Lecture 11

Question 1

True or False: a diet high in saturated fats puts you at higher risk for cardiovascular disease

Answer 1

False. Carbs do.

Question 2

What is the difference between saturated and unsaturated fats?

Answer 2

Saturated fats have no double bonds and are usually solid at room temp.

Unsaturated fats have cis-double bonds and are usually liquid at room temp

Question 3

What is the major form of energy storage in mammals?

Answer 3

Triacylglycerols, which make up 90% of dietary lipids

Question 4

How much energy does one gram of fatty acids and one gram of sugar each carry, in kcal?

Answer 4

1 g fatty acids = 9 kcal

1 g sugar = 4 kcal

Question 5

Why does glycogen carry less energy than lipids?

Answer 5

Glycogen is hydrophilic, so two grams of water bind for every 1 gram of glycogen. This reduces its energy storage to 1.33 kcal/g
Lipids are hydrophobic, so water does not bind. It has 6x more energy than glycogen

Question 6

Rank proteins, glycogen, glucose, and fats in decreasing order of energy storage

Answer 6

fats > proteins > glycogen > glucose

Question 7

How much glycogen is stored in muscle and liver cells?

Answer 7

1-2% stored in muscle

10% stored in liver cells

Question 8

Describe the process of digestion of dietary lipids

Answer 8

1. The gallbladder releases bile salts that emulsify fats into micelles, in the intestines
2. Intestinal lipases degrade triacylglycerol
3. Fatty acids are uptaken by mucosal cells, converting FAs into triacylglycerols (TAGs)
4. TAGs are put into chylomicrons
5. FAs get oxidized or reesterified for storage

Question 9

Describe the parts of the chylomicron

Answer 9

It contains TAGs, cholesteryl esters, cholesterol, apolipoproteins, and phospholipids

Question 10

What is the effect of gallbladder removal?

Answer 10

Difficulty in catabolizing fats because cannot emulsify lipids

Question 11

Role of intestinal mucosal cells?

Answer 11

Convert fatty acids into TAG, package them into chylomicrons

Question 12

Role of lipoproteins

Answer 12

Allow movement of apolar lipids through aqueous environment

Question 13

How are TAGs transported throughout the body?

Answer 13

They cannot enter cells whole, so they must be broken down first, then they enter, then they are rebuilt again

Question 14

What is VLDL and what does it do?

Answer 14

Very Low-Density Lipoprotein. Transports lipids from liver to tissues/body cells.

Question 15

What is LDL and what does it do?

Answer 15

Low-density lipoprotein. Transports cholesterol straight to tissues around the body. It’s bad cholesterol

Question 16

What is HDL and what does it do?

Answer 16

High-density lipoproteins. Moves cholesterol to the liver where it will be processed for excretion

Question 17

Describe hormonal control of stored TAG mobilization

Answer 17

1. Glucagon binds GPCR such that adenylyl cyclase + ATP make cAMP
2. ATGL in the adipocyte converts TAG to DAG
3. Hormone-sensitive lipase binds lipid droplets and converts DAGs to MAGs
4. MAG converts to glycerol and fatty acids by MAG lipase
5. Fatty acids bind serum albumin for bloodstream transport to target tissues

Question 18

With which pathway does TAG mobilization overlap

Answer 18

Glycolysis because glycerol can be converted to glyceraldehyde 3-P

Question 19

Where does fatty acid breakdown occur?

Answer 19

In the mitochondria

Question 20

How do fatty acids get prepared to enter the mitochondria?

Answer 20

Fatty acids in the cytosol get activated by ATP adenylation. The resulting fatty acyl-adenylate gets attacked by the thiol of CoA-SH, displacing AMP, forming fatty acyl-CoA

Question 21

Which enzyme is key for fatty acid breakdown when preparing for entering the mitochondria?

Answer 21

Fatty acyl-CoA synthetase

Question 22

Describe the carnitine shuttle and its role

Answer 22

It serves to bring FA from the cytosol into the mitochondrial matrix.

1. Fatty acyl-CoA binds carnitine
2. The complex goes through a transporter
3. Unbind carnitine, reform fatty acyl-CoA