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43 Cards in this Set
- Front
- Back
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Definition of a lipid |
soluble in organic solvents (ether, benzene, chloroform, etc |
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Major classes of lipid (important in nutrition) |
1. Fatty Acids
2. Triacylglycerols
3. Sterols |
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What is a fatty acid |
Carboxylic acid with hydrocarbon chain between 4 and 38 carbons |
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Difference between unsaturated and saturated fatty acids |
Unsaturated = 1+ double bonds
Saturated = 0 double bonds |
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6 important fatty acids and their lipid number |
1. Butyric - 4:0 2. Palmitic - 16:0 3. Steric - 18:0 4. Oleic - 18:1 (C-9) 5. Linoleic - 18:2 (C-9, C-12) 6.Linolenic - 18:3 (C-9, C-12, C-15) |
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Regular and Omega nomenclature for linoleic and linolenic acid |
linoleic [18:2 (n-6)] or 18:2 all cis-9,12
linolenic [18:3 (n-3)] or 18:3 all cis-9,12,15 |
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What is a CLA |
Conjugated Linoleic Acid
isomers of linoleic acid - all 18:2 with alternating single/double bonds
intermediates of biohydrogenation in the rumen |
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What are mono-,di-, and triacylglycerols |
Esters of glycerol and fatty acids (1,2, or 3) |
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What are glycerophospholipids |
Glycerol with 2 fatty acids and phosphate with polar head group
major component of cell membranes (phospholipid bi-layer) |
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What are sterols |
Fused carbon ring
Cholesterol is most abundant sterol in animal tissues - component of cell membranes
also - bile acid, progesterone, estrogen etc |
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What is the function of lipids |
energy! calorically dense and highly digestible (>80%) |
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Which lipids are unconditionally essential for animals |
alpha-linolenic and linoleic fatty acids |
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What is the precursor for n-3 PUFA's |
alpha-linoleic acid
Eicosapentanoic acid (EPA) Docosahexaenoic acid (DHA) |
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What is the precursor for the n-6 PUFA |
linolenic acid
Arachidonic Acid (AA) |
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______ and ______ are precursors of the signaling molecules eicosanoids |
EPA and AA |
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In cats, ______ are non-conditionally essential |
AA |
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What is the most abundant n-3 PUFA in the brain |
DHA |
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What is the carrier of fat-soluble vitamins |
micelle's - formed by fatty acids they surround fat-soluble vitamins and facilitate absorption in the small intestine |
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Where does digestion of lipids begin |
duodenum |
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What are the stops of lipid digestion and absorption |
1. bile enters duodenum from gall bladder and emulsifies lipid 2. Pancreatic and intestinal lipases hydrolyze triacylglycerols to glycerol, FFA and monoacylglycerols 3. mixed micelle's formed from FFA, monoacylglycerols, cholesterol and fat-soluble vitamins |
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Where are micelle's absorbed |
jejunum and ileum |
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Origin, substrate and end products of pancreatic lipase |
pancreas, triglycerides, monoglyceride + 2 fatty acids |
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Origin, substrate and end products of intestinal lipase |
Sm. intestine, triglycerides, glycerol + fatty acids |
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Exogenous pathway of lipid transport and deposition |
1. Intestinal mucosal cell - chylomicrons 2. Lymphatic system 3. Bloodstream - FA and glycerol 4. Adipose and skeletal muscle 5. Liver (left overs) |
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Endogenous pathway of lipid transport and deposition |
1. Liver - VLDL 2. Blood - FA released 3. Adipose - FA taken up for storage 4. Liver - VLDL to LDL 5. Bloodstream - LDL 6. Peripheral tissue - take up LDL |
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What is the reverse cholesterol pathway |
HDL exports lipid and cholesterol from peripheral tissue back to liver |
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List the main lipoproteins in order of lowest to highest density |
Chylomicron (lowest) VLDL LDL HDL (highest) |
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What is "good" cholesterol and what is "bad" Why? |
LDL = bad - transports cholesterol to peripheral tissue
HDL = good - transports cholesterol from peripheral tissue to liver |
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Steps of Fatty Acid Biosynthesis |
1. Acetyl-CoA and Malonyl-CoA to Acetyl-ACP and Malonyl ACP 2. The two condense and Acetyl ACP is elongated by 2 C 3. Cycle repeats until Palmitic Acid formed |
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What is the definition of elongation and desaturation |
Elongation = Add + carbons (palmitate to sterate)
Desaturation = Add + double bonds (Oleate to Linoleate) |
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Steps of triacylglycerol biosynthesis |
1. Glycerol phosphorylated (Glycerol 3-Phosphate) 2. 2 Fatty Acids added (Phosphatidic Acid) 3. 3rd fatty acid added (triacylglycerol) or polar head group (glycerophospholipid) |
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Steps of fatty acid catabolism or beta-oxidation |
1. Fatty acid is cleaved in 2 C units (acetyl-CoA)
2. Acetyl-CoA enters citric acid cycle |
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Steps of ketone metabolism |
Acetyl-CoA to Acetoacetyl-CoA to HMG CoA to Acetoacetate to either acetone of Beta-D-Hydroxybutyrate |
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Steps of cholesterol metabolism |
Acetyl-CoA to Cholesterol
Rate limiting step: HMG-CoA (target of statins) |
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What happens during lipolysis by gut microbes |
Triglycerides hydrolyzed to fatty acids and glycerol
Glycerol fermented, not FA |
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Why are FA not fermented by gut microbes |
Not thermodynamically favorable due to high H2 in gut |
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What happens during biohydrogenation by gut microbes |
Unsaturated fatty acids to saturated (eg 18:3 to 18:0) |
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What are the most common fatty acids that are biohydrogenated |
alpha-linoleic (18:3)
linolenic (18:2)
oleic (18:1) |
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What are the most common lipid abnormalities |
1. Ketosis
2. Fatty Liver
3. Free Fatty Acid and toxicity to gut microbes
4. CLA and milk fat depression |
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What is ketosis |
accumulation of ketones caused by low blood glucose |
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What is fatty liver |
caused by high fat, CHO or cholesterol diet |
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Which CLA causes milk fat depression in ruminants |
Trans-10, cis-12 CLA |
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Ruminant products are ______ in saturated FA because of _________ in the rumen |
high;biohydrogenation |
