Fatty acid catabolism - Lecture 3

Question 1

What are the different fates of acetyl-CoA produced by B-oxidation?

Answer 1

Can go to CAC

Converted to ketone bodies and exported to other tissues for energy generation

Question 2

When are ketone bodies made?

Answer 2

When glucose is not available as an energy source (starvation and untreated diabetes)

Question 3

Are FAs circulatable fuel?

Answer 3

no, would cause hacock

Question 4

How can FAs be converted to fuel that can circulate the body?

Answer 4

Converted to ketone bodies

Question 5

Why can’t fatty acids be used as circulatable fuel?

Answer 5

Only so much albumin to carry it in the blood.

Question 6

What are the three ketone bodies?

Answer 6

Acetone
acetoacetate
b-hydoxybutyrate

Question 7

Which of the ketone bodies is a misnomer?

Answer 7

B-hydroxybutyrate, doesn’t have a ketone group

Question 8

What is the first enzyme involved in generating ketone bodies?

Answer 8

Thiolase, last enzyme of b-oxidation

Question 9

What does thiolase do?

Answer 9

Combines two acetyl-COA, one CoA leaves, generates acetoacetyl-CoA.

Question 10

What is done after generating acetoacetyl-CoA?

Answer 10

Converted to HMG-CoA, remove one CoA and add another.

Done by HMG-CoA synthase

Question 11

What is the enzyme/reaction after generation of HMG-COA?

Answer 11

HMG-CoA lyase, breaks acetyl-CoA and left with acetoacetate.

Acetyl-CoA leaves.

Question 12

What is the issue with generation of lots of acetoacetic acid?

Answer 12

pH of the body will decrease, become acidic.

Also, will increase osmolarity since mw is small.

Question 13

How does the osmolarity issue of acetoacetic acid get circumvented?

Answer 13

Converted (reduced) to b-hydroxybutyrate using NADH.
Two species now, two molecular particles, each of them with their own osmolarities, this will lead to a decrease in osmolarity.

Question 14

But, by converting to b-hydeoxybutyrate, the pH of the blood will still be acidic, how is this rectified?

Answer 14

Body will convert to acetone, futile.
Acidity decreases since acetone is not acidic.
Purpose is not to use as fuel, just decrease acidity.
- destroys acetoacetate to avoid acidity in the body

Question 15

When is b-hydroxybutyrate converted back to acetoacetate?

Answer 15

In cases of extreme starvation or untreated diabetes. tissues are starving of glucose.

b-hydroxy is converted to acetoacetate to produce NADH.

Question 16

How can ketone bodies be used?

Answer 16

B-ketoacyl transferase will take CoA from succinyl-CoA and acetoacetate to generate acetoacetyl-CoA.
(no energy needed since high energy compound)

Then, thiolase converts it to make two acetyl-CoA, which can go into the CAC and be completely oxidized.

Question 17

Where are ketone bodies synthesized?

Answer 17

Liver

Question 18

Which ketone bodies can be accepted by the tissues?

Answer 18

B-hydroxy and acetoacetate

Question 19

What is a simple measure of diabetes?

Answer 19

Measure ketone bodies in the blood and urine.

If high - diabetic

Question 20

What is ketosis?

Answer 20

High concentration of ketone bodies in the blood and urine

Question 21

Why does a untreated diabetics breath smell like acetone?

Answer 21

Due to high concentration of acetoacetate, this is converted to acetone, which is water soluble, which goes out of the lungs, so breath smells like acetone.

Question 22

What are symptoms of diabetics?

Answer 22

Thirsty all the time and goes to the bathroom a lot

Question 23

Explain why diabetics are always thirsty and go to the bathroom often.

Answer 23

Excess ketone bodies are made in untreated diabetics.
This causes a decrease in blood pH.
So, to balance the pH, the body uses the sodium-bicarbonate buffer system.
This takes out water and salts from the tissues to dilute and increase the pH, This all gets secreted in the urine, causing increased bathroom frequency.

Since, water and salts are taken out of the tissues, they are thirsty, inducing thirst and drinking behaviour.

Question 24

If diabete’s is extreme, you can smell acetone in the person’s breath, why?

Answer 24

o If have mild ketosis, ketone bodies utilized, don’t make acetone since acidity is low

But, if makings lots of ketone bodies, liver will think there is too much acidity and convert acetoacetate to acetone, in that case, see acetone made and, very soluble in water and air, so blood goes to lungs, goes out there into the lungs