Lipid and Amino acid metabolism

Micelles

clusters of amphipathic lipids

vital in digestion, transport, and absorption of a lipid

Factors that facilitate lipid digestion

• bile salts

• pancreatic lipase

• colipase

• cholesterol esterase

Hormone-sensitive lipase

hydrolyzes triacylglycerols to yield fatty acids and glycerol

Chylomicrons

transport dietary triacylglycerols, cholesterol, and cholesteryl esters to other tissues

Very-Low-Density-Lipoprotein (VLDL)

transport of triacyclglycerols and fatty acids from liver to tissues

Intermediate-density Lipoprotein

Picks up cholesteryl esters from HDL to become LDL

Low-Denisty Lipoprotein

deliver cholesterol to tissues

High-Density Lipoprotein

cleaning of extra cholesterol in the blood vessels for excretion

“good” cholesterol

Apolipoproteins

control interactions between lipoproteins

Where are lipoproteins primarily formed

Intestines and liver

Regulation of cholesterol synthesis

Inhibitors: cholesterol

Promoters: Insulin

Bond configuration for saturated and unsaturated fatty acids

saturated: no double bonds

Unsaturated: one or more double bonds

Where does fatty acid synthesis take place

The liver

Rate limiting enzyme for fatty acid synthesis

Acetyl-CoA carboxylase

The only fatty acid that humans can synthesize de novo

Palmitate

B-Oxidation four steps

1. oxidation of acetyl-CoA to form double bond

2. Hydration of double bond to form hydroxyl group

3. Oxidation of hydroxyl group to form Carbonyl

4. Splitting of carbonyl into shorter acyl-CoA and acetyl-CoA

Ketone bodies

acetoacetate and 3-hydroxybutyrate

the body metabolizes ketone bodies in times of starvation for energy

Ketogenesis

formation of ketone bodies which occurs in the liver

• occurs when there is excess acetyl-CoA

Ketolysis

regenerates acetyl-CoA for use as an energy source in peripheral tissues

Where does protein digestion primarily take place?

the small intestine