Question 1

Which of the following amino acids is an essential amino acid in the diets of children but not adults?

Accepted Answer

Arginine is considered an essential amino acid in children because their bodies cannot produce enough to meet their needs for growth and development, whereas adults can usually synthesize sufficient amounts.

Question 2

How many amino acids are essential in humans?

Accepted Answer

Humans require 10 essential amino acids that the body cannot synthesize on its own and must be obtained from the diet.

Question 3

What type of amino acid is phenylalanine?

Accepted Answer

Phenylalanine is a nonpolar, neutral amino acid due to its hydrophobic benzyl side chain, which does not interact favorably with water.

Question 4

What type of amino acid is tyrosine?

Accepted Answer

Tyrosine is a polar neutral amino acid because it contains a hydroxyl group (-OH) in its side chain, which can form hydrogen bonds, making it polar, but it does not carry a charge at physiological pH, making it neutral.

Question 5

What type of amino acid is glutamic acid?

Accepted Answer

Glutamic acid is an acidic amino acid due to the presence of a carboxylic acid group in its side chain, which can donate a proton (H+), making the environment more acidic.

Question 6

What type of amino acid is histidine?

Accepted Answer

Histidine is considered a basic amino acid due to the presence of an imidazole group in its side chain, which can accept a proton under physiological conditions.

Question 7

What are the three letter and one letter designation for tyrosine?

Accepted Answer

Tyrosine is represented by the three-letter code Tyr and the one-letter code Y.

Question 8

What are the three letter and one letter designation for asparagine?

Accepted Answer

Asparagine is denoted by the three-letter code Asn and the one-letter code N.

Question 9

What are the three letter and one letter designation for aspartate?

Accepted Answer

Aspartate is denoted by the three-letter code Asp and the one-letter code D.

Question 10

Which of the following amino acids contains sulfur in the side chain?

Accepted Answer

Cysteine contains sulfur in its side chain, which distinguishes it from the other amino acids listed.

Question 11

Which of the following amino acids contains an aromatic ring in the side chain?

Accepted Answer

Tryptophan contains an indole ring, which is an aromatic structure, in its side chain.

Question 12

All amino acids contain a chiral carbon except for one. Which one?

Accepted Answer

Glycine is the only amino acid that does not contain a chiral carbon because it has two hydrogen atoms attached to its alpha carbon, making it achiral.

Question 13

Which of the following amino acids is classified as being hydrophobic?

Accepted Answer

Phenylalanine is classified as hydrophobic due to its benzyl side chain, which tends to avoid water and prefers to be in non-polar environments.

Question 14

Which of the following amino acids is classified as being hydrophilic?

Accepted Answer

Aspartate is classified as hydrophilic due to its polar side chain, which can form hydrogen bonds with water, making it soluble in aqueous environments.

Question 15

Which list contains only nonpolar amino acids?

Accepted Answer

Nonpolar amino acids are characterized by their hydrophobic side chains. Glycine (Gly), Leucine (Leu), Isoleucine (Ile), and Phenylalanine (Phe) all have hydrophobic side chains, making them nonpolar.

Question 16

Which list contains only neutral polar amino acids?

Accepted Answer

Neutral polar amino acids have side chains that are polar but do not carry a charge at physiological pH. Asn (Asparagine), Gln (Glutamine), Cys (Cysteine), and Tyr (Tyrosine) fit this description.

Question 17

Which list contains only essential amino acids?

Accepted Answer

C) His, Lys, Trp, Ile are all essential amino acids, meaning they cannot be synthesized by the human body and must be obtained from the diet.

Question 18

An essential amino acid is defined as one that:

Accepted Answer

Essential amino acids are those that cannot be synthesized by the human body and therefore must be obtained from the diet.

Question 19

Corn is an incomplete protein because it lacks one or more:

Accepted Answer

Corn is considered an incomplete protein because it lacks one or more essential amino acids, which are amino acids that the body cannot synthesize on its own and must obtain from the diet.

Question 20

Which is not a characteristic element of proteins?

Accepted Answer

Proteins are primarily composed of carbon (C), hydrogen (H), and nitrogen (N), along with oxygen and sometimes sulfur, but chlorine (Cl) is not a characteristic element of proteins.

Quiz 10: Proteins - Workers of the Cell