Week 7 (fatty acid synthesis and beta oxidation)

Question 1

Why is fatty acid synthesis required?

Answer 1

Energy storage
Extracellular and intracellular messengers
Hormones
Co-factors
Transporters
Pigments
Detergents
Cell membrane components

Question 2

What does the fatty acid synthesis process involve?

Answer 2

Repeated cycles of reactions, with each cycle adding two carbon units for malonyl-CoA to a growing fatty acid chain.

Question 3

Name the 4 steps of fatty acid synthesis

Answer 3

1. condensation
2. reduction I
3. dehydration
4. reduction II

Question 4

Explain what happens during condensation in fatty acid synthesis

Answer 4

acetyl-CoA and malonyl-CoA are condensed by fatty acid synthase, releasing one molecule of carbon dioxide.

Question 5

Explain what happens during reduction I in fatty acid synthesis

Answer 5

The beta-keto group formed after condensation is reduced by NADPH to form a hydroxyl group.

Question 6

Explain what happens during dehydration in fatty acid synthesis

Answer 6

The hydroxyl group is dehydrated, resulting in the formation of a double bond between carbons 2 and 3.

Question 7

Explain what happens during reduction II in fatty acid synthesis

Answer 7

The double bond is reduced by NADPH, yielding a saturated fatty acid chain elongated by two carbons.

Question 8

Where does fatty acid synthesis take place?

Answer 8

Cytoplasm

Question 9

How is fatty acid synthesis regulated?

Answer 9

Transcriptional regulation
Allosteric regulation
Hormonal regulation
Post-translational regulation
Nutrient availability

Question 10

What enzymes catalyses fatty acid synthesis?

Answer 10

Fatty acid synthase (FAS)

Question 11

What is another phrase for fatty acid catabolism?

Answer 11

Beta-oxidation

Question 12

Why is fatty acid catabolism required?

Answer 12

Provide energy
Maintain metabolic homeostasis
Mobilise stored energy reserves
Regulate lipid metabolism
Produce ketone bodies

Question 13

Where does fatty acid catabolism take place?

Answer 13

Mitochondrial matrix

Question 14

How is fatty acid catabolism regulated?

Answer 14

Transcriptional regulation
Allosteric regulation
Hormonal regulation
Post-translational modifications
Substrate availability and energy status

Question 15

What needs to occur before beta-oxidation can begin?

Answer 15

Fatty acids must attach to CoA to become activated and are then transported across the mitochondrial membrane via a series of enzymatic reactions known as the carnitine shuttle.

Question 16

What does the beta-oxidation process involve?

Answer 16

A series of 4 enzymatic reactions that are repeated until the fatty acid is completely oxidised.

Question 17

Name the 4 stages of beta-oxidation

Answer 17

Oxidation I
Hydration
Oxidation II
Thiolysis

Question 18

Explain what happens during oxidation I in beta-oxidation

Answer 18

Oxidation of the fatty acid by a flavoprotein dehydrogenase enzyme, leading to the formation of a trans-double bond between the alpha and beta carbons of the fatty acyl-CoA molecules. The reaction also generates FADH2.

Question 19

Explain what happens during hydration in beta-oxidation

Answer 19

The trans-double bond is then hydrated by enoyl-CoA hydratase, resulting in the formation of a hydroxyl group at the beta carbon.

Question 20

Explain what happens during oxidation II in beta-oxidation

Answer 20

The hydroxyl group is oxidised to a carbonyl group by 3-hydroxaxyle-CoA dehydrogenase, producing NADH.

Question 21

Explain what happens during thiolysis in beta-oxidation

Answer 21

The beta-ketoacyl-CoA molecule is cleaved by thiolase, releasing a molecule of acetyl-CoA and leaving behind a fatty acyl-CoA molecule shortened by two carbons. The newly formed acetyl-CoA can enter the citric acid cycle for further oxidation.