Lecture 3 amino acids

what can amino acids function as?

Amino acids can also function as neurotransmitters
(glutamate, -aminobutyric acid (GABA), hormones
(thyroxine), as bacterial cell wall components (D-
alanine) and as intermediates in many metabolic
pathways

all 20 amino acids share a common strucuture, name them.

All standard 20 amino acids used in genetic coding share a core structure:

• A central carbon (called the α-carbon)

• Attached to:

  • Amino group (–NH₃⁺)

  • Carboxyl group (–COO⁻)

  • Hydrogen atom (H)

  • An R group (or side chain) that varies between amino acids

what is happening to the amino acid at At physiological pH (~7.0):

• The amino group is protonated (+)

• The carboxyl group is deprotonated (–)
  → making the amino acid a zwitterion (has both + and – charges)

what differentiates amino acids?

• The R group is what differentiates each amino acid.

• It determines:

  • Chemical properties (e.g., polar, non-polar, acidic, basic)

  • Behavior in proteins

  • Hydrophobic/hydrophilic interactions

what are examples of Non-polar (aliphatic, hydrophobic) (7)

1. Glycine

2. Alanine

3. Valine

4. Leucine

5. Isoleucine

6. Proline

7. Methionin

what are examples of aromatic amino acids?

8. Phenylalanine

9. Tyrosine

10. Tryptophan

what are examples of Polar, uncharged, hydrophilic amino acids?

11. Serine (Ser, S)

12. Threonine (Thr, T

13. Cysteine (Cys, C)

14. Asparagine (Asn, N)

15. Glutamine (Gln, Q

what are examples of negative (acidic) amino acids?

16. Aspartic Acid (protonated) Aspartate (deprotonated)
    (Asp, D)

17. Glutamic Acid (protonated) Glutamate (deprotonated)
    (Glu, E)

what are examples of amino acids that are positive at ph 7 (basic)

18. Lysine (Lys, K)

19. Arginine (Arg, R

20. Histidine (His, H)

what do acidic amino acids do?

Acidic amino acids lose a proton at pH 7 and
are anionic

what do basic amino acids do?

Basic amino acids bind a H+ at pH 7 and are cationic