Cell metabolism 2 - Lipids

Question 1

What is the main product of fatty acid metabolism?

Answer 1

Acetyl CoA

Question 2

What 3 primary sources are fats derived from?

Answer 2

1. The diet
2. De nonvo synthesis(liver:
3. Storage depots in adipose tissue

Question 3

Where are bile salts made and stored?

Answer 3

Made - Liver

Stored - Gall bladder

Question 4

What do bile salts do during digestion?

Answer 4

They pass from the bile duct to the intestine.

They emulsify fats aiding their digestion and absorption of fats and also that of fat-soluble viamins, e.g. A, D, E, K

Question 5

What is orlistat?

Answer 5

A medicine which reduced fat absorption by 30%, which is then secreted by the faecal route. It is a inhibitor of gastric and pancreatic lipases.
This can help treat patients with obesity.
Side effects are abdominal pain, urgency to defecate, increased flatus and steatorrhea.

Question 6

What are lipoproteins?

Answer 6

Molecules in the blood that transport lipids

Question 7

What is a lipoprotein?

Answer 7

A molecule that has a cholesterol monolayer and apoproteins, which surround a core of cholesterol esters and triacylglycerols

Question 8

Where do chylomicrons get apoproteins from?

Answer 8

From HDLs in the bloodstream

Question 9

Where are chylomicrons obtained from and how do they enter the body?

Answer 9

From digested food that are absorbed by entrocytes are on the border of the small intestine

Question 10

How do chylomicrons travel through the body?

Answer 10

Through the lymphatic system

Question 11

Where are lipoprotein lipases found?

Answer 11

On the capillary endothelial cells lining adipose, heart and skeletal muscle tissues

Question 12

What is the life cycle of a chylomicron?

Answer 12

1. Nascent chylomicron absorbed by intestinal villi
2. Nascent chylomicron gains apoproteins from HDLs
3. Chylomicrons with apoproteins can recognise and activate lipoproteins on the surface of endothelial cells lining adipose and muscle tissue. This results in the hydrolysis of triglycerides into free fatty acids(FFA) and glycerol. FFA can be taken up by tissues and glycerol is taken up by the liver for gluceoneogenesis.
4. The empty/near empty chylomicrons then gain more apoproteins from HDLs and they are used up in the liver to produce VLDL

Question 13

Draw the life cycle of VLDLs, IDLs, HDLs and LDLs

Answer 13

Look on one note

Question 14

Why are HDLs referred to as ‘good cholesterol’ and LDLs as ‘bad cholesterol’?

Answer 14

HDLs:
Take cholesterol from peripheral tissues back to the liver for use or disposal. Help lower total serum cholesterol. Reverse cholesterol transport.
LDLs:
Prololonged elevation of LDLs leads to atherosclerosis. More than 40% of their weight are cholesterol esters.

Question 15

What is Beta -oxidation of fatty acids?

Answer 15

When fatty acids are converted into an acyl CoA species

Question 16

What is the carnitine shuttle?

Answer 16

The acyl CoA species formed in Beta-oxidation has to enter the matrix of the mitochondria so it couples with carnitine to form acyl carnitine. Carnitine and acyl carnitine and moved to a from the matrix by a transolcase in the mitochondrial membrane

Question 17

What is primary-carnitine deficiency?

Answer 17

It is a autosomal recessive disorder which causes a mutation to a carnitine transporter resulting in reduced ability for cells to uptake carnitine, needed for Beta-oxidation.
Symptoms can be encephalopathies, cardiomyopathies, muscle weakness and hypoglycaemia.

Question 18

When are ketone bodies formed?

Answer 18

When the Beta-oxidation > carbohydrate metabolism..

Question 19

What enzymes are involved in lipogenesis?

Answer 19

Acetyl CoA carboxylase and Fatty acid synthase

Question 20

How are fatty acids synthesised?

Answer 20

By decarboxylative condensation reactions involving acetyl-CoA and malonyl-CoA

Question 21

What are the distinctions between fatty acid synthesis and degradation?
Carriers?
Reducing power?
Location?

Answer 21

Carriers:
ACP(S) vs CoA(D)
Reducing power:
NADPH(S) vs FAD/NAD+(D)
Locations:
Cytoplasm(S) vs Mitochondrial matrix(D)