Lecture 11 Flashcards
True or False: a diet high in saturated fats puts you at higher risk for cardiovascular disease
False. Carbs do.
What is the difference between saturated and unsaturated fats?
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
What is the major form of energy storage in mammals?
Triacylglycerols, which make up 90% of dietary lipids
How much energy does one gram of fatty acids and one gram of sugar each carry, in kcal?
1 g fatty acids = 9 kcal
1 g sugar = 4 kcal
Why does glycogen carry less energy than lipids?
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
Rank proteins, glycogen, glucose, and fats in decreasing order of energy storage
fats > proteins > glycogen > glucose
How much glycogen is stored in muscle and liver cells?
1-2% stored in muscle
10% stored in liver cells
Describe the process of digestion of dietary lipids
- The gallbladder releases bile salts that emulsify fats into micelles, in the intestines
- Intestinal lipases degrade triacylglycerol
- Fatty acids are uptaken by mucosal cells, converting FAs into triacylglycerols (TAGs)
- TAGs are put into chylomicrons
- FAs get oxidized or reesterified for storage
Describe the parts of the chylomicron
It contains TAGs, cholesteryl esters, cholesterol, apolipoproteins, and phospholipids
What is the effect of gallbladder removal?
Difficulty in catabolizing fats because cannot emulsify lipids
Role of intestinal mucosal cells?
Convert fatty acids into TAG, package them into chylomicrons
Role of lipoproteins
Allow movement of apolar lipids through aqueous environment
How are TAGs transported throughout the body?
They cannot enter cells whole, so they must be broken down first, then they enter, then they are rebuilt again
What is VLDL and what does it do?
Very Low-Density Lipoprotein. Transports lipids from liver to tissues/body cells.
What is LDL and what does it do?
Low-density lipoprotein. Transports cholesterol straight to tissues around the body. It’s bad cholesterol
What is HDL and what does it do?
High-density lipoproteins. Moves cholesterol to the liver where it will be processed for excretion
Describe hormonal control of stored TAG mobilization
- Glucagon binds GPCR such that adenylyl cyclase + ATP make cAMP
- ATGL in the adipocyte converts TAG to DAG
- Hormone-sensitive lipase binds lipid droplets and converts DAGs to MAGs
- MAG converts to glycerol and fatty acids by MAG lipase
- Fatty acids bind serum albumin for bloodstream transport to target tissues
With which pathway does TAG mobilization overlap
Glycolysis because glycerol can be converted to glyceraldehyde 3-P
Where does fatty acid breakdown occur?
In the mitochondria
How do fatty acids get prepared to enter the mitochondria?
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
Which enzyme is key for fatty acid breakdown when preparing for entering the mitochondria?
Fatty acyl-CoA synthetase
Describe the carnitine shuttle and its role
It serves to bring FA from the cytosol into the mitochondrial matrix.
- Fatty acyl-CoA binds carnitine
- The complex goes through a transporter
- Unbind carnitine, reform fatty acyl-CoA
