BIOCHEM 4 - AMINO ACIDS Flashcards Preview

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Flashcards in BIOCHEM 4 - AMINO ACIDS Deck (70):
1

Essential Amino acids

L, I, V, H, K, M, F, T, W

2

Non-essential amino acids

A, R, N, D, C, E, Q, G, P, S, Y

3

aa (obtained from nutrition)

Essential Amino acids

4

aa (synthesized by the body)

Non-essential amino acids

5

properties of AA (4)

Amphoteric
dipolar
optically active
tetrahedral structure

6

– reference to determine if the
amino acid has L- or D-configuration

α-amino group

7

All amino acids in naturally occurring proteins are

L-isomers

8


◦ derived from glutamate; neurotransmitters (has something to do with the brain)

GABA

9

GABA is derived from

glutamate

10


◦ derived from tryptophan; important in sleep

Serotonine

11

serotonine derived from

derived from tryptophan

12

3. Thyroxine

derived from tyrosine

13

indole acetic acid


4. Dopamine –

14

– side chain is a primary alcohol; looks like Ala with -OH



Serine

15

side chain is a secondary alcohol;

◦ Threonine

16

has two chirality centers

threonine and isoleucine

17

contains a thiol group; important in disulfide linkages; weak acid; can form H-bonds

◦ Cysteine

18

- ionized cysteine is -----, while the protonated form is much --------than serine.

polar
less polar

19

also has the ability to form covalent bonds called disulfide bonds between cysteine side chains.

Cysteine

20

– side chain is phenolic –OH; borderline case

Tyrosine

21

not very soluble in water, but contains a polar hydroxyl group in the para position of the phenyl ring

Tyrosine

22

amide groups do not become charged at biologically relevant pH values (i.e. pH 2-12), true or false

TRUE

23

simplest amino acid

GLYCINE

24

does not really have a polar or non-polar character

GLYCINE

25

- has much less steric hindrance than the other AAs;

GLYCINE

26

No chiral center/achiral

GLYCINE

27

no asymmetric carbon

GLYCINE

28

– side chain is isopropyl

Valine

29

side chain is isobutyl

Leucine

30

side chain is sec-butyl; has 2 chiral carbons

Isoleucine –

31

more hydrophobic than cysteine (S-containing amino acids)

Methionine

32

start amino acid

Methionine

33

having thioether

Methionine

34

– cyclic but not aromatic; 2ndary α-amino group or α-imino acid
- has a conformationally restricted structure

Proline

35

behaves more like a polar amino acid since ----- has a fairly high tendency to appear on the solvent-exposed surface of proteins

proline

36

– has an indole ring; borderline hydrophobic/polar

Tryptophan

37

what AA has the proton attached to the indole nitrogen can act as a hydrogen bond donor to water or other hydrogen bond acceptors

Tryptophan

38

majority of the large tryptophan side-chain is polar or not?.

non-polar

39

acidic form of asparagines; β-carboxyl group

Aspartate-

40

acidic form of glutamine; γ-carboxyl group

Glutamate–

41

– has a primary amino group
protonated at pH 7.0

◦ Lysine

42

contains ε-amino group

◦ Lysine

43

diamino acid

◦ Lysine

44

– most basic amino acid

Arginine

45

contains guanido group

Arginine

46

guanidinium ion always protonated

Arginine

47

heterocyclic ring side chain; not aromatic

Histidine

48

contains imidazole

Histidine

49

only amino acid that functions as buffer in physiological range

Histidine

50

all are very hydrophobic
absorbs UV at 280 nm
aromatic amino acids

Tyrosine, Tyr (Y)
Tryptophan, Trp (W)
Phenylalanine, Phe (F)

51

contain carboxyl groups (weaker than α-carboxyl group)
negatively charged at physiological pH;

Aspartate, Asp (D)
Glutamate, Glu (E)

52

present as conjugate bases
carboxyl groups function as nucleophiles in some enzymatic reactions

Aspartate, Asp (D)
Glutamate, Glu (E)

53

classified as β-branched
have greater steric hindrance
exhibit more restricted conformational flexibility

Valine, Val (V)
Isoleucine, Ile (I)
Threonine, Thr (T)

54

18 of the 19 L-amino acids have --- configuration

S

55

cysteine has -- configuration

R

56

is neither very
hydrophobic nor very hydrophilic.

Proline

57

As the pH increases, the charge on the molecule becomes

more negative,

58

as the pH decreases,
the charge on the molecule becomes

more positive.

59

zero net charge state is known as the

zwitterionic state

60

is capable of both accepting
and donating protons

zwitterion

61

characteristic of free amino acids with non-ionizable side chains near pH
7.0

zwitterion

62

At pH >> pKa, the ionizable group will be .
-

deprotonated

63

At pH >> pKa, For carboxylic acids, the group will be ____ charged;

negatively

64

At pH >> pKa, amines will be ____

neutral

65

At pH

protonated.

66

At pH

neutral

67

At pH

positively charged

68

has a chemically basic side chain but acidic pKa

histidine

69

pKa values of amino groups of common AA

occur in a range from pH 9 to pH 11

70

pKa values of carboxyl groups of common AA

ph 2

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