BI4.1-8 | Chemistry and Metabolism of Lipids — Glossary

A diverse group of biomolecules that are insoluble in water but soluble in organic solvents; includes fats, oils, phospholipids, steroids, and waxes

A simple lipid consisting of three fatty acids esterified to a glycerol backbone; the body's primary energy storage molecule providing ~9 kcal/g

A long-chain carboxylic acid that can be saturated (no double bonds) or unsaturated (one or more double bonds); building block of most lipids

A fatty acid that the human body cannot synthesise and must be obtained from diet; includes linoleic acid (omega-6) and alpha-linolenic acid (omega-3)

The mitochondrial metabolic pathway that breaks down fatty acids by sequentially removing 2-carbon acetyl-CoA units, generating FADH2 and NADH for ATP production

The transport system (CPT-I, translocase, CPT-II) that transfers long-chain acyl-CoA across the inner mitochondrial membrane using carnitine as a carrier

The enzyme on the outer mitochondrial membrane that transfers the acyl group from CoA to carnitine; inhibited by malonyl-CoA, the rate-limiting step of fatty acid entry

A 2-carbon unit linked to coenzyme A; the universal metabolic intermediate formed from fatty acid oxidation, glucose oxidation, and amino acid catabolism

The de novo synthesis of fatty acids from acetyl-CoA in the cytoplasm, catalysed by fatty acid synthase, producing palmitate (C16:0)

The biotin-dependent enzyme catalysing the rate-limiting step of lipogenesis: acetyl-CoA + CO2 → malonyl-CoA; activated by insulin and citrate, inhibited by glucagon and palmitoyl-CoA

The large multi-enzyme complex in the cytoplasm that catalyses the synthesis of palmitate from acetyl-CoA and malonyl-CoA using NADPH

A 27-carbon sterol essential for cell membrane fluidity, steroid hormone synthesis, bile acid formation, and vitamin D production; synthesised mainly in the liver

The rate-limiting enzyme of cholesterol synthesis that converts HMG-CoA to mevalonate; the target of statin drugs

A class of lipid-lowering drugs that competitively inhibit HMG-CoA reductase, reducing hepatic cholesterol synthesis and upregulating LDL receptor expression

An amphipathic lipid with a glycerol or sphingosine backbone, two fatty acid tails, and a phosphate-linked head group; major component of cell membrane bilayers

A sphingophospholipid (ceramide + phosphocholine) abundant in the myelin sheath of nerve fibres; deficiency of sphingomyelinase causes Niemann-Pick disease

A spherical particle with a phospholipid/apolipoprotein shell and a hydrophobic core of triglycerides and cholesterol esters, enabling lipid transport in aqueous blood

The major cholesterol-carrying lipoprotein that delivers cholesterol to peripheral tissues; elevated LDL is a primary risk factor for atherosclerosis ('bad cholesterol')

The lipoprotein responsible for reverse cholesterol transport — collecting excess cholesterol from tissues and returning it to the liver ('good cholesterol')

A protein component of lipoproteins that provides structural stability and serves as enzyme cofactors or receptor ligands (e.g. ApoB-100 for LDL receptor, ApoCII for LPL activation)

A chronic inflammatory disease of arterial walls characterised by the accumulation of oxidised LDL, foam cell formation, and fibrous plaque development, leading to luminal narrowing

A macrophage engorged with oxidised LDL cholesterol via scavenger receptors (SR-A, CD36); the hallmark cell of atherosclerotic fatty streaks

An abnormality in plasma lipoprotein levels — elevated LDL, elevated triglycerides, or decreased HDL — that increases cardiovascular disease risk

An autosomal dominant disorder caused by defective LDL receptors, resulting in markedly elevated LDL cholesterol, tendon xanthomas, and premature coronary artery disease

Water-soluble molecules (acetoacetate, beta-hydroxybutyrate, acetone) produced in the liver from acetyl-CoA during fasting or uncontrolled diabetes; serve as alternative fuel for the brain and heart