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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