Metabolism of Fats

Question 1

Name the three primary sources fats are derived from

Answer 1

Diet
De novo biosynthesis in the liver
Storage depots in the adipose

Question 2

What is the role of bile salts?

Answer 2

Have hydrophilic groups on one face
Emulsify fats in intestine
Aid digestion of fat
And fat soluble vitamins e.g. A,D,E+K

Question 3

What does the weight loss medication Orlistat do?

Answer 3

Inhibits lipases
Reduces fat absorption by 30%
Excreted by faecal route

Question 4

What are Orlistat’s side effects?

Answer 4

Abdominal pain, urgency to defecate, increase flats and steatorrhea.

Question 5

State some characteristics of lipoproteins

Answer 5

Contain fatty acids within
Have hydrophilic outer core
Important for transport in aqueous blood

Question 6

What is a chylomicron?

Answer 6

Produced by enterocytes of the gut
Phospholipid monolayer with apoproteins
Transported via lymphatics and into bloodstream

Question 7

What does lipase do?

Answer 7

Recognises apoprotein, become activated- conformational change
Digests triglycerides, fatty acids released and taken up by cell
Glycerol remains in bloodstream

Question 8

What are cholesterol esters?

Answer 8

Synthesised in plasma from cholesterol and a acyl chain
More hydrophobic
Packs better

Question 9

Lifecycle of VLDL, HDL, IDL +LDL

Answer 9

Produced in liver
VLDL delivers triacylglycerides + cholesterol to skeletal muscle, adipose and tissues
Lipid depleted remnant has new density, transfers apoproteins to HDL
Leaves IDL
Cholesterol esters packaged into IDL giving LDL
Remnants of LDL taken up by liver or taken up by macrophages

Question 10

What do HDL’s do?

Answer 10

‘Good cholesterol’

Takes cholesterol from peripheral tissues back to liver for disposal

Question 11

What do LDL’s do?

Answer 11

‘Bad cholesterol’
Prolonged elevated LDL can lead to atherosclerosis
They transport cholesterol from the liver to peripheral tissues

Question 12

What % of energy needs comes from fatty acid metabolism?

Answer 12

50%

Question 13

Where does Beta-oxidation take place? What does it do?

Answer 13

Mitochondrion: outer membrane

Produces Acetyl-CoA to be fed into TCA cycle

Question 14

How does Beta-oxidation occur?

Answer 14

Uses the hydrolysis of two phosphoanhydride bonds
Catalysed by Acetyl-CoA synthetase
Converts fatty acid to Acetyl-CoA

Question 15

What does the cartinine shuffle do?

Answer 15

Transports the Acetyl-CoA synthesised via Beta oxidation into the matrix

Question 16

How does the carnitine shuffle work?

Answer 16

Acetyl-CoA coupled to carnitine forming acyl carnitine

Cartnitine and acyl carnitine moved to and from the matrix by translocase

Question 17

What does the Beta oxidation cycle consist of?

Answer 17

Series of oxidation, hydration, oxidation and thiolysis reactions.

Question 18

What does the beta-oxidation cycle produce?

Answer 18

1 Acetyl-CoA
1 Acyl-CoA
1 FADH2
1NADH
For each turn

Question 19

What are the two enzymes involved in lipogenesis?

Answer 19

Acetyl CoA Carboxylase

Fatty acid Synthase

Question 20

How are fatty acids formed?

Answer 20

Decarboxylative condensation reactions involving acetyl-CoA and Malonyl CoA
Chain elongates 2C at a time
After each elongation undergoes reduction, dehydration and reduction
Uses acyl carrier proteins