Lecture 4: Amino Acids

Question 1

Good Rule of Thumb

Answer 1

At pH< pKa, protonated

At pH> pKa, deprotonated

Question 2

Properties of Amino Acids

Answer 2

Optically active

Engage in noncovalent interactions that determine protein structure/function

Question 3

Amino Acids are Optically Active

Answer 3

a-carbon is the chiral center of molecule

Only the L-configuration is found in proteins

Question 4

Polar, negative charged amino acids

Answer 4

Aspartate

Glutamate

Question 5

Polar, positive charged

Answer 5

Lysine, Arginine, Histidine

Question 6

Polar uncharged (-OH)

Answer 6

Serine, threonine, tyrosine

Question 7

Polar uncharged (Carboxamide- CONH2)

Answer 7

Asparagine, Glutamine

Question 8

Polar uncharged (-SH group)

Answer 8

Cysteine

Question 9

Nonpolar, aliphatic

Answer 9

Glycine, alanine
Branched: valine, leucine, isoleucine
Thioester: methionine
Ring structure; not aromatic: Proline

Question 10

Nonpolar, aromatic

Answer 10

Phenylalanine, tryptophan
Amphipathic: tyrosine
*Aromatic ring structure permits absorption of UV light (280 nm)

Question 11

Why is it important to know the classification and side chains/R-groups of amino acids?

Answer 11

Noncovalent interactions contribute to protein folding and reactivity