Metabolic Biochemistry

Question 1

What is the role of cholesterol in the plasma membrane? (9)

Answer 1

• Component of membranes
• Regulates fluidity
  slide 4

Question 2

What is cholesterol? (9)

Answer 2

• Precursor of steroid hormone
  (such as progesterone, testosterone, oestradiol, hydrocortisone (cortisol) and vitamin D
  Slide 5

Question 3

Where is cholesterol found? (9)

Answer 3

Carried in plasma in lipoproteins
Slide 5

Question 4

Where does Cholesterol synthesis take place? (9)

Answer 4

In the liver and small intestine
Slide 8

Question 5

Slide 9 - Cholesterol synthesis -
Acetly CoA + acetoacetyl CoA
——>
(9)

Answer 5

3-hydroxy-3-methylglutaryl CoA

Question 6

Cholesterol synthesis :
3-hydroxy-3methylglutaryl CoA
——->
(9)

Answer 6

Mevalonate
(slide 9)

Question 7

Cholesterol synthesis : Mevalonate ——>
(9)

Answer 7

Squalene
(slide 9)

Question 8

Cholesterol synthesis: Squalene ——->
(9)

Answer 8

Cholesterol
slide 9

Question 9

Outline the entire cholesterol synthesis steps (9)

Answer 9

acetyl CoA + acetoacetyl CoA
——->
3-hydroxy-3-methylglutaryl CoA
—–>
mevalonate
——–>
squalene
———>
cholesterol
Slide 9

Question 10

Synthesis of 3-hydroxy-3-methylglutaryl CoA (9) (HMG CoA)

Answer 10

Acetyl CoA + Acetoacetyl CoA ——–> 3-hydroxy-3-methylglutaryl CoA
Slide 10

Question 11

What is the rate controlling step between HMG CoA to mevalonate? (9)

Answer 11

3-Hydroxy-3-methylglutaryl CoA reductase
slide 11

Question 12

Control of HMG CoA reductase: Describe how mRNA synthesis is inhibited. (9)

Answer 12

Cholesterol inhibits the translation of mRNA and stimulate enzyme degradation as a long term control

Phosphorylation to AMP - activated protein kinase inhibits acutely

**Inhibited by drugs (statins)
slide 12

Question 13

How are Cholesterol transported?
(9)

Answer 13

Cholesterol and triacylglycerol is readily soluble in plasma
Transported in lipoproteins
Slide 13

Question 14

Major lipoproteins: Dietary triacylglycerol? (9)

Answer 14

Chylomicrons
Slide 15

Question 15

Major lipoproteins: Endogenous triacylglycerol? (9)

Answer 15

Very low density lipoprotein (VLDL)
slide 15

Question 16

Major lipoproteins: Cholesteryl ester? (9)

Answer 16

Intermediate density lipoprotein
(IDL)
Slide 15

Question 17

Major Lipoprotein: Cholesteryl ester? (9)

Answer 17

Low density lipoprotein (LDL)
Slide 15

Question 18

Major Lipoprotein: Phospholipid/cholesteryl ester? (9)

Answer 18

High density lipoprotein (HDL)
Slide 15

Question 19

HDL versus Chylomicrons - Protein is denser than lipid (9)

Answer 19

e.g. chylomicrons are 2% protein/98% lipid by weight
and have density of <0.95 g/ml
HDL is 55% protein/45% lipid
and has density 1.063-1.21 g/ml
Chylomirons have a mean
diameter of 400 nm
HDL is about 10 nm
Slide 16

Question 20

What is Lipoprotein Lipase? (9)

Answer 20

Enzyme bound to lumenal surface of endothelial cells in capillaries mainly in skeletal muscle, adipose tissue and heart
Slide 21