Ch. 3: Amino Acids Flashcards
What are the nonpolar hydrophobic amino acids?
valine, alanine, glycine, leucine, isoleucine, proline, methionine, phenylalanine, tryptophan
What are the polar, positively charged, basic amino acids?
histidine, lysine, arginine
What are the polar, negatively charged, acidic amino acids?
aspartate, glutamate
What are the polar, neutral amino acids?
cysteine, asparagine, glutamine, serine, threonine, tyrosine
What are the essential amino acids?
methionine, isoleucine, leucine, lysine, valine, phenylalanine, threonine, tryptophan
What are the conditionally essential amino acids?
glutamine, histidine, arginine
What are the non-essential amino acids?
glycine, proline, serine, tyrosine, aspartate, alanine, asparagine, cysteine, glutamate
Glycine: 4 important functions?
1) collagen: every third position a.a.
2) biosynthesis: porphryns & purines
3) bile acids conjugation
4) neurotransmitter: + or -
Disease associated with glycine?
non-ketotic hyperglycinemia (NKH): Inborn error of glycine degradation, effects CNS ➡️ death
Alanine: important function?
Link between a.a. & CHO metabolism
Valine, leucine, isoleucine: important function?
Stabilize 3D structure (hydrophobic) of polymer
Disease associated with valine, leucine, & isoleucine?
Maple syrup urine disease
Disease associated with phenylalanine?
Phenylketonuria: low levels of phenylalanine hydroxylase ➡️ build up of Phe
What are the 4 hydroxylation reactions that need BH4 as cofactor?
1) Phe ➡️ Tyr
2) Tyr ➡️ L-dopa
3) Trp ➡️ S-hydroxytrp
4) Arg ➡️ NO + citrulline
Tryptophan: important function?
Precursor for serotonin, melatonin, nicotinamide
Methionine: important function?
Methyl group donor (SAM)
Proline: 2 important functions?
1) intro restrictions on folding of polypeptide chain
2) collagen synthesis
What are the 2 important hydroxylases for collagen synthesis? What vitamin is needed for hydroxylase rxn?
Proline & lysine hydroxylase
Vitamin C
Aspartate: important function?
On surface of water-soluble proteins
Glutamate: important function?
+ neurotransmitter in brain
Disease associated with glutamate? Drugs that help treat?
Amyotrophic lateral sclerosis (ALS): glu excitotoxicity
Riluzole & gabapentin (GABA analog)
Gamma-carboxyglutamate: important function? What vitamin is needed for formation?
Blood coagulation & anti-coagulation proteins
Vitamin K
Lysine: 4 important functions?
1) linked to biotin, lipoic acid, retinal
2) collagen synthesis
3) cross links for tensile strength & insolubility in elastin & collagen
4) blood clotting: cross-linking in fibrin
Histidine: 2 important functions?
1) essential for infants & uremia pts
2) precursor for histamine (His - carboxyl group)
What are the 2 histamine receptors? Where are they found? Antagonizing of these receptors treats what diseases?
H1: smooth muscle contraction; Tx allergic disorders
H2: secrete HCl in stomach, ⬆️ ❤️ rate; Tx gastric ulcers
What toxins bind to dipthamide (inhibits translation)?
1) Diphtheria
2) Cholera
3) Pertussis
Arginine: 2 important functions?
1) creatine synthesis, urea cycle
2) NO synthesis
Serine & threonine: 2 important functions?
1) form esters with phosphoric acid
2) form glycosides with sugars (O-linked)
Used in regulatory reactions for proteins
Cysteine: important function?
Forms disulfide bridges (SS bonds) ➡️ cystine
Used in protein folding
Selenocysteine: important function?
In active sites of redox reaction enzymes
Disease associated with selenocysteine?
Keshan disease (essential trace element)
Tyrosine: 3 important functions?
1) sulfated in gastrin & CCK
2) phosphorylated in insulin, EGF, PDGF, ILG
3) Precursor for thyroxine, catecholamines, melanin, Phe
Disease associated with tyrosine?
Tyrosinemia (tyrosinosis): can’t break down tyrosine
Glutamine: 3 important functions?
1) synthesis of purines & pyrimidines
2) acid/base regulation (urea ➡️ NH3 ➡️ NH4+ + H+)
3) boosts immunity of surgical pts
Beta-alanine: function?
Part of pantothenic acid (vit B5)
Taurine: 2 functions?
1) present in CNS
2) conjugate bile acids
GABA (gamma-aminobutyric acid): function?
- neurotransmitter, important in ALS
Hypoglycin A: importance?
Causes severe hypoglycemia when ingested
What is D-penicillamine used to treat?
Chelates metals; Tx Wilson’s disease (copper accumulation in pupils)
What diseases is N-acetylcysteine used to treat?
1) Acetaminophen toxicity
2) replenish glutathione stores in liver
3) Cystic fibrosis
4) prevents further renal impairment
What disease is gabapentin used to treat?
ALS; anticonvulsant
What is pI (isoelectric point)? Equation?
pH at which molecule has 0 net charge
pI = (pK1 + pK2 / 2)
What amino acids have buffering capacity in physiological pH?
Cysteine & histidine
What amino acids does trypsin cleave at?
Lys & Arg at carboxy end
What amino acids does chymotrypsin cleave at?
Phe, Trp, & Tyr at carboxy end
What amino acids does cyanogen bromide cleave at?
Met at carboxy end
