH(NH_2$)-COOH \rightarrow R_1$-CH(NH_2$)-CO-NH-CH(R_2$)-COOH + H_2O}$$

Question 12

Which of the following would NOT alter the primary structure of a protein?

Accepted Answer

Denaturation by heat

Question 13

Which of the following best describes the relationship between the primary structure and the function of a protein such as Angiotensin I Converting Enzyme (ACE)?

Accepted Answer

The primary structure determines the enzyme's specificity and activity.

Question 14

Which of the following is a direct consequence of altering the sequence of amino acids in the primary structure of a protein?

Accepted Answer

The protein may fold incorrectly, leading to loss of function.

Question 15

Which of the following is the correct order of levels of protein structure from simplest to most complex?

Accepted Answer

Primary $$\rightarrow$$ Secondary $$\rightarrow$$ Tertiary $$\rightarrow$$ Quaternary

Question 16

Which of the following best describes the N-terminus of a polypeptide?

Accepted Answer

The end with a free amino group

Question 17

A peptide contains the sequence Phe-Gly-Ser-Tyr. Which residue is most likely to contribute to the peptide's ability to absorb UV light at 280 nm?

Accepted Answer

Tyrosine

Question 18

Which of the following is TRUE regarding the effect of a protease on a protein?

Accepted Answer

It hydrolyzes peptide bonds, disrupting the primary structure.

Question 19

Which of the following amino acids is most likely to be found at the C-terminus of a peptide with a net negative charge at physiological pH?

Accepted Answer

Aspartic acid

Question 20

Which of the following best explains why the primary structure of a protein is unique for each protein?

Accepted Answer

It is determined by the sequence of nucleotides in the gene encoding the protein.

Primary Structure of Proteins: Composition, Sequence, and Biological Importance

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