MCQs BIOCHEMISTRY: Structure of amino acids

1.
When the amino acid alanine (R-group is CH3) is added to a solution with a pH of 7.3, alanine becomes

A. a cation
B. nonpolar
C. a zwitterions
D. an isotope
Answer & Explanation
Answer: Option C

2.
What is the end product of leucine metabolism?

A. Acetyl-CoA
B. Pyruvic acid
C. Oxaloacetic acid
D. Acetyl carnitine
Answer & Explanation
Answer: Option A

3.
What is the heaviest of the twenty amino acids?

A. Phenylalanine B. Tryptophan
C. Tyrosine D. Histidine
Answer & Explanation
Answer: Option B

4.
Which of the following amino acids can form hydrogen bonds with their side (R) groups?

A. Asparagine
B. Aspartic acid
C. Glutamine
D. All of these
Answer & Explanation
Answer: Option D

5.
The isoelectric point of an amino acid is defined as the pH

A. where the molecule carries no electric charge
B. where the carboxyl group is uncharged
C. where the amino group is uncharged
D. of maximum electrolytic mobility
Answer & Explanation
Answer: Option A

6.
Molecules that bear charged groups of opposite polarity are known as

A. zwitterions
B. ambions
C. ion conversion
D. amphions
Answer & Explanation
Answer: Option A

7.
What is the product of the catabolic breakdown of Arginine?

A. Alpha-ketoglutarate B. Fumarate
C. Oxaloacetate D. Succinate
Answer & Explanation
Answer: Option A

8.
Which amino acids would most likely reside in the membrane-anchoring domain of a membrane embedded protein?

A. Isoleucine, valine and phenylalanine
B. Phenylalanine, valine, and aspartate
C. Leucine, threonine, and lysine
D. Lysine, arginine and histidine
Answer & Explanation
Answer: Option A

6.
Molecules that bear charged groups of opposite polarity are known as

A. zwitterions
B. ambions
C. ion conversion
D. amphions
Answer & Explanation
Answer: Option A

7.
What is the product of the catabolic breakdown of Arginine?

A. Alpha-ketoglutarate B. Fumarate
C. Oxaloacetate D. Succinate
Answer & Explanation
Answer: Option A

8.
Which amino acids would most likely reside in the membrane-anchoring domain of a membrane embedded protein?

A. Isoleucine, valine and phenylalanine
B. Phenylalanine, valine, and aspartate
C. Leucine, threonine, and lysine
D. Lysine, arginine and histidine
Answer & Explanation
Answer: Option A


9.
An essential amino acid is one that

A. is essentially easy to synthesize
B. is essential to flagella motion
C. the body cannot synthesize
D. the body can synthesize under essential conditions
Answer & Explanation
Answer: Option C

10.
D-Alanine and L-Alanine are technically known as

A. anomers B. enantiomers
C. epimers D. polymer
Answer & Explanation
Answer: Option B

11.
Which of the following pairs of amino acids would carry a negative charge on their side chain at pH 8.0?

A. Asparagine & Glutamine
B. Leucine & Glycine
C. Histidine & Lysine
D. Aspartate & Glutamate
Answer & Explanation
Answer: Option D

12.
In a polypeptide average mass of an amino acid residue is

A. 110 daltons
B. 118 daltons
C. 80 daltons
D. 150 daltons
Answer & Explanation
Answer: Option A

13.
Which pair of amino acids absorbs the most UV light at 280 nm?

A. Threonine & Histidine
B. Trp & Tyrosine
C. Cystein & Asparagine
D. Phenylalnine & Proline
Answer & Explanation
Answer: Option B

14.
Which of the following is a nonstandard amino acid?

A. Cysteine B. Isoleucine
C. Hydroxyproline D. Histidine
Answer & Explanation
Answer: Option C

15.
Which of the following is an essential amino acid?

A. Tryptophan
B. Methionine
C. Lysine
D. All of these
Answer & Explanation
Answer: Option D