Amino Acids

Question 1

Which of the 20 essential amino acids is technically an imino acid?

Answer 1

Proline

Question 2

Which of the 20 essential amino acids are not chiral?

Answer 2

Glycine. Has two H groups

Question 3

Where might you find the d form of amino acids?

Answer 3

In bacterial cell walls

In some antibiotics

Question 4

Which amino acid is highly reactive and forms disulfide bonds with other residues of the same type?

Answer 4

Cysteine

Question 5

Why is proline conformationally rigid?

Answer 5

Its side chain is bound back on to its amino group

Question 6

The side chains of alanine, leucine, valine and methionine are _ and _

Answer 6

Hydrophobic

Aliphatic

Question 7

Which three amino acids are hydrophhobic by virtue of their aromaticity?

Answer 7

Tryptophan, Phenylalanine and Tyrosine

Question 8

Which two amino acids have positively charged side chains at neutral pH (always)?

Answer 8

Arginine and Lysine

Question 9

Which amino acid can be positively charged or neutral at neutral pH?

Answer 9

Histidine

Question 10

Which two amino acids possess a negative charge? Which group is repsonsible?

Answer 10

Aspartic acid
Glutamic acid

Carboxyl group

Question 11

Asparagine and Glutamine are _ and _

They can _

Answer 11

Polar
Uncharged

Participate in hydrogen bonding

Question 12

Which two amino acids are polar due to hydroxyl groups, and participate in hydrogen bonding?

Answer 12

Serine and Threonine

Question 13

In helathy individuals, the pH of blood is controlled at a value of

Answer 13

7.4

Question 14

The major buffering components in biological fluids are

Answer 14

Carbonate and Phosphate ions

Question 15

Amino acids are effective buffers, helping to keep pH in the physiological range _

Answer 15

6-8

Question 16

Why is it necessary to use a buffered solution when working with enzymes/proteins?

Answer 16

To avoid denaturation (loss of activity)

Question 17

Give an example of a buffer commonly used in the lab

Answer 17

Tris

Question 18

Which category of amino acids have 3 acid-base groups?

Answer 18

Ones with ionizable side chains

Question 19

On a titration curve, as pH increases, you can discriminate distinct points representing _

Answer 19

The dissociation of specific groups on amino acids

Question 20

The pH at which it has no net charge is termed _

Answer 20

The isoelectric point pI

Question 21

Which groups have pK values in the range of 1.8 to 2.5?

Answer 21

Alpha carboxyl

Question 22

Which groups have pK values in the range of 8.7 to 10.7?

Answer 22

Alpha amino

Question 23

Which groups are free to ionize in proteins?

Answer 23

Side chains

The terminal alpha carboxyl and amino groups