Lipids Metabolism: Catabolism, Synthesis, and Transport

Comprehensive vocabulary flashcards covering lipid catabolism, fatty acid synthesis, ketone body formation, and cholesterol metabolism based on the lecture transcript.

Bile salts

Substances in the small intestine that emulsify dietary fats to facilitate their degradation by intestinal lipases.

Chylomicrons

Lipoprotein particles that transport dietary triacylglycerols from the intestinal mucosa through the lymphatic system and bloodstream to target tissues.

Apolipoproteins

Specific proteins combined with triacylglycerols to form lipoproteins for passage through the blood and lymph.

Lipoprotein lipase (LPL)

An enzyme at the target tissue that interacts with chylomicrons and VLDL to convert triacylglycerols into free fatty acids.

Hormone sensitive lipase (HSL)

An enzyme in adipocytes that is activated by glucagon to mobilize stored fats by breaking down triacylglycerols.

ATGL (Adipocyte triacylglycerol lipase)

The enzyme that initiates the sequential breakdown of triacylglycerols in adipocytes.

Serum albumin

A blood protein that binds to and transports released free fatty acids from adipose tissue to the heart, skeletal muscles, and other tissues.

Fatty acyl-CoA synthetase

An enzyme that activates fatty acids at the outer mitochondrial membrane by converting them to fatty acyl-CoA thioesters.

Carnitine shuttle

A major control point for fatty acid oxidation that facilitates the entry of fatty acyl-CoA into the mitochondria.

Carnitine acyltransferase I (CAT1/CPT1)

The mitochondrial enzyme that is allosterically inhibited by malonyl-CoA to ensure fatty acid synthesis and oxidation do not occur simultaneously.

$\beta$-oxidation

A four-step mitochondrial process (dehydrogenation, hydration, dehydrogenation, and cleavage) that removes acetyl-CoA units from the carbonyl end of a saturated fatty acyl-CoA.

Acyl-CoA dehydrogenase

The enzyme responsible for the first step of $\beta$-oxidation, involving the dehydrogenation of the $\alpha$ and $\beta$ carbons and the production of FADH2.

Enoyl CoA hydratase

The enzyme that catalyzes the second step of $\beta$-oxidation, the hydration of the trans double bond.

Thiolase (Acyl-CoA acetyltransferase)

The enzyme that catalyzes the final cleavage step of $\beta$-oxidation, releasing acetyl-CoA and a fatty acid chain shortened by two carbons.

Ketone bodies

Three chemical species (acetone, acetoacetate, and $\beta$-hydroxybutyrate) synthesized from acetyl-CoA in the liver during periods of low blood glucose or fasting.

Acetyl-CoA carboxylase (ACC)

The enzyme that catalyzes the formation of malonyl-CoA from acetyl-CoA and $HCO_3^-$, representing the first step of fatty acid synthesis.

Malonyl-CoA

A three-carbon intermediate in fatty acid synthesis that acts as the carbon donor for growing hydrocarbon chains.

Fatty acid synthase (FAS)

A cytosolic system of six enzymatic activities plus acyl carrier protein (ACP) that builds long-chain saturated fatty acids from acetyl-CoA and malonyl-CoA.

Acyl carrier protein (ACP)

The domain within fatty acid synthase that carries the growing fatty acid chain during the synthesis cycle.

Thioesterase

The enzyme domain that catalyzes the release of the final 16-carbon palmitate chain from the fatty acid synthase complex via hydrolysis.

HMG-CoA reductase

The rate-limiting enzyme of cholesterol synthesis that catalyzes the formation of mevalonate and is the target of complex regulation.

Mevalonate

A 6-carbon intermediate in cholesterol synthesis formed from HMG-CoA, requiring 2 NADPH.

Squalene

A 30-carbon non-cyclic intermediate in cholesterol biosynthesis formed by the condensation of activated isoprene units.

VLDL (Very low density lipoprotein)

Lipoproteins that carry cholesterol, cholesteryl esters, and triacylglycerols from the liver to other tissues.

LDL (Low density lipoprotein)

A cholesterol-rich lipoprotein generated from VLDL that delivers cholesterol to cells via ApoB100 binding to LDL receptors.

HDL (High density lipoprotein)

A lipoprotein that mediates reverse cholesterol transport by scavenging cholesterol from tissues and returning it to the liver.

ApoCII

The main apolipoprotein found on chylomicrons that activates lipoprotein lipase for triglyceride hydrolysis.

ApoA-I

The main apolipoprotein on HDL that activates LCAT (lecithin-cholesterol acyltransferase) to drive reverse cholesterol transport.

Atherosclerosis

A disease characterized by the accumulation of lipid plaques and foam cells in blood vessels, often linked to dysregulation of cholesterol transport.

Ketoacidosis

A life-threatening condition caused by the overproduction of ketone bodies, leading to lower blood pH and high ketone concentrations in blood and urine.