Lipid and Amino Acid Metabolism (11)

MCAT Biochemistry Review 2025-2026

Mechanical Digestion

this of lipids occurs primarily in the mouth and stomach

Chemical Digestion

this of lipids occurs in the small intestine and is facilitated by bile, pancreatic-lipase, colipase, and cholesterol esterase

Micelles

digested lipids may form this for absorption or be absorbed directly

Short-chain Fatty Acids

are absorbed across the intestine into the blood

Long-chain Fatty Acids

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

Hormone-sensitive Lipase

lipids are mobilizes from adipocytes by this

Lipoprotein Lipase

lipids are mobilizes from lipoproteins by this

Chylomicrons

are the transport mechanism for dietary triacylglycerol molecules and are transported via the lymphatic system

VLDL

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

IDL

is a VLDL remnant in transition between triacylglycerol and cholesterol transport; it 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

Cholesterol

may be obtained through dietary sources or through de novo synthesis in the liver

HMG-CoA Reductase

the key enzyme in cholesterol biosynthesis

LCAT

catalyzes the formation of cholesteryl esters for transport with HDL

CETP

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

Fatty Acids

are carboxylic acids, typically with a single long chain, although they can be branched

Saturated Fatty Acids

have no double bonds between carbons

Unsaturated Fatty Acids

have one or more double bonds between carbons

Activation, Bond Formation, Reduction, Dehydration, and a Second Reduction

fatty acids are synthesized in the cytoplasm from acetyl-CoA transported out of the mitochondria. Synthesis includes five steps: _______

8; Palmitic Acid

the steps of fatty acid synthesis are repeated ____ times to form ________, the only fatty acid that humans can synthesize

Fatty Acid Oxidation

occurs in the mitochondria following transport by the carnitine shuttle

beta-Oxidation

uses cycles of oxidation, hydration, oxidation, and cleavage

Isomerase; Reducatse

unsaturated fatty acids use an __________ and an additional __________ during cleavage

Ketogenesis

ketone bodies form during a prolonged starvation state due to excess acetyl-CoA in the liver

Ketolysis

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

2/3

the brain can derive up to _____ of its energy from ketone bodies during prolonged starvation

Protein Digestion

occurs primarily in the small intestine

Catabolism of Cellular Proteins

occurs only under conditions of starvation

Carbon Skeletons of Amino Acids

are used for energy, either through gluconeogenesis or ketone body formation

Urea Cycle

amino groups are fed into this for excretion