Categorising Amino Acids

Question 1

Lys, K

Lysine

Answer 1

Positively charged at physiological pH.

Question 2

Cys, C

Cysteine

Answer 2

Contains -SH group, much more reactive, can form disulphide bonds.

Question 3

Glu, E

Glutamate

Answer 3

Negatively charged at physiological pH.

Question 4

Arg, R

Arginine

Answer 4

Positively charged at physiological pH.

Question 5

Leu, L

Leucine

Answer 5

Aliphatic R-Group (Hydrophobic)

Question 6

Gly, G

Glycine

Answer 6

Aliphatic R-Group (Hydrophobic)
Only amino acid that doesn’t display chirality.

Single H atom as its R-group.

Question 7

Thr, T

Threonine

Answer 7

Polar R-Group (Hydrophilic)

Contains additional chiral centre - only 1 isomer found in proteins.

Question 8

Asn, N

Asparagine

Answer 8

Polar R-Group (Hydrophilic)

Question 9

Gln, Q

Glutamine

Answer 9

Polar R-Group (Hydrophilic)

Question 10

Phe, F

Phenylalanine

Answer 10

Aromatic R-Group

Question 11

Val, V

Valine

Answer 11

Aliphatic R-Group (Hydrophobic)

Question 12

Proline

Answer 12

Hydrophobic R-group. Cyclic structure makes it more conformationally restricted than other amino acids.

Question 13

Tyrosine

Answer 13

Aromatic R-Group

Question 14

Trp, W

Tryptophan

Answer 14

Aromatic R-Group

Question 15

His, H

Histidine

Answer 15

Positively charged at physiological pH.

Question 16

Ile, I

Isoleucine

Answer 16

Aliphatic R-Group (Hydrophobic)

Contains additional chiral centre - only 1 isomer found in proteins.

Question 17

Ser, S

Serine

Answer 17

Polar R-Group (Hydrophilic)

Question 18

Ala, A

Alanine

Answer 18

Aliphatic R-Group (Hydrophobic)

Methyl group side chain.

Question 19

Asp, D

Aspartate

Answer 19

Negatively charged at physiological pH.

Question 20

Met, M

Methionine

Answer 20

Aliphatic R-Group (Hydrophobic)

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