Fatty Acids

Question 1

What is the reaction responsible for the formation of polyketide chains?

Answer 1

claisen condensation = poly beta ketone chains

- joins acetates together

Question 2

What is CoA made up of?

Answer 2

an adenine nucleotide
pantothenic acid - from vitamin B3
NHCH2CH2SH = thiol linker which is where the acetate binds

Question 3

Why is a thioester better at claisen condensation than an oxygen ester?

Answer 3

thioesters are more acidic than oxygen esters (are better enolates)
- there is less overlap between the p-orbitals with C and S than with C and O meaning there is less internal resonance
= internal resonance reduces acidity

RS is a better leaving group than RO
- is a more stable species

Question 4

How are acetate and malonate carried around the body?

Answer 4

acetate and malonate are carried by CoA

- are linked at the thiol

Question 5

What are the factors required to convert acetate to malonate?

Answer 5

carbon dioxide - in the form of HCO(2-)
ATP
biotin co-enzyme

reaction is catalysed by acetyl-CoA carboxylase

Question 6

How are acetate and malonate linked to enzyme fatty acid synthase during saturated fatty acids synthesis?

Answer 6

malonyl is linked to the acyl carrier protein

acetate is linked via a sulphur on a cystein residue of the enzyme

Question 7

How are saturated fatty acids synthesised?

Answer 7

are synthesised by enzyme fatty acid synthase

malonate and acetate are joined together to form saturated fatty acids

• malonyl is linked to the to the fatty acid synthase via acyl carrier protein
• acetate is linked to the fatty acid synthase via a sulphur of a cystein residue of the enzyme