Exam 6 Flashcards
Lipids are
Fatty acids linked to the backbone of glycerol and phospholipids by an ester bond, albumin bound
Lipid composition
Hydrocarbon chains of various lengths and carboxylic acid chain
Lipid classifications
Saturated or unsaturated, monounsaturated or polyunsaturated, cis or trans configuration
triglycerides
Contains 3 fatty acid molecules attached to 1 molecule of glycerol by ester bonds
Triglycerides containing saturated fatty acids
Solid at room temp
triglycerides containing unsaturated fatty acids
Form oils at room temp
Triglycerides from plants
Rich in polyunsaturated fatty acids
Triglycerides from animals
Mostly saturated fatty acids
Phospholipids
2 esterized fatty acids and a hydrophilic phospholipid head group attached by ester bonds, amphipathic
Most common phospholipid
Phosphatidylcholine
Cholesterol
Unsaturated steroid alcohol with 4 rings and C-H side chain, amphipathic liquid found on surface of lipid layers with phospholipids
Cholesterol converted to
Primary bile in liver, various hormones, 7-dehydrocholestrol in skin from the sunlight
Cholesterol as fuel
Cannot be used as fuel since it cannot be catabolized by most cells
Esterified form of cholesterol
Cholesteryl ester in which the OH group is conjugated by an ester bond to a fatty acid
Lipoproteins structure
Consist of lipids and proteins with amphipathic cholesterol and phospholipid on surface, hydrophobic, neutral triglyceride and cholesteryl ester in core
Chylomicron
Largest in size, lowest in density due to high lipid to protein ratio, highest amount of triacyclglycerols, cause turbidity of postprandial plasma, on top of stored plasma forming creamy layer, deliver dietary lipids to hepatic and peripheral cells
VLDL
very low density lipoprotein, 2nd highest in triacyclglycerols, major carriers of endogenous triglycerides and transport triglycerides from liver to peripheral tissues, cause most turbidity in plasma, no creamy layer
IDL
intermediate density lipoprotein
LDL
low density lipoprotein, highest in cholesteryl esters, can infiltrate extracellular space, oxidized and taken up by macrophages
HDL
high density lipoprotein due to high protein to lipid ratio
Apolipoproteins
Located on surface of lipoproteins, serve as ligands for cell receptors and as activators/inhibitors of different enzymes that regulate lipoprotein particles
Apolipoprotein A-1
Major protein on HDL
Apolipoprotein B
Principle protein on LDL, VLDL and chylomicrons
Apo B-100
Found on LDL and VLDL, a ligand for the LDL receptor and linked to lipoprotein (a)
Apo B-48
found in chylomicrons, produced by posttranscriptional editing of the apo B-100 mRNA
Apo C-I, C-II, and C-III
On chylomicrons, VLDL and HDL
Apo E
on many types of lipoproteins, functions as ligand for LDL receptor and chylomicron remnant receptor, exists in 3 forms: E2, E3, and E4
Increased production of VLDL
by liver, caused by excessive intake of carbs, saturated fatty acids, and trans fatty acids
Lipoprotein (a)
LDL-like particles with 1 molecule of apo (a) linked to apo B-100, heterogenous in size and density with plasma concentration widely distributed
elevated concentration of lipoprotein (a)
Increased risk for premature coronary heart disease and stroke due to inhibitory effect on plasminogen, a protein that enhance clot lysis
Spherical HDL
more lipid, cholesterol esters and triglycerides
Discoidal HDL
contains apo A-I to form a ring around central lipid bilayer of phospholipid and cholesterol, represents newly secreted HDL and the active form in removing cholesterol from peripheral cells
Lipoprotein metabolism
Absorption pathway, exogenous pathway, or endogenous and other pathways
Lipid absorption
Digestion of dietary lipids and absorption through passive transport via specific transporters, pass into portal circulation for short chain fatty acids but packaged into chylomicrons, re-esterified from monoglycerides and diglycerides
Triglyceride digestion
Monoglycerides and diglycerides
Cholesterol ester digestion
free cholesterol
Phospholipid digestion
lysophopholipids and bile acids
Exogenous pathway
- Chylomicrons interact with proteoglycans on surface of capillaries
- Binding of LPL to hydrolyze triglycerides on chylomicrons to produce fatty acids and glycerol
- Products (free fatty acids and glycerol) taken up as energy source
- Re-esterified into triglycerides for storage in intracellular lipid drops in fat
- Adipose cells release fatty acids from triglycerides by hormone sensitive lipase, regulated by epinephrine/cortisol/insulin
- Chylomicrons converted to chylomicron remnant after transferring lipid and apolipoproteins onto HDL
- Chylomicrons remnant taken via specific remnant receptors on liver cells
- Release fatty acids, cholesterol and AA by lysosomal enzymes
- Cholesterol and bile acids excreted into the bile with half cholesterol and almost all of the bile acids reabsorbed by the intestine
Lipid and lipoprotein levels in women
increased HDL, decreased total cholesterol and triglyceride
Lipid and lipoprotein levels in children
Decreased total cholesterol, LDL and triglycerides, no change in gender, HDL comparable to adults
Lipid and lipoprotein levels by age
Increase total cholesterol, LDL and triglyceride with age
Lipid and lipoprotein levels increasing risk of heart diseases
Increased serum cholesterol level, influenced by diet