Lipids and Laboratory Methods for Lipoproteins

Comprehensive vocabulary flashcards covering lipid classifications, biochemistry, laboratory measurement methods, and associated clinical disorders based on the lecture material.

Lipids

Primary source of fuel that provide stability to cell membranes and allow for transmembrane transport; they are insoluble in water but soluble in organic solvents like chloroform and ether.

Lipoproteins

Spherical lipid and protein complexes with a liquid core of triglycerides and cholesterol esters and an outer shell of phospholipids, protein, and free cholesterol used to transport lipids in the blood.

Fatty Acids

Short, medium, and long chains of molecules that serve as major constituents of triglycerides and phospholipids and provide a substance for gluconeogenesis.

Saturated Fatty Acids

A type of fatty acid that acts as a building block for triglycerides and phospholipids and serves as a source of metabolic energy.

Phospholipids

The most abundant lipid derived from phosphatidic acid, formed from two fatty acids and phosphorylated glycerol, creating an amphipathic molecule with polar and nonpolar ends.

Sphingomyelin

An essential phospholipid component of the cell membranes of red blood cells and the nerve sheath.

Lecithin (Phosphatidyl choline)

The most prevalent form of phospholipid in the body, accounting for 70% of total phospholipids.

Surfactant

A substance composed of phospholipids that alters fluid surface tension in the alveolar space to prevent alveolar collapse during expiration.

Neonatal Respiratory Distress Syndrome (RDS)

A condition caused by a deficiency of surfactant in newborns.

Lecithin/Sphingomyelin (L/S) Ratio

A test used to estimate the status of fetal lung maturation by evaluating pulmonary surfactant in amniotic fluid.

Cholesterol

An unsaturated steroid alcohol containing four rings and a single $C-H$ side chain; it is a vital structural component of cell membranes and a precursor of steroid hormones and bile acids.

Cholesterol Esters (CE)

The neutral form of cholesterol bound to fatty acids, comprising 70% of total cholesterol, found in the center of lipid drops and lipoproteins.

Free Cholesterol (FC)

A polar non-esterified alcohol comprising 30% of total cholesterol, available for membrane, hormone, and bile acid synthesis.

Lecithin-Cholesterol Acyl Transferase (LCAT)

An enzyme that esterifies cholesterol in plasma by transferring fatty acids from lecithin to cholesterol.

Acyl Cholesterol Acyl Transferase (ACAT)

A microsomal enzyme responsible for the re-esterification of excess cholesterol within cells.

HMG-CoA reductase

The enzyme that reduces $HMG-CoA$ to mevalonate during the second stage of cholesterol biosynthesis.

Salkowski Reaction

A chemical method for measuring cholesterol that produces a red colored end product called Cholestadienyl Disulfonic Acid.

Liebermann-Burchardt Reaction

A chemical method for measuring cholesterol that produces a green colored end product called Cholestadienyl Monosulfonic Acid.

Abell-Levy and Brodie Method

The CDC reference method for cholesterol measurement involving hydrolysis with alcoholic $KOH$, hexane extraction, and colorimetry using L-B reagent.

Triglycerides (Triacylglycerol)

The main storage lipid in humans, containing three molecules of fatty acids and one molecule of glycerol, providing insulation and energy.

Chylomicrons (CM)

The largest and least dense lipoproteins ($< 0.95 kg/L$) produced in the intestine that deliver dietary lipids to hepatic and peripheral cells.

VLDL (Very Low Density Lipoprotein)

Also known as pre-beta-lipoprotein, it is secreted by the liver to transport endogenous triglycerides to peripheral tissues.

LDL (Low Density Lipoprotein)

Also known as beta-lipoprotein, it is the most atherogenic lipoprotein and the primary target of cholesterol-lowering therapy.

HDL (High Density Lipoprotein)

Also known as alpha-lipoprotein, it is the smallest and most dense lipoprotein responsible for reverse cholesterol transport from tissues back to the liver.

IDL (Intermediate Density Lipoprotein)

A product of VLDL catabolism, often called a VLDL remnant, that is eventually converted to LDL.

Lipoprotein (a) [Lp(a)]

A 'sinking pre-B lipoprotein' variant of LDL that contains Apo (a) linked to Apo $B-100$; it is an independent risk factor for atherosclerosis.

Lipoprotein X (LpX)

An abnormal lipoprotein found in obstructive jaundice and LCAT deficiency, acting as a sensitive indicator of cholestasis.

Apolipoprotein A-1

The major protein found in HDL that activates LCAT and is considered antiatherogenic.

Apolipoprotein B-100

The major protein found in LDL, VLDL, and IDL, associated with an increased risk of coronary artery disease.

Friedewald Equation

A formula used to calculate LDL cholesterol: $LDLc = Total cholesterol - (HDLc + VLDL)$, where $VLDL = TG \div 5$ in $mg/dL$.

DeLong Equation

An equation more accurate than Friedewald when triglycerides are above $400 mg/dL$, where $VLDL = TG \div 6.5$.

Standing Plasma Test

A screening test where plasma is refrigerated overnight; chylomicrons appear as a floating 'cream' layer, while excessive VLDL causes turbidity.

Dyslipidemias

Diseases associated with abnormal lipoprotein levels, categorized into hyperlipoproteinemias (elevated) and hypolipoproteinemias (decreased).

Tangier Disease

A hypolipoproteinemia characterized by the absence of HDL and very low levels of Apo $A-I$ and Apo $A-II$ due to a mutation in the $ABCA1$ gene.

Abetalipoproteinemia

Also known as Bassen-Kornzweig syndrome, a condition where LDL and Apo $B-100$ are absent, and triglycerides are nearly undetectable.

Atherosclerosis

The narrowing of arteries due to plaque build-up on arterial walls caused by the deposition of cholesterol and triglycerides.

Sitosterolemia

An extremely rare autosomal recessive disorder where plant sterols (phytosterols) are absorbed and accumulate in plasma and tissues.

Chylomicron Retention Disease

Also known as Anderson's disease, it presents in childhood with fat malabsorption and low levels of plasma lipids.