Question 1

Which of the following statements best describes a zwitterion form of an amino acid at physiological pH?

Accepted Answer

It has a positively charged amino group and a negatively charged carboxyl group.

Question 2

Which amino acid is NOT a primary amine?

Accepted Answer

Proline

Question 3

Amino acids are classified based on the properties of their side chains. Which of the following amino acids contains an aromatic ring in its side chain?

Accepted Answer

Phenylalanine

Question 4

Which of the following best explains why humans require essential amino acids in their diet?

Accepted Answer

Essential amino acids cannot be synthesized by the body.

Question 5

What is the chemical reaction used to detect amino acids in fingerprints, producing a deep blue or purple color?

Accepted Answer

Ninhydrin reaction

Question 6

Which of the following is TRUE about enantiomers of amino acids?

Accepted Answer

They have identical chemical properties but differ in the direction they rotate plane-polarized light.

Question 7

A mixture containing equal amounts of L- and D- forms of an amino acid is called:

Accepted Answer

A racemic mixture

Question 8

Which of the following equations correctly represents the isoelectric point ($pI$) of a simple amino acid with only two ionizable groups?

Accepted Answer

$pI = \frac{pK_a + pK_b}{2}$

Question 9

Which of the following amino acids has a side chain that can form disulfide bonds, contributing to protein structure stabilization?

Accepted Answer

Cysteine

Question 10

If a protein is hydrolyzed, which type of bond is broken to release individual amino acids?

Accepted Answer

Peptide (amide) bond

Question 11

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

Accepted Answer

A peptide is a short chain of amino acids, while a polypeptide is a long, continuous, and unbranched chain.

Question 12

Which of the following amino acids is classified as non-polar and aliphatic?

Accepted Answer

Valine

Question 13

Which post-translational modification introduces a phosphate group to an amino acid side chain?

Accepted Answer

Phosphorylation

Question 14

Which of the following is a correct statement about the storage of amino acids in the human body?

Accepted Answer

Amino acids cannot be stored in the body like fat.

Question 15

Which of the following is a consequence of a low protein diet in humans?

Accepted Answer

Protein synthesis slows in the body.

Question 16

Which of the following amino acids is positively charged at physiological pH?

Accepted Answer

Lysine

Question 17

Which of the following is a property of chiral amino acids?

Accepted Answer

They exist as non-superimposable mirror images.

Question 18

Which of the following is the correct general structure of an alpha-amino acid in its zwitterionic form?

Accepted Answer

$NH_3^+ - CH(R) - COO^-$

Question 19

Which laboratory technique utilizes the ninhydrin reaction to detect amino acids?

Accepted Answer

Detection of fingerprints

Question 20

Which of the following statements about the stereospecificity of enzymes is correct?

Accepted Answer

Enzymes are stereospecific due to the asymmetric nature of their active sites.

Amino Acids: Structure, Classification, and Biochemical Properties

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