Ch. 3: Amino Acids

Question 1

What are the nonpolar hydrophobic amino acids?

Answer 1

valine, alanine, glycine, leucine, isoleucine, proline, methionine, phenylalanine, tryptophan

Question 2

What are the polar, positively charged, basic amino acids?

Answer 2

histidine, lysine, arginine

Question 3

What are the polar, negatively charged, acidic amino acids?

Answer 3

aspartate, glutamate

Question 4

What are the polar, neutral amino acids?

Answer 4

cysteine, asparagine, glutamine, serine, threonine, tyrosine

Question 5

What are the essential amino acids?

Answer 5

methionine, isoleucine, leucine, lysine, valine, phenylalanine, threonine, tryptophan

Question 6

What are the conditionally essential amino acids?

Answer 6

glutamine, histidine, arginine

Question 7

What are the non-essential amino acids?

Answer 7

glycine, proline, serine, tyrosine, aspartate, alanine, asparagine, cysteine, glutamate

Question 8

Glycine: 4 important functions?

Answer 8

1) collagen: every third position a.a.
2) biosynthesis: porphryns & purines
3) bile acids conjugation
4) neurotransmitter: + or -

Question 9

Disease associated with glycine?

Answer 9

non-ketotic hyperglycinemia (NKH): Inborn error of glycine degradation, effects CNS ➡️ death

Question 10

Alanine: important function?

Answer 10

Link between a.a. & CHO metabolism

Question 11

Valine, leucine, isoleucine: important function?

Answer 11

Stabilize 3D structure (hydrophobic) of polymer

Question 12

Disease associated with valine, leucine, & isoleucine?

Answer 12

Maple syrup urine disease

Question 13

Disease associated with phenylalanine?

Answer 13

Phenylketonuria: low levels of phenylalanine hydroxylase ➡️ build up of Phe

Question 14

What are the 4 hydroxylation reactions that need BH4 as cofactor?

Answer 14

1) Phe ➡️ Tyr
2) Tyr ➡️ L-dopa
3) Trp ➡️ S-hydroxytrp
4) Arg ➡️ NO + citrulline

Question 15

Tryptophan: important function?

Answer 15

Precursor for serotonin, melatonin, nicotinamide

Question 16

Methionine: important function?

Answer 16

Methyl group donor (SAM)

Question 17

Proline: 2 important functions?

Answer 17

1) intro restrictions on folding of polypeptide chain

2) collagen synthesis

Question 18

What are the 2 important hydroxylases for collagen synthesis? What vitamin is needed for hydroxylase rxn?

Answer 18

Proline & lysine hydroxylase

Vitamin C

Question 19

Aspartate: important function?

Answer 19

On surface of water-soluble proteins

Question 20

Glutamate: important function?

Answer 20

+ neurotransmitter in brain

Question 21

Disease associated with glutamate? Drugs that help treat?

Answer 21

Amyotrophic lateral sclerosis (ALS): glu excitotoxicity

Riluzole & gabapentin (GABA analog)

Question 22

Gamma-carboxyglutamate: important function? What vitamin is needed for formation?

Answer 22

Blood coagulation & anti-coagulation proteins

Vitamin K

Question 23

Lysine: 4 important functions?

Answer 23

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

Question 24

Histidine: 2 important functions?

Answer 24

1) essential for infants & uremia pts

2) precursor for histamine (His - carboxyl group)

Question 25

What are the 2 histamine receptors? Where are they found? Antagonizing of these receptors treats what diseases?

Answer 25

H1: smooth muscle contraction; Tx allergic disorders

H2: secrete HCl in stomach, ⬆️ ❤️ rate; Tx gastric ulcers

Question 26

What toxins bind to dipthamide (inhibits translation)?

Answer 26

1) Diphtheria
2) Cholera
3) Pertussis

Question 27

Arginine: 2 important functions?

Answer 27

1) creatine synthesis, urea cycle

2) NO synthesis

Question 28

Serine & threonine: 2 important functions?

Answer 28

1) form esters with phosphoric acid
2) form glycosides with sugars (O-linked)

Used in regulatory reactions for proteins

Question 29

Cysteine: important function?

Answer 29

Forms disulfide bridges (SS bonds) ➡️ cystine

Used in protein folding

Question 30

Selenocysteine: important function?

Answer 30

In active sites of redox reaction enzymes

Question 31

Disease associated with selenocysteine?

Answer 31

Keshan disease (essential trace element)

Question 32

Tyrosine: 3 important functions?

Answer 32

1) sulfated in gastrin & CCK
2) phosphorylated in insulin, EGF, PDGF, ILG
3) Precursor for thyroxine, catecholamines, melanin, Phe

Question 33

Disease associated with tyrosine?

Answer 33

Tyrosinemia (tyrosinosis): can’t break down tyrosine

Question 34

Glutamine: 3 important functions?

Answer 34

1) synthesis of purines & pyrimidines
2) acid/base regulation (urea ➡️ NH3 ➡️ NH4+ + H+)
3) boosts immunity of surgical pts

Question 35

Beta-alanine: function?

Answer 35

Part of pantothenic acid (vit B5)

Question 36

Taurine: 2 functions?

Answer 36

1) present in CNS

2) conjugate bile acids

Question 37

GABA (gamma-aminobutyric acid): function?

Answer 37

• neurotransmitter, important in ALS

Question 38

Hypoglycin A: importance?

Answer 38

Causes severe hypoglycemia when ingested

Question 39

What is D-penicillamine used to treat?

Answer 39

Chelates metals; Tx Wilson’s disease (copper accumulation in pupils)

Question 40

What diseases is N-acetylcysteine used to treat?

Answer 40

1) Acetaminophen toxicity
2) replenish glutathione stores in liver
3) Cystic fibrosis
4) prevents further renal impairment

Question 41

What disease is gabapentin used to treat?

Answer 41

ALS; anticonvulsant

Question 42

What is pI (isoelectric point)? Equation?

Answer 42

pH at which molecule has 0 net charge

pI = (pK1 + pK2 / 2)

Question 43

What amino acids have buffering capacity in physiological pH?

Answer 43

Cysteine & histidine

Question 44

What amino acids does trypsin cleave at?

Answer 44

Lys & Arg at carboxy end

Question 45

What amino acids does chymotrypsin cleave at?

Answer 45

Phe, Trp, & Tyr at carboxy end

Question 46

What amino acids does cyanogen bromide cleave at?

Answer 46

Met at carboxy end