Chapter 11 - Lipid and Amino Acid Metabolism

Where does mechanical digestion of lipids occur

mouth and stomach

where does chemical digestion occur and what facilitates it

small intestine facilitated by bile, pancreatic lipase, colipase, and cholesterol esterase

How do digested lipids promoted absorption

by forming micelles

how are short-chain fatty acids absorbed

across the intestine into the blood

how are long-chain fatty acids absorbed

as micelles and assembled into chylomicrons for release into the lymphatic system

lipids are mobilized from adipocytes by

hormone-sensitive lipase

lipids are mobilized from lipoproteins by

lipoprotein lipase

chylomicrons

transport mechanism for dietary triacylglycerol molecules via lymphatic system

VLDL

transports newly synthesized triacylglycerol molecules from the liver to peripheral tissues in the bloodstream

IDL

VLDL remnant in transitions between triacylglycerol and cholesterol transport, picks up cholesteryl esters from HDL

LDL

primarily transports cholesterol for use by tissues

HDL

is involved in the reverse transport of cholesterol

apoproteins

control interactions between lipoproteins

how is cholesterol obtained

through diet or de novo synthesis in the liver

key enzyme in cholesterol biosynthesis is

HMG-CoA reductase

LCAT

catalyzed the formation of cholesteryl esters for transport with HDL

CETP

catalyzes the transition of IDL to LDL by transferring cholesteryl esters from HDl

what are fatty acids

carb-acids with a single long chain or branched

saturated fatty acids

no double bonds between C

unsaturated fatty acid

have one or more double bonds

how are fatty acids synthesized

in the cytoplasm from acetyl-CoA transported out of the mitochondria

5 steps of fatty acid synthesis

activation, bond formation, reduction, dehydration, and reduction

how is palmitic acid formed

it is the only fatty acid humans can synthesize through the 5 steps repeated 8 times

where does fatty acid oxidation occur

in the mitochondria following transport by the carnitine shuttle

B-oxidation

uses cycles of oxidation, hydration, oxidation, and cleavage

what enzymes do unsaturated fatty acids use during cleavage

isomerase and reductase

ketone bodies

form during prolonged starvation due to escess acetyl-CoA in the liver

ketolysis

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

where does protein digestion occur

in the small intestine

when are cellular proteins catabolized

under conditions of starvation

how are amino acids used for energy

carbon skeletons are used through gluconeogenesis or ketone body formation, amino groups are fed into the urea cycle for excretion