Lipids Flashcards
(35 cards)
What are the main functions of lipids in the human body?
Energy storage, membrane structure, and precursors for signaling molecules (e.g. prostaglandins, leukotrienes, thromboxanes).
What molecule is the precursor for prostaglandins, leukotrienes, and thromboxanes?
Arachidonic acid (D4 derivative of eicosanoic acid).
What are fatty acids the building blocks for?
Triglycerides, phospholipids, and eicosanoids.
Describe the basic structure of a fatty acid.
Long hydrocarbon chain with a terminal carboxyl group.
What is the typical chain length of fatty acids?
Between 14 and 20 carbons, often even-numbered.
What is the effect of double bonds on fatty acids?
Double bonds lower the melting point and prevent tight packing.
What does the shorthand notation 18:2Δ5,8 mean?
An 18-carbon fatty acid with two double bonds at positions 5 and 8.
What is a triglyceride?
A glycerol molecule esterified with three fatty acids; main energy storage lipid.
Why are triglycerides efficient for energy storage?
They are hydrophobic, compact, and store ~38 kJ/g.
What are phospholipids composed of?
Glycerol, 2 fatty acids, phosphate group, and a polar head group.
What is the function of phospholipids?
Major component of cell membranes.
What roles does cholesterol play in the body?
Membrane stability, precursor to steroid hormones and bile acids, and involved in lipid transport.
What are lipoproteins?
Complexes that transport lipids in the blood.
What enzyme is required to use glycerol for triglyceride synthesis in liver and kidney?
Glycerol kinase.
What are the two sources of glycerol-3-phosphate?
From glycolysis (DHA-P) or direct phosphorylation of glycerol.
Which enzyme reduces DHA-P to G3P?
Glycerol-3-phosphate dehydrogenase.
What must happen before fatty acid oxidation begins?
Fatty acids must be activated and transported into mitochondria.
How are fatty acids activated?
By linking them to Coenzyme A in the cytosol.
How are fatty acids transported into the mitochondria?
By forming acyl-carnitine, transported via the carnitine carrier protein.
Where does β-oxidation occur?
In the mitochondria (and peroxisomes for very long chains).
What are the steps of β-oxidation?
Dehydrogenation, hydration, NAD+-dependent dehydrogenation, and cleavage to form Acetyl-CoA.
What are the key oxidizing agents in β-oxidation?
NAD+ and FAD.
Where does Acetyl-CoA go after β-oxidation?
To the TCA cycle for complete oxidation.
What regulates fatty acid oxidation?
Availability of free fatty acids and inhibition by Malonyl-CoA.
