Question 1

Which of the following statements best describes the role of amino acids in proteins?

Accepted Answer

Amino acids are the building blocks of proteins and contribute to their diverse functions such as defense, movement, signaling, structure, and transport.

Question 2

At physiological pH, what is the predominant form of the carboxyl and amino groups in an amino acid?

Accepted Answer

The carboxyl group is dissociated ($$-COO^-) $$and the amino group is protonated ($$-NH_3$^+).$$

Question 3

Which type of bond is formed between the carboxyl group of one amino acid and the amino group of another during protein synthesis?

Accepted Answer

Peptide bond

Question 4

Amino acids can be classified based on the properties of their side chains (R-groups). Which of the following is NOT a correct classification?

Accepted Answer

Aromatic

Question 5

Which amino acid contains a sulfhydryl (thiol) group and can form disulfide bonds important for protein structure?

Accepted Answer

Cysteine

Question 6

What is the Henderson-Hasselbalch equation used for in biochemistry?

Accepted Answer

To determine the relationship between the pH of a solution and the concentration of a weak acid and its conjugate base.

Question 7

Given the Henderson-Hasselbalch equation $$pH = pK_a + \log \left( \frac{[A^-]}{[HA]} \right)$$, what happens to the ratio $$\frac{[A^-]}{[HA]}$$ when the pH equals the $$pK_a$$?

Accepted Answer

The ratio is 1.

Question 8

Which property of amino acids allows them to act as buffers in biological systems?

Accepted Answer

Their amphoteric nature, having both acidic and basic groups.

Question 9

Which of the following amino acids is NOT chiral?

Accepted Answer

Glycine

Question 10

A patient’s blood pH is measured at 7.1. If the $$pK_a of $$the bicarbonate buffer system is 6.1, and the ratio $$\frac{[$$HCO_3$$^-]}{[H_2CO_3]} is 10$$, what is the calculated pH using the Henderson-Hasselbalch equation?

Accepted Answer

$$pH = 6.1 + \log(10) = 7.1$$

Question 11

Which amino acid is most likely to be found on the exterior of a soluble protein in an aqueous environment?

Accepted Answer

Serine

Question 12

What is the isoelectric point (pI) of an amino acid?

Accepted Answer

The pH at which the amino acid has a net charge of zero.

Question 13

Which of the following amino acids can serve as a site for oligosaccharide attachment in glycoproteins?

Accepted Answer

Asparagine

Question 14

Which amino acid is commonly found in the structure of collagen and disrupts alpha-helices in proteins due to its cyclic structure?

Accepted Answer

Proline

Question 15

At physiological pH, which amino acids have side chains that are fully ionized and negatively charged?

Accepted Answer

Aspartate and Glutamate

Question 16

Which amino acid is weakly basic and has buffering capabilities near physiological pH?

Accepted Answer

Histidine

Question 17

Which statement about the D- and L-isomers of amino acids is correct?

Accepted Answer

Only L-isomers are found in mammalian proteins; D-isomers are found in some antibiotics and bacterial cell walls.

Question 18

Which of the following best explains why nonpolar amino acids tend to cluster together in the interior of soluble proteins?

Accepted Answer

They are hydrophobic and avoid interaction with water, resulting in the hydrophobic effect.

Question 19

A solution contains alanine at a pH equal to its pI. What is the net charge of alanine in this solution?

Accepted Answer

0

Introduction to Amino Acids and Their Biochemical Properties

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