Lipids lecture 3

Question 1

Fatty acid Synthesis

Answer 1

• Fatty acid synthase
• Occurs mainly in liver and adipocytes
• occurs in cytosol (cytoplasm)
• uses glucose to synthesis fatty acids
• NADH required

Question 2

3 stages of synthesis of fatty acids

Answer 2

1) Transport
2) loading
3)Condensation/reduction/dehydration/reduction

Question 3

How is manoyl Co A produced

Answer 3

carboxylation of acetyl CoA

Question 4

Transport

Answer 4

Acetyl CoA and amino acids exported from mitochondria

Question 5

citrate transport system

Answer 5

acetyl CoA from mitochondria - cytoplasm
1) the Acetyl CoA joins with oxaloacetate to form citrate
2) citrate is transported out the mitochondria via the citrate transporter in exchange for another molecule
3) in the cytoplasm ATP-citrate lyase converts citrate back into oxaloacetate and Acetyl CoA using ATP
4) oxaloacetate converted to maltate which is converted into pyruvate using a malic enzyme and generates NADHP

Question 6

Loading

Answer 6

1) carboxylation of acetyl CoA by acetyl CoA carboxylase
2) Synthesis of malonyl -ACP from malonyl CoA
ACP = Acyl carrier protein

Question 7

1. Condensation
2. Reduction

Answer 7

1. synthesis of acetoacetyl - ACP from malonyl-ACP and acetyl CoA
2. 3.
   4.

Question 8

Synthesis of triglycerols and phospholipids

Answer 8

1. formation of phosphatidate
   glycerols phosphate - lysophosphatidate - phosphatidate
   2.

Question 9

Differences between fatty acid synthesis and beta oxidation

Answer 9

cytoplasm vs mitochondria
3 C donor
fatty acyl carrier protein vs CoA derivatives
multi enzyme complex vs individual enzymes
oxidation - reduction co factors

Question 10

Regulation of FA metabolism

Answer 10

FA synthesis and beta oxidation are reciprocally regulated
Fed state: synthesis / storage is favoured
Fasting state : FA oxidation is favoured

Question 11

Control points for FA metabolism

Answer 11

Fed state : insulin levels increased
inhibits hydrolysis of stored triglycerols
stimulates formation of malonyl CoA which inhibits carinitine acyl transferase
Fasted state: Epinepherine/glucagon increase -
Epinepherin activates lipase to increase FA release
Glucagon inactivates malonyl CoA synthesis enzyme

Question 11

Isoprenoid synthesis (eg cholesterol)

Answer 11

synthesised in liver
liver derived/ dietary cholesterol both delivered to cells by lipoproteins
biosynthesis regulated by hormones and blood cholesterol levels