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17 Cards in this Set
- Front
- Back
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Describe how the body digests TAGs. |
Medium sized TAGs: broken down by lingual and gastric lipase to MAGs and FFAs.
Large TAGs: broken down by pancreatic lipase (esterase). Emulsification of dietary lipids in the small intestine is carried out by bile salts (e.g. glycocholic acid). |
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What is dietary lipids made up of?
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90% TAGs, the rest is made up of cholesterol, cholesteryl esters, phospholipids, and FA's.
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What enzyme is responsible for cholesteryl ester degradation? Phospholipid degradation?
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Cholesterol esterase.
Phospholipase A2. |
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What peptide hormone controls lipid digestion? |
CCK (from I cells). Causes contraction/release of bile from gall bladder. Decreases gastric motility.
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What peptide hormone is released in response to low pH in the intestines?
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Secretin (from S cells) causes the pancreas and the liver to release a watery solution rich in bicarbonate.
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In the enterocytes, fatty acids are activated by ________ to fatty acyl-CoA.
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Fatty acyl-CoA synthetase (thiokinase). Fatty acyl-CoA is then converted to TGs by MAG-acyltransferase and DAG-acyltransferase.
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Chylomicrons package up the TAGs, cholesteryl esters, and phopholipids in the ER of the enterocytes. What are the chylomicrons released into and where do they go?
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Chylimicrons are released by exocytosis into the lacteals which travel to the thoracic duct and enter the left subclavian vein. Apo E on chylomicrons is recognized by the liver.
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What apolipoprotein on chylomicrons activates lipoprotein lipase?
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Apo C-II
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Give four uses of fatty acids:
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1) Esterified FA (TAGs) is the major energy reserve of the body.
2) FA are oxidized (liver, muscle) for energy. 3) Structural components of membrane lipids (glycolipids, phospholipids). 4) FA are precursors for prostaglandins |
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How is unesterified fatty acids are transported in the blood? |
Bound to albumin. 90% of FAs are found in the esterified form (cholesterol, TGs, phospholipids)
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What are the two essential dietary fatty acids?
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Linoleic acid (omega-6, because the first double bond is at the 6th carbon from the omega carbon. Omega carbon is the carbon of the terminal methyl group). Linoleic is converted to arachidonic acid.
Linolenic acid (omega-3) |
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De novo fatty acid synthesis occurs primarily in the liver and mammary glands and to a lesser extent in adipose tissue. The first step is the transfer of acetate units from mitochondrial acetyl CoA to the cytosol. How does this occur?
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Acetyl CoA and oxaloacetate is condensed to citrate which is able to cross the mitochondrial membrane.
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What is the rate-limiting step in fatty acid synthesis? What hormones control its activity?
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Carboxylation of acetyl CoA to form malonyl CoA via acetyl CoA carboxylase.
Insulin dephosphorylates acetyl CoA carboxylase thus making it activated. Glucagon and epinephrine phosphorylate/inactivate acetyl CoA carboxylase. |
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What is the 16 carbon FA product of fatty acid synthesis?
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Palmitate
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ATP and what cofactor are needed for fatty acid synthesis? What is the source of this cofactor? What else is this cofactor used for?
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NADPH comes form the hexose monophosphate pathway and from oxidation/carboxylation of malate to pyruvate. NADPH is used for lipid synthesis, by cytochrome p450, and to neutralize ROS.
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Where does glycerol phosphate (the backbone of TAGs) come from?
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Glucose to G6P to F6P to F1,6BP to glyceraldehyde 3-P to dihydroxyacetone phosphate (DHAP) which is reduced to glycerol phosphate.
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Where does beta-oxidation occur in the cell? How do fatty acids access this area of the cell?
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Mitochondrial matrix. Carnitine carries the FA from the cytosol to the matrix.
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