Lipids & metabolism

Question 1

What is beta oxidation?

Answer 1

the degradation of fatty acid into acetyl CoA
note: only occurs in the mitochondria

Question 2

simple steps of beta oxidation?

Answer 2

starts with fatty acyl CoA
- dehydrogenation w/ FAD: get transenoyl CoA & less ATP
- hydration: get B-hydroxy fatty acyl CoA
- dehydrogenation w/ NAD: get B-ketoacyl CoA & more ATP
- cleavage: get acetyl CoA

Question 3

what happens after beta oxidation?

Answer 3

acetyl CoA will enter the krebs cycle
note: acetyl CoA can make more fatty acids

Question 4

difference between beta oxidation and fatty acid synthesis?

Answer 4

beta oxidation occurs in the mitochondrial matrix while fatty acid synthesis occurs in the cytoplasm

Question 5

excess glucose is converted to acetyl CoA (by glycolysis) which is then converted to fatty acids to be stored. T or F.

Answer 5

T- the body has a limited capacity to store glucose as glycogen

Question 6

what do alpha and beta cells of the pancreas do?

Answer 6

• alpha cells produce glucagon in response to hypoglycaemia/fasting state
• beta cells produce insulin (and amylin) in response to hyperglycaemia/ fed state

Question 7

major effects of glucagon on lipids?

Answer 7

• converts ATP to cAMP which activates protein kinase (phosphorylates enzymes like hormone sensitive lipase)
• activates adipose cell lipase which increases fatty acid synthesis
• inhibits storage of triglycerides in the liver
• prevents the liver from removing fatty acids from the blood

Question 8

fatty acid metabolism is mainly regulated by hydrolysis of adipose tissue by hormone sensitive lipase. T or F.

Answer 8

T

Question 9

insulin effects on fat metabolism?

Answer 9

• insulin promotes fatty acid synthesis for storage as triglycerides within adipose tissue (inhibits hormone sensitive lipase)
• decreases the utilisation of fat by the body (cuz glucose is being utilised)

Question 10

what does the hormone sensitive lipase do?

Answer 10

releases fatty acids from the adipose tissue into the circulating blood by hydrolysation

Question 11

What are the main causes of atherosclerosis?

Answer 11

• high cholesterol/high saturated fatty acids

Question 12

What does angiotensin 2 causes?

Answer 12

• hypertension (by causing vasoconstriction; also stimulates to production of aldosterone which also leads to hypertension)

Question 13

What are the 3 main ketone bodies?

Answer 13

• acetoacetic acid
• acetone
• d-B-hydroxybutyric acid

Question 14

What can happen if you have an excess amount of ketone bodies?

Answer 14

you can get ketoacidosis (pH of blood decreases); can lead to death or diabetic ketoacidotic coma

Question 15

What does glucagon do the hepatocytes (in the fasted state)?

Answer 15

• glucagon binds to the receptors on the hepatocytes which causes ATP to be converted to cAMP
• cAMP allosterically activates protein kinase which phosphorylates hormone sensitive lipase (this hydrolyses adipose tissue to get FFA)

Question 16

What effect does insulin have for fat storage during the fed state?

Answer 16

• it will inhibit the action of hormone sensitive lipase (therefore no release of FFA from adipose tissue)
• promotes glucose transport through the cell membrane into the fat cells (for storage)

Question 17

What effects other than activate HSL does glucagon have?

Answer 17

• will inhibit storage of triglycerides in the liver

Question 18

Epinephrine also has the same effects as glucagon. T or F.

Answer 18

T- it stimulates the hydrolysis of triglycerides to FFA