Quiz 3: Lipids and Lipoproteins Flashcards
Triglyceride Transport (Exogenous Transport)
Via chylomicrons and VLDL
Dietary lipids absorbed and assembled with ApoB-48 into chylomicrons which are broken down in circulation to triglyceride and chylomicron remnants for metabolism or recycling through the liver.
Lipoprotein lipase frees Free fatty acids and glycerol from Triglycerides
Triglyceride Metabolism
Release of Fatty Acids from cells for energy, recycling of glycerols into triglycerides
Lipase, lipoprotein lipase, epinephrine and cortisol break down triglycerides
Cholesterol Forms
Unsaturated steroid alcohol when esterified: fatty acid attached with ester bond
Free form is unsterified
Cholesterol Precursors
Bile acids, steroid hormones, and Vit D
Cholesterol Transport
LDL is primary carrier
Lipoprotein (Definition)
Molecules that combine insoluble dietary lipids with water soluble proteins for transport; micelles are spherical with an inner core of neutral fat
Chylomicrons (Definition)
Largest lipoprotein with lowest density, form in intestines to transport triglycerides; normally enter circulation and are metabolized then taken to the liver to be further modified
They are 86% Triglyceride
VLDL
Carries triglycerides synthesized in liver (endogenous transport); normally secreted into blood from liver (after being packaged in VLDL) to be metabolized in peripheral tissues into triglycerides and VLDL remnants or intermediate density lipoproteins for use in metabolism or recycling through the liver
Apo B is the major protein
IDL
intermediate-density-lipoprotein
Transitional form between VLDL and LDL, they carry endogenous triglycerides and cholesterol esters
LDL
Major cholesterol carrier, largely endogenous cholesterol
Easily taken up by cells, and are thus assoc. with athlerosclerosis
Normally brings cholesterol to peripheral cells for membrane synthesis and hormone creation –> Infiltrate into extracellular space of vessel wall and cleared by macrophages (Macrophages with too much lipid may turn into foam cells which may be plaque precursors)
Apo B is the major protein
HDL
Made in the liver and intestine of recycled chylomicron and VLDL molecules; normally removes excess cholesterol from peripheral tissues (antiatherogenic effect)
Apo A-1 is the major protein
Lp(a)
Mostly cholesterol esters, phospholipids, and apolpoprotein (a)
Elevated levels are assoc. with coronary heart disease, heart attack, and cerebrovascular disease
Cholesterol Ranges
Total: < 200, high: >240
HDL: > 60, at risk for heart disease: < 40
LDL: < 100, High: 160-189
Lipid soluble Vitamins
A,D,E, and K
Time needed to utilize different energy sources
Glucose - minutes
Glycogen- 1 day
Protein - 10 day
Lipids - 30-40 days with water
Functions of cholesterol
Precursor of steroid hormones
Cell membrane component
Precursor of bile salts
Apolipoprotein
The protein portion of the transport molecule, free of the lipid component
Apolipoprotein A: major portion of HDL
Apolipoprotein B: major portion of LDL
Apolipoprotein C: major protein of VLDL and Chylomicrons
large: apoB (B-48 and B-100): atherogenic
smaller: apoA-I, apoC-II, apoE
Cholesteryl ester
A compound of cholesterol and a fatty acid
Plasma Lipid Components
Cholesterol, Trigylcerides, Phospholipids, and non-esterified fatty acids
Normal proportions of lipoproteins
LDL: 60-70%
HDL: 20-35%
VLDL: 5-12% (Very Low Density Lipoproteins)
Triglycerides Function
Primary form of lipid storage
Cholesterol Function
Important in cellular physiology, a precursor to Steroid hormones
LDL takes it to cells, HDL takes it out of cells
Chylomicrons Function
Dietary (exogenous) triglycerides
VLDL Function
Endogenous triglycerides
LDL Function
Cholesterol to cells
HDL Function
Cholesterol out of cells
Triglyceride Testing Methods
Enzymes are the best method, usually involving freeing glycerol by lipase
HDLc
Direct/Homogeneous assays measure without pretreatment
Indirect methods remove chylomicrons, VLDL, and LDL through precipitation
LDLc
Direct/Homogeneous assays measure without pretreatment
Friedewald Method
Calculation of LDLc and VLDLc when Triglycerides are
Triglyceride Structure
One glycerol with 3 fatty acids attached via ester bonds, 95% of all fats in adipose tissue are trigycerides
