Question 1

Which of the following statements about the structure of amino acids is CORRECT?

Accepted Answer

The alpha carbon of all amino acids is always attached to a hydrogen, a carboxyl group, an amino group, and a unique R group.

Question 2

Which amino acid is classified as 'basic' based on its side chain?

Accepted Answer

Lysine

Question 3

At physiological pH (around 7.4), what is the predominant form of a generic amino acid?

Accepted Answer

$$\mathrm{H_3N^+{-}CHR{-}COO^-}$$

Question 4

Which laboratory synthesis method for amino acids involves the use of phthalimide and diethyl bromomalonate?

Accepted Answer

Gabriel synthesis

Question 5

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

Accepted Answer

The pH at which the amino acid has no net electric charge.

Question 6

Which of the following best describes the peptide bond?

Accepted Answer

It is an amide bond formed between the carboxyl group of one amino acid and the amino group of another.

Question 7

Which enzyme cleaves peptide bonds on the carboxyl side of lysine and arginine residues?

Accepted Answer

Trypsin

Question 8

During Edman degradation, which amino acid is identified in each cycle?

Accepted Answer

The N-terminal amino acid

Question 9

Which of the following is a correct convention for writing peptide sequences?

Accepted Answer

From the N-terminus to the C-terminus

Question 10

Which property of the peptide bond gives rise to restricted rotation and partial double bond character?

Accepted Answer

Resonance between the carbonyl oxygen and the amide nitrogen

Question 11

A solution of alanine is titrated with NaOH. At the isoelectric point, which form of alanine predominates?

Accepted Answer

$$\mathrm{H_3N^+{-}CH(CH_3$){-}COO^-}$$

Question 12

Which of the following best explains why enzymes can catalyze reactions at physiological temperatures that would otherwise require high heat in the lab?

Accepted Answer

Enzymes stabilize the transition state, lowering the activation energy.

Question 13

Which of the following amino acids has a side chain that can form disulfide bonds?

Accepted Answer

Cysteine

Question 14

In the Strecker synthesis of amino acids, which intermediate is formed after the reaction of an imine with HCN?

Accepted Answer

An alpha-aminonitrile

Question 15

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

Accepted Answer

The overall three-dimensional folding of a single polypeptide chain

Question 16

Which of the following statements about the Hell-Volhard-Zelinsky reaction is TRUE in the context of amino acid synthesis?

Accepted Answer

It introduces a bromine atom at the alpha position of a carboxylic acid.

Question 17

Which analytical technique is used to determine the quantity and identity of amino acids after hydrolysis of a polypeptide?

Accepted Answer

Chromatography

Question 18

Which of the following is a consequence of the partial double bond character of the peptide bond?

Accepted Answer

The peptide bond is planar and restricts rotation.

Question 19

Which of the following amino acids is most likely to be found on the surface of a soluble protein?

Accepted Answer

Lysine

Amino Acids, Peptides, and Proteins: Structure, Properties, and Synthesis

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