Classification of Amino Acids Flashcards

1
Q

Structure of Amino Acids

A
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2
Q

Acidic AAs

A
  1. Aspartic Acid
  2. Glutamic Acid
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3
Q

Aspartic Acid

A

Asp, D

aspartate - the anionic/deprotonated form

(how this amino acid is observed at physiological pH)

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4
Q

Glutamic Acid

A

Glu, E

glutamate - the anionic/deprotonated form

(how this AA is observed at physiological pH)

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5
Q

Basic AAs

A
  1. Lysine
  2. Arginine
  3. Histidine
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6
Q

Lysine

A

Lys, K

pKa = 10

cationic/protonated at physiological pH

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7
Q

Arginine

A

Arg, R

pKa = 12 at physiological pH

cationic/protonated at physiological pH

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8
Q

Histidine

A

His, H

pKa = 6.5 at physiological pH

can either be protonated (acidic) or deprotonated (basic)

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9
Q

Hydrophobic (Nonpolar) AAs

A
  1. Glycine
  2. Alanine
  3. Valine
  4. Leucine
  5. Isoleucine
  6. Phenylalanine
  7. Tryptophan
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10
Q

Characteristics of Hydrophobic/Nonpolar AAs

A
  1. either have aliphatic or aromatic side chains
  2. hydrophobic residues tend to associate with each other rather than with water
  3. therefore are found on the interior of folded globular proteins, away from water
  4. the larger the hydrophobic group, the greater the hydrophobic force repelling it from water
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11
Q

Glycine

A

Gly, G

aliphatic side chain

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12
Q

Alanine

A

Ala, A

aliphatic side chain

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13
Q

Valine

A

Val, V

aliphatic side chain

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14
Q

Leucine

A

Leu, L

aliphatic side chain

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15
Q

Isoleucine

A

Ile, I

aliphatic side chain

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16
Q

Phenylalanine

A

Phe, F

aromatic side chain

17
Q

Tryptophan

A

Trp, W

aromatic side chain

18
Q

Polar AAs

A
  1. Serine
  2. Threonine
  3. Tyrosine
  4. Asparagine
  5. Glutamine
19
Q

Characteristics of Polar AAs

A
  1. R-group is polar enough to form H-bonds but does not act as an acid or base
  2. are hydrophilic, that is they interact with water whenever possible
20
Q

Serine

A

Ser, S

21
Q

Threonine

A

Thr, T

22
Q

Tyrosine

A

Tyr, Y

23
Q

Asparagine

A

Asn, N

the amide derivative of aspartic acid

24
Q

Glutamine

A

Gln, Q

the amide derivative of glutamic acid

25
Q

Sulfur-Containing AAs

A
  1. Cysteine
  2. Methionine
26
Q

Cysteine

A

Cys, C

fairly polar

contains a thiol - an alcohol with an S instead of O

disulfide bridges - a covalent bond b/w 2 cysteine R-groups

when disulfide bonded becomes “cystine” which is more oxidized than cysteine (loss of 2 H’s)

27
Q

Methionine

A

Met, M

fairly non-polar

contains a thioether - an ether with an S instead of O

28
Q

Proline

A

Pro, P

the amino group is covalently bound to its nonpolar side chain - eliminates the N-H bond which disrupts the backbone hydrogen bonding in the polypeptide chain

this creates a secondary alpha-amino group and a distinctive ring structure

its unique structure forces it to kink the polypeptide chain