Amino Acids

Question 1

What are the five general functions of amino acids? Give an example of each.

Answer 1

1. Catalysts (e.g. enzymes).
2. Transport (e.g. haemoglobin).
3. Structure (e.g. keratin).
4. Motion (e.g. myosin/actin).
5. Signalling (e.g. insulin receptor).

Question 2

What structure do catalysts have? And what type of amino acids make-up catalysts?

Answer 2

• Linear-heteropolymers of alpha-amino acids.
• Non-polar, aliphatic R groups.

Question 3

What can transport molecules (e.g. Haemoglobin) do? And what type of amino acids make-up transportation molecules.

Answer 3

• Can: polymerize (form chains).
• Aromatic R groups.

Question 4

What properties do structural molecules (e.g. keratin) have? And what type of amino acids make-up structural molecules.

Answer 4

• Has: acid-base properties.
• Polar, uncharged R groups.

Question 5

What properties do motion ‘molecules’ (e.g. myosin/actin) have? And what type of amino acids make-up motion ‘molecules’.

Answer 5

• Has: Varied physical props, allowing proteins to have different properties.
• Positively charged R groups.

Question 6

What properties do signaling molecules (e.g. insulin receptors) have? What types of amino acids make-up signalling molecules?

Answer 6

• Has: varied chemical functionality.
• Negatively charged R groups.

Question 7

True or false: all amino acids (except one) are chiral. If TRUE which amino acid is NOT chiral?

Answer 7

True.
Gly is the only amino acid that is not chiral.

Question 8

Do proteins contain L-amino acids, D-amino acids, or both?

Answer 8

Only L-amino acids.

Question 9

What are the two types of ionisable groups in proteins?

Answer 9

Acids and bases.

Question 10

What is the equation for acids?

Answer 10

HA –> A- + H+

Question 11

What is the equation for bases?

Answer 11

HB- –> B + H+

Question 12

What does it mean when pKa = pH when [HB-] = [B]

Answer 12

50% ionisation. pKa = pH at which ionizable group is 50-50 population split w/ protonated and deprotonated form.

Question 13

What amino acids are acidic? And what are their pH values?

Answer 13

C-ter (3.1). Asp/Glu (4.4).

Question 14

What amino acids are neutral? What is their pH value?

Answer 14

His (6.5).

Question 15

What amino acids are basic? What are their pH values?

Answer 15

N-ter (8.0). Cys (8.5). Tyr (10.0). Lys (10.0). Aug (12.0).

Question 16

How many different types of side chains are there? List them.

Answer 16

There are seven side chains.
1. Acidic side chains.
2. Basic side chains.
3. Uncharged polar amino acids (amides).
4. Uncharged polar amino acids (hydroxyls).
5. Aromatic Amino acids.
6. Non-polar amino acids.
7. Sulphur-containing amino acids.

Question 17

What are the two types of Acidic side chains?

Answer 17

Asp (D) and Glu (E).

Question 18

What are the general notes on acidic side chains?

Answer 18

1. Completely ionised, negatively charged at physiological pH (7.4).
2. Very polar.
3. Act as chelating agents (claw) for metal ions.

Question 19

What are the properties of the two Acid side chain examples?

Answer 19

1. Asp (D) = Trignonal planar.
2. Gly (E) = Extra methyl (compared to Asp)