Lipid Metabolism Flashcards

Vocabulary-style flashcards covering the digestion, absorption, transport, and utilization of lipids based on Prof. Diana Ivanova's lecture.

Lipids

Hydrophobic molecules that are compartmentalized as membrane-associated lipids or droplets of TAG in adipocytes, and transported in plasma as lipoprotein complexes.

Dietary Lipid Composition

Typically $60$ to $150\,g$ of lipids per day, consisting of $90\%$ TAG and $10\%$ C, CE, PL, and FA.

Lingual lipase

An acid stable lipase that originates from glands at the back of the tongue and functions at $pH\,3-6$.

Gastric lipase

A lipase secreted by the gastric mucosa that functions at $pH \sim 7$.

Bile salts

Derivatives of C made in the liver and stored in the gallbladder, containing a sterol ring, a side chain, and covalently attached glycine or taurine.

Pancreatic lipase

An enzyme that preferentially removes fatty acids at carbons $1$ and $3$ in TAG to produce a mixture of $2-MAG$ and FAs.

Colipase

An enzyme that binds to pancreatic lipase at a ratio of $1:1$, anchoring it at the aqueous interface and orienting the active site to the substrate.

Orlistat

An antiobesity drug that works by inhibiting gastric and pancreatic lipases.

Pancreatic cholesterol ester hydrolase

Also known as cholesterol esterase, it degrades CE into FA + C.

Mixed micelles

Clusters containing FAs, C, $2-MAG$, and bile salts that facilitate the absorption of lipids by enterocytes.

Lipid malabsorption

The loss of lipids, essential FA, and vitamins caused by blocked bile secretion, prevented pancreatic juice secretion, or defective intestinal mucosal cells.

Chylomicrons (Structure)

Lipid droplets with a center of hydrophobic TAG and CE, surrounded by a layer of PLs, non-esterified C, and a single protein molecule, apolipoprotein B-48.

Mature chylomicrons

Formed when nascent chylomicrons from the lymph enter the blood and receive Apo CII and Apo E from HDL.

Capillary LPL (Lipoprotein Lipase)

An extracellular enzyme anchored by heparan sulfate to capillary walls that breaks down TAG into FAs and glycerol.

Apo CII

An apolipoprotein that activates capillary LPL.

Apo E and Apo B-48

Apolipoproteins recognized by the receptors (R) of the hepatocytes.

Chylomicron remnants

The remainings of chylomicrons recycled by the liver through receptor-mediated endocytosis and digested by lysosomal enzymes.

Tissue-Specific FA Oxidation

FAs are oxidized for energy by skeletal muscles, liver, kidney, and heart, but NOT by the brain, RBC, or adipose tissue.

Albumin

The protein to which long-chain FAs are bound during transport in the blood.

Glycerol utilization

Glycerol can be converted to Glycerol-3-P and then to DHAP for use in glycolysis, gluconeogenesis (GNG), or TAG synthesis.