6- Lipid Metabolism

Question 1

Define amphipathic

Answer 1

Both hydrophilic and phobic components

Question 2

What can lack of bile salts result in

Answer 2

Steatorrhea. Orlistat can be used to treat obesity in this way by inhibiting lipases

Question 3

Where does beta oxidation occur

Answer 3

Mitochondria

Question 4

What is the 1st beta oxidation step

Answer 4

Fatty acid+ HS-CoA + ATP -> AMP+ acyl CoA + PPi

Question 5

Describe the carnitine shuttle

Answer 5

acyl coA is coupled to the carnitine and forms an acyl carnitine using the enzyme carnitine parmitoyltransferase I and the coA remains in the cytosol
it diffuses across the outer mitochondrial membrane into the intramembranous space, via translocation antiporter
. When it transports the acyl carnitine species in, it transports a molecule of carnitine out of the matrix
When in the mitochondrial matrix, a membrane bound carnitine parmitoyltransferase II catalyses the reaction to regenerate the acyl coA species and the carnitine is uncoupled from the acyl species

Question 6

What are the enzymes in the carnatine shuttle

Answer 6

Carnitine parmitoyltransferase 1 and 2

Question 7

What is the enzyme in the first beta oxidation step

Answer 7

Aycl coa synthetase

Question 8

In one cycle of β oxidation, how many carbons are lost from the acyl coA species

Answer 8

2

Question 9

What is produced from a beta oxidation cycle

Answer 9

FADH2, 1 NADH and 1 acetyl coA

Question 10

Describe the beta oxidation cycle:

Answer 10

Oxidation: of aycl coa by FAD by enzyme acyl coA dehydrogenase
Hydration : by 3 hydroxyacyl coA hydrolase
Oxidation: by NAD+ by 3- hydroxyacyl coA dehydrogenase
Thiolysis: by β ketothiolase to give a acyl coA species shortened by 2 carbons and an acetyl coA species

Question 11

How many atp molecules are produced from palminate

Answer 11

7NADH=7×3ATP=21ATP
7FADH2 =7×2ATP=14ATP
8acetyl coA=8×12ATP=96ATP
  In total = 131 ATP
-2 from 1st step = 129atp

Question 12

Describe the first lipogenesis step

Answer 12

Acetyl coA to (requires atp) malonyl coA to malonyl ACP (requires acp)
Also acetyl coA to acetyl ACP (requires ACP)

Question 13

What is the second step of lipogenesis

Answer 13

o Condensation
o Reduction
o Dehydration
o Reduction

Question 14

What is the overall reaction for forming palmitate

Answer 14

acetyl coA + 7 malonyl coA + 14 NADPH + 14 H

To palmitate + 7 CO2 + 6H2O + 8 HS coA + 14 NADP+

Question 15

What is MCADD

Answer 15

Medium chain acyl coenzyme A dehydrogenase deficiency
Acyl coA dehydrogenase catalyses the reaction that converts the acyl coA species into a trans Δ2 enoyl coA species in the β oxidation of fatty acids

patients should never be allowed to fast, fatty acid metabolism should not be counted on

Question 16

What is primary carnitine deficiency

Answer 16

mutations in a gene known as SLC22A5, which encodes the carnitine transporter, resulting in a reduced ability of cells to take up carnitine, which is needed to transport acyl coA species into the mitochondria for β oxidation
Symptoms: encephalopathies,
cardiomyopathies, muscle weakness and hypoglycaemia

Question 17

What are the2 enzymes of fatty acid synthesis

Answer 17

Fatty acid biosynthesis does involve just two enzymes, Acetyl CoA Carboxylase and Fatty acid synthase (FAS). This latter molecule is a large polypeptide with seven different enzymatic activities.