question

Example of Phospholipid is

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Dipalmitoylphosphatidylcholine (DPCC) or dipalmitoyllecithin

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Dipalmitoylphosphatidylcholine (DPCC) or dipalmitoyllecithin

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is the major component of surfactant in the lungs (80%).
It is produced by type II epithelial cells and prevents atelectasis
Decreases surface tension of the fluid layer of the lung.
Surfactant also contains: PG, PI and 2 surfactant proteins.

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Phosphatidylethanolamine Synthesis occur in

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liver
brain

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Phosphatidylethanolamine-N-methyltransferase

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occurs in liver only

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Phospholipase A1

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inhibited by glucocorticoid
can remove fatty acids selectively from carbon 1 of the glycerol backbone.

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•Phospholipase A2can

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remove fatty acids selectively from carbon 2 of the glycerol backbone.

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Roles of Cholesterol:

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Membrane structure
A precursor for the synthesis of the steroid hormones and bile acids.

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Both dietary cholesterol and that synthesized de novo are transported through the circulation in ....?

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lipoprotein particles

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The form in which cholesterol is stored in cells

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cholesteryl esters,

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•The synthesis and utilization of cholesterol must be tightly regulated in order to prevent:

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over-accumulation
abnormal deposition within the body.

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The abnormal deposition of cholesterol and cholesterol-rich lipoproteins in the coronary arteries cause:

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Atherosclerosis

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Most plasma cholesterol is in a/an

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esterified form

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Most plasma cholesterol is in an esterified form, with a fatty acid attached at....?
This makes it even more hydrophobic then free cholesterol.

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C-3

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All carbon atoms of cholesterol are derived from ?

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acetate

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In Cholesterol Biosynthesis, reducing power in the form of NADPH is provided mainly by glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase of the ..........pathway????

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pentose phosphate pathway

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In Cholesterol Biosynthesis, reducing power in the form of ............ is provided mainly by glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase of the pentose phosphate pathway????

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NADPH

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Cholesterol Biosynthesis has ....major steps

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5

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•All the reduction reactions of cholesterol biosynthesis use ........as a cofactor.

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NADPH

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In Cholesterol Biosynthesis, Acetyl-CoA units are converted to mevalonate by a series of reactions that begins with the formation of .....?

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HMG-CoA.

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In Cholesterol Biosynthesis, HMG-CoA is converted to mevalonate by ....?

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HMG-CoA reductase

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What is the rate limiting step of cholesterol biosynthesis???

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The reaction catalyzed by HMG-CoA reductase

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HMG-CoA reductase is most active in

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in the dephosphorylated state

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•What activates HMG-CoA reductase activity??

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Insulin

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•Statins

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competitive inhibitors of HMG-CoA Reductase.

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Drug Therapy for Dyslipidemia

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–Simvastatin
–Pravastatin
–Lovastatin

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Statins exert their major effect by

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reduce LDL levels

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Statins affect blood cholesterol levels by

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inhibiting cholesterogenesis in the liver
which results in increased expression of the LDL receptor gene
The greater number of LDL receptors on the surface of hepatocytes results in increased removal of LDL from the blood thereby lowering LDL-C levels

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The greater number of LDL receptors on the surface of hepatocytes results in

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increased removal of LDL from the blood
thereby lowering LDL-C levels

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The most abundant bile acids in human bile are

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chenodeoxycholic acid (45%)
cholic acid (31%).

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chenodeoxycholic acid (45%) and cholic acid (31%) are

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primary bile acids

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•Within the intestines the primary bile acids are acted upon by bacteria and converted to

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the secondary bile acids

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Primary bile acid is converted to secondary bile acid

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deoxycholate (from cholate
lithocholate (from chenodeoxycholate).

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•In liver the carboxyl group of primary and secondary bile acids is conjugated via ..........bond to either glycine or taurine before their being resecreted into the bile canaliculi.

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an amide bond

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Bile acids perform 4 physiologically significant functions:

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1. Eliminate of excess cholesterol.
2. Solubilize cholesterol in the bile, thereby preventing the precipitation of cholesterol in the gallbladder.
3. Facilitate the digestion of dietary triacylglycerols
4. Facilitate the intestinal absorption of fat-soluble vitamins.

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Dietary cholesterol is transported from the small intestine to the liver within....?

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chylomicrons

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Cholesterol synthesized by the liver, and excess dietary cholesterol in the liver are transported in the serum within ....?

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LDLs

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cholesterol is excreted in the bile as......... or as .............following conversion to bile acids in the liver.

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free cholesterol
bile salts

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•Reverse cholesterol transport allows peripheral cholesterol to be returned to the liver in .....?

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HDLs

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Cholesterol found in plasma membranes can be extracted by ........ and esterified by the ..............

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HDLs
HDL-associated enzyme LCAT

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•The liver synthesizes .......... and these are converted to ........... through the action of endothelial cell-associated lipoprotein lipase.

answer

VLDLs
LDLs

Exam 3 Biochem-Lecture 29 – Flashcards

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