Lipids 2

Question 1

Where does the fatty acid metabolism occur?

Answer 1

In the mitochondria (catabolism by B-oxidation, some chain lengthening)

Question 2

What is the conversion in the oxidative process?

Answer 2

Fatty acid to acetyl CoA to citric acid cycle to energy

Question 3

What type of process is the acetyl CoA conversion?

Answer 3

Removal of two carbons cycle

Question 4

Steps of oxidation?

Answer 4

1. Activated FA oxidised; introduce a double bond (dehydrogenase enzyme, redox cofactors FAD to FADH2)
2. Double bond hydrated (introduces OH group- catalysed by hydratae family enzyme)
3. Hydroxyl group oxidised to ketone (dehydrogenase enzyme; redox cofactor NAD reduced to NADH)
4. FA cleavage (acetyl CoA and FA that is two carbons shorter, thiolase enzyme, CoA as cofactor)

Question 5

What in regards to fatty acids mirror each other in chemical reactions?

Answer 5

Fatty acid degradation and synthesis

Question 6

What are highly concentrated stores of metabolic energy because they’re reduced?

Answer 6

Triacylglycerols

Question 7

What are lipids ingested as and what must they be degraded to, for absorption across the intestinal epithelium?

Answer 7

Ingested as triacylglycerols, must be degraded to fatty acids

Question 8

What happens to triacyglycerols in the intestinal lumen?

Answer 8

They’re incorporated into lipid globules composed of bile salts, amphiathic molecules synthesised from cholesterol in the liver and secreted from the gall bladder

Question 9

What catalyse the hydrolysis of bonds between the fatty acyl group and glycerol of triacylglycerols?

Answer 9

Lipases from the pancreas

Question 10

What three stages of processing must occur for the utilisation of fatty acids as fuel?

Answer 10

1. Lipids must be mobilised; triacylglycerols are degraded to FFAs and glycerol which are released from adipose tissue and transported to the energy-requiring tissues
2. At these tissues, the fatty acids must be activated and transported into mitochondria for degradation
3. The fatty acids are broken down in a step by step fashion into acetyl CoA, which is then processed in the citric acid cycle

Question 11

What transports fatty acids and why?

Answer 11

Serum albumin (as not soluble in water)

Question 12

What is lipolysis?

Answer 12

When triacylglycerols are hydrolysed by hormone-stimulates lipases in adipose tissue

Question 13

Steps of lipolysis?

Answer 13

1. Hormones trigger 7 TM receptors that activate adenylate cyclase
2. Increases cyclic AMP stimulates protein kinase A, which phosphorylates triacylglycerol lipase/hormone-sensitive lipase
3. Triacylglycerols, by releasing fatty acid from triacylglycerol, forming diacylglycerol- which is converted into a free fatty acid and monoacylglycerol by hormone sensitive lipase
4. Monoacylglycerol lipase completes the mobilisation of fatty acids wothvthe production of a free fatty acid and glycerol. Thus, epinephrine and glucagon induce lipolysis

Question 14

What generates fatty acids and glycerol?

Answer 14

Lipolysis

Question 15

What must happen to fatty acids for it to be degraded?

Answer 15

Must be activated and transported into mitochondria

Question 16

What activates a fatty acid for transport?

Answer 16

The formation of a thioester linkage to coenzyme A

Question 17

What drives the formation of a thioester linkage between the carboxyl group of a fatty acid and the sulphudryl group of CoA?

Answer 17

ATP

Question 18

Where does the activation of fatty acids occur?

Answer 18

On the outer mitochondrial membranes

Question 19

What carries a long-chain activated fatty acid into the mitochondrial matrix?

Answer 19

Carnitine

Question 20

What are fatty acids broken down into and what is it processed in?

Answer 20

Broken down into acetyl CoA and processed in the citric acid cycle

Question 21

What is the b-oxidation pathway?

Answer 21

Saturated acyl CoA is degraded by a recurring sequence of 4 reactions;

Question 22

Four steps of B-oxidation?

Answer 22

1. Oxidation (FAD)
2. Hydration
3. Oxidation (NAD+)
4. Thiolysis (coenzyme A)

Question 23

What shortens the fatty acid chain?

Answer 23

Two carbons and acetyl CoA, NADH and FADH2 are generated in each round of fatty acid oxidation

Question 24

What does the oxidation of FA containing double bonds require?

Answer 24

Additional steps ( as do the oxidation of fatty acids containing an odd number of carbon atoms)

Question 25

What’s the reaction sequence for the degradation of fatty acids?

Answer 25

Acyl CoA dehydrogenase
Enoyl CoA hydratase
L-3-hydroxyacyl CoA dehydrogenase
B-ketothiolase

Question 26

What is the oxidation of palmite and how much ATP does it yield?

Answer 26

Palmitoyl CoA + 7FAD+ 7NAD + 7CoA + 7H2O to 8 acetyl CoA + 7FADH2 + 7NADH + 7H

106

Question 27

When are ketone bodies formed?

Answer 27

From acetyl CoA when fat breakdown predominates

Question 28

What are a major source of fuel in some tissues?

Answer 28

Ketone bodies (used when starving)