Lipids

Question 1

The primary functions of triglycerides are __________ and __________.

Answer 1

The primary functions of triglycerides are fuel storage and plasma transport via lipoprotein particles

Question 2

Where are triglycerides stored?

Answer 2

Primarily the cytoplasm of adipose cells, also stored in muscle and small lipid bodies in many cells.

Question 3

What has more energy, triglyceride or glycogen? (per gram)

Answer 3

triacylglycerol is about twice the energy available from protein and carbohydrate per gram.

Question 4

What enzyme hydrolyzes the fatty acids from the glycerol of a triglyceride?

Answer 4

Lipase

Question 5

What are the 4 sources of Fatty Acids?

Answer 5

1) Dietary TG (intestine –> chylomicrons—-> bloodstream
2) Hepatic TG: hepatocytes make FA and TG-rich lipoprotein particles called VLDL —> bloodstream
3) Adipocytes: dump FA into blood where they bind serum albumin
4) Lipid body storage in muscle and other tissues though FAs are usually targeted for oxidation in mitochondria.

Question 6

What is lipogenesis and where does it occur?

Answer 6

Lipogenesis is process where FA are assembled into TG primarily in the liver.

Question 7

What is lipolysis is the harvesting of __________ from ______ tissue

Answer 7

Harvesting of Triglycerides from adipose tissue.

Question 8

The hormone___________ signals the well fed state and this _______ the breakdown of triglycerides, FA, ad glycogen.

Answer 8

Insulin signals the well fed state so it inhibits the breakdown of TG, FA and glycogen.
It promotes the synthesis of FA and TG.

Question 9

What stimulates the breakdown of triglycerides and fatty acids? What state is this?

Answer 9

Glucagon stimulates the breakdown of TG and FA (and glycogen) this is the hunger state.

Question 10

What hormone inhibits synthesis and storage of fatty acids?

Answer 10

Glucagon

Question 11

How is hormone-sensitive lipase (HSL) activated in adipocytes?

Answer 11

Glucagon —-> GPCR —-> AC —-> cAMP —> PKA —> Hormone sensitive lipase (HSL)

Question 12

How would a high insulin/glucagon ratio affect adipose lipolysis?

Answer 12

It would inhibit lipolysis. Insulin acts to hydrolyze cAMP which inactivates PKA and activates phosphatases that reverse PKA phosphorylation, (active HSL is inactivated).

Question 13

What is the function of HSL?

Answer 13

It helps release FA from TG in the adipocyte to the bloodstream where it binds with serum albumin.

Question 14

What is the fate of glycerol generated by lipolysis?

Answer 14

Travels to the liver and enters glycolytic pathway.

Question 15

What is the fate of fatty acids generated by lipolysis?

Answer 15

Carried by serum albumin to target organs (especially muscle) where they are transported across plasma membranes

Question 16

What organ CANNOT break down fatty acids?

Answer 16

The brain - it relies on glucose, ketone bodies and amino acids for energy

Question 17

I’m a fatty acid who wants to go into the mitochondrial matrix and prep for Beta oxidation.

FA –>(enzyme)_______ —–>acyl coA. Now I’m can go to intermembrane space of mitochondria but too big to diffuse so needs help from _________ to become _________ and go to the matrix. There, I use CPT II to ditch my chaperone __________ so I am ready for Beta oxidation in the form of Fatty Acyl CoA.

Answer 17

FA –> Fatty acyl coA synthetase —–>acyl coA. Now I’m can go to intermembrane space of mitochondria but too big to diffuse so needs help from CAT-1 (AKA CPT-1) to become fatty acyl carnitine and go to the matrix. There, I use CPT II to ditch my chaperone carnitine so I am ready for Beta oxidation in the form of Fatty Acyl CoA.

CAT-1: carnitine acyltransferase I
CPT-1: carnitine palmoitoyltransferase I.

Question 18

What is the purpose of Beta Oxidation?

Answer 18

To breakdown fatty acids (in active form of fatty acyl CoA) for energy.