Lipid metabolism Flashcards
Where are chylomicrons formed?
small intestine
What are Lipo proteins made up of?
Composed of triglyceride, cholesterol ester (in inner core) + cholesterol, phospholipids, apolipoproteins (eg. apo-AI, -B48, -CI, -D, -E) in outer layer
_____ density lipoprotein (VLDL)
_____ density lipoprotein (IDL) / VLDL remnants
Very low (VLDL)
Intermediate (IDL)
____density lipoprotein (LDL)
____density lipoprotein (HDL)
Low (LDL)
High (HDL)
Most lipids are transported in the blood in combination with proteins as______
(Note non polar lipids in centre)
Lipoproteins
Which organ removes Chylomicron remnants?
liver
ROLES OF CHOLESTEROL?
Synthesis of membranes (stabilizes membranes especially plasma membrane)
Synthesis of bile acids (needed for digestion)
Synthesis of steroid hormones (e.g. androgens)
Synthesis of Vitamin D in skin from 7-dehydrocholesterol & UVB light.
Where do Excess LDL particles accumulate?
Excess LDL particles accumulate in artery wall and are chemically altered
What are the chylomicrons triglyceride fatty acids used for?
Used by muscle cells for ATP production
What type of type of triglycerides do VLDLs contain?
endogenous triglycerides.
What are VLDLs role?
They are transport vehicles that carry triglycerides synthesized in hepatocytes to adipocytes for storage.
What percentage of total blood cholesterol do LDLs deliver to cells throughout the body?
75%
Where do LDLs deposit cholesterol when present in excessive numbers?
smooth muscle fibers in arteries
What are HDLs role?
HDLs remove excess cholesterol from body cells and transport it to the liver for elimination (reverse cholesterol transport).
APOLIPOPROTEINS TYPES:
Apo A-I, Apo A-II, Apo A-IV
Apo B-48, Apo B-100
Apo C-I, Apo C-II, Apo C-III
Apo D
Apo E
Apo(a)
(Note Apo B is an integral apolipoprotein whereas the others are peripheral apolipoproteins)
ROLE OF APOLIPOPROTEINS:
Solubilizes highly hydrophobic lipids (Apo B)
Contains signals (ligands) to regulate movement
Enzyme Cofactors e.g. Apo A-I for lecithin cholesterol acyl transferase (LCAT), Apo C-II for lipoprotein lipase, Apo A-II activates hepatic lipase
Enzyme inhibitors e.g. Apo A-II & Apo C-III for lipoprotein lipase, Apo C-I for cholesteryl ester transfer protein
Lipid Transfer Protein
ROLES OF CHOLESTEROL
Synthesis of membranes (stabilizes membranes especially plasma membrane)
Synthesis of bile acids (needed for digestion)
Synthesis of steroid hormones (e.g. androgens, oestrogens, progesterone, glucocorticoids & mineralocorticoids)
Synthesis of Vitamin D in skin from
7-dehydrocholesterol & UVB light.
What are the four classes of lipoproteins?
Chylomicrons
VLDLs
LDLs
HDLs
How are VLDLs converted to LDLs?
via IDL
What is the order of lipoproteins with relation to increasing density? Starting with least dense.
chylomicron, VLDL, IDL, LDL, HDL
What is the order of lipoproteins with relation to increasing diameter? Starting with smallest diameter
HDL, LDL, IDL, VLDL, chylomicron
What is the order of lipoproteins with relation to increasing protein content ? starting with the smallest protein content.
chylomicron, VLDL, IDL, LDL, HDL
What is the order of lipoproteins with relation to increasing TG content ? Starting with the smallest TG content.
HDL, LDL, IDL, VLDL, chylomicron
How is Atherosclerotic Plaque Formed?
Excess LDL particles accumulate in artery wall and are chemically altered
What does Modified LDL attract and stimulate?
Modified LDL stimulate endothelial cells to attract monocytes & T cells to intima
Monocytes become macrophages. T cells and macrophages secrete ______
cytokines
Macrophages feast on LDLs and become_______ and with T cells form fatty streak
Foam cells
What does Plaque develop into?
Plaque grows as fatty streak develops into atheroma with a fibrous cap and can restrict blood flow
Usually ______ weakens and plaque ruptures and clot forms and may cause eg. unstable angina and myocardial infarction
Cap
What are the two major sources of cholesterol in the body?
dietary ingestion (exogenous) and hepatic synthesis (endogenous).
