Nutrition Quiz 3

Dipeptide

2 AA

Tripeptide

3 AA

Oligopeptide

3-30 AA

Peptide

less than 50 AA

Protein

Over 50 AA

What makes up an AA?

Amine group, carboxyl group, chiral carbon (D vs. L), R group

Which Chiral center is active?

L

Which chiral center is inactive?

D

Characteristics of AA

Zwitterions - no net charge, charges cancel out

What determines identities of AA?

R group

Aliphatic essential AA

Isoleucine, Leucine, Valine

Hydroxyl essential AA

Threonine

Sulfur essential AA

Methionine

Acidic essential AA + their amides

none!

Basic essential AA

ALL: arginine, lysine, histidine

Aromatic essential AA

Histidine, Phenylalanine, tryptophan

Imino essential AA

none!

Characteristics of aliphatic AA

Added C’s and H’s

Characteristics of hydroxyl AA

Added -OH

Characteristics of Sulfur AA

Added -S

Characteristics of Acidic AA + their amides

additional charges, important roles in body

Characteristics of Basic AA

Amide group, basic + dipolar

Characteristics of aromatic AA

Added rings

Characteristics of Imino AA

Amine group in ring

What’s special about taurine?

NOT an AA, lack chiral C; needed for bile salts, antioxidants, cell membranes, electrolyte balance; ESSENTIAL IN CATS

AA functions

Protein synthesis (Muscle, tissue, hormones, enzyme formation), energy source, secondary functions

How are AA used as energy sources

remove amino group (excreted in urea cycle), oxidize carbon skeleton

Secondary function of histidine

Histamine (immune response)

Secondary function of cysteine

Glutathione (tripeptide/protein formation, antioxidant)

Secondary function of tyrosine

catecholamines (epinephrine), thyroid hormones

Secondary function of tryptophan

Serotonin, melatonin