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Unit 1: Lipids
Terms in this set (36)
what are some classes of lipids?
what are some characteristics of lipids?
-large hydrophobic surfaces
-not water soluble
-are an energy source
-found in membranes
was are some uses for lipids/fatty acids?
-free FA's are oxidized for energy
-stored in TAGs
-are structural components in phospholipids and glycolipids
what is the general structure of lipids and fatty acids?
-have a hydrophobic hydrocarbon chain
-have a hydrophilic carboxyl group (is ionized at pH 7)
*long-chain fatty acids are water insoluble (carbon chain has more than 12 C's)
what is the relationship between carbon chain length and aqueous solubility?
-the longer the carbon chain, the less soluble the carboxylic acid will be (i.e.: propanoic acid [3C's] is more soluble than heptanoic acid [7C's])
which are more common: cis or trans carbon chains?
cis (C's after the double bond face the same side) because it is harder for the carbon chains to stack on top of each other and so they remain more fluid than if the carbon chain double bonds were trans
what are the 4 FA classifications according to Krause?
1) VLCFA (very long chain FA) - +22 C's
2) LCFA (long chain FA) - 16-22 C's
3) MCFA (middle " " " ) - 8-14 C's
4) SCFA (short " " " ) - 4-6 C's
how are fatty acids classified according to bonds?
-saturated = 0 double bonds
-monounsaturated = 1 double bond
-polyunsaturated = +2 double bonds
what does 18:1(9) represent?
-18 = the # of C's in the chain
-1 = the # of double bonds in the chain
-(9) = where the double bond is located relative to the carboxylic acid terminal end of the chain
what is the difference between omega-3 and omega-6 FA's?
-the location of the first double bond relative to the omega terminal end of the FA
-omega-3 means the first double bond relative to the omega end is 3 C's away from the omega terminal end (omega-6 = the double bond is 6 C's away)
what are linoleic acid and alpha-linolenic acid?
-both are essential fatty acids
-linoleic acid is a precursor for arachidonic acid and is also a substrate for prostaglandin synthesis
-alpha-linolenic acid is a precursor for omega-3 FA's needed for growth and development (DHA and EPA)
how are double bonds spaced in polyunsaturated FA's?
the double bonds are space 3 C's apart
how does chain length impact melting point?
the longer the chain (the more C's) the higher the melting point (it increases)
how are most triacyglycerols (TAGs) stored?
what makes up TAG's?
-TAG = glycerol + 3 FA's
-are esters and are neutral (have no H to donate)
-are a form of energy storage
what is Coenzyme A?
-it is a thiol
-essential to help turn glycerol-P into triacylglycerol
what are phospholipids made up of?
choline head, followed by phosphate, glycerol (all 3 make up the hydrophilic head of the phospholipids), and finally fatty acid tails (make up the hydrophobic tails of phospholipids)
which compounds can pass freely through lipid bilayers?
what is cholesterol?
-is a major sterol in animals
-is found in cell membranes (helps stabilize it)
-has an alkyl side chain located at C17 and has a an OH group at position 3
-can be esterified
what are cholesteryl esters?
-are cholesterols that have been esterified (seen in plasma)
-is not found in cell membranes
-only occurs in low levels in the cell
what transports cholesterol and cholesteryl esters?
what is the relationship between alcohols and solubility?
the longer the carbon chain of the alcohol, the less soluble it is (6 C's = marginally soluble vs. 2 C's = soluble)
name the different classes of lipids
1) cholesteryl esters (CE)
2) phospholipids (PL)
3) triacylglycerol (TAG)
what breaks dietary lipids down?
-are emulsified by bile salts
-are degraded by pancreatic enzymes
what are the primary products of CE/PL/TAG degradation?
free fatty acids, 2-monoacylglycerol, and cholesterol
what happens to dietary lipids in the stomach, duodenum, pancreas, and intestine?
-stomach: milk fat is degraded; find lingual and gastric lipase's
-duodenum: emulsification; detergent properties of bile salts; peristalsis
-pancreas: pancreatic enzymes
-intestine: absorption (cholesterol, free FA's, monoacylglycerol); repackaging
what is peristalsis?
is a radially symmetrical contraction of muscles which propagates in a wave down the muscular tube
-in humans, peristalsis is found in the contraction of smooth muscles to propel contents through the digestive tract
what does emulsify mean?
how are TAGs degraded?
-in the stomach via lingual and gastric lipase
-breaks down SCFAs and MCFAs
-pancreatic lipase removes FAs at C1 and C3
-colipase forms a 1:1 dimer with lipase and anchors it to the lipid-aqueous interface
-produces monoacylgycerol and FAs
-Orlistat inhibits lipase, decreasing fat absorption
how are lipids absorbed at the jejunum?
-absorbs free FAs, 2-monoacylglycerol, and free cholesterol
-forms fixed micelles with bile salts and fat-soluble vitamins
-micelles can penetrate the unstirred water layer around the brush border membranes aiding the absorption of hydrophobic lipids
-FAs with short and medium sized chains do not need micelles
what makes up bile?
salts, phospholipids, free cholesterol
what are chylomicrons?
are particles of lipid droplets surrounded by a layer of phospholipids, free cholesterol, and a molecule of apolipoprotein B-48
what happens to the fatty acids after they are digested?
-SC and MC FA's are released (into serum albumin)
-lipids are sent to the ER of enterocytes for biosynthesis
-TAGs and CEs are produced
-TAGs and CEs are packaged into chylomicrons and are released into the lymphatic system (part of chyle)
what are the different types of lipoproteins?
-very low density lipoproteins (VLDL)
-low density lipoproteins (LDL)
-high density lipoproteins (HDL)
what are the functions of chylomicrons and VLDL's?
-chylomicrons: deliver dietary lipids from small intestines to peripheral tissues
-VLDLs: deliver lipids from the liver to peripheral tissues
what are the functions of LDLs and HDLs?
-LDL's: provide cholesterol to peripheral tissues
-HDL's: deliver cholesterol from peripheral tissues to the liver; also involved in apolipoprotein reservoirs, cholesterol uptake, and esterification of cholesterol
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