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STUDY SHEET MIDTERM 2 (BIS 103 FALL 2007) - Roy H. Doi Fatty Acids (a.k.a. acyl groups) Contain carboxylic acid head group and long hydrocarbon tail. 3 fatty acids and a glycerol molecule make up a triacylglycerol/triglyceride (TAG - storage form of fat) 3 main physiological roles: 1) Building blocks for phospholipids (amphipathic molecules that make up cell membranes) and glycolipids. 2) Precursor for hormones and intracellular messengers. 3) Energy storage (TAG). What are the advantages and disadvantages having fat as the primary energy reserve? Usually have an even number of carbons. Most common are 16C and 18C. Saturated vs. Unsaturated (at least one double bond in the hydrocarbon chain). Less unsaturated bonds and/or longer carbon chain = higher melting point. Digestion and absorption of fats: Bile salts, synthesized from cholesterol, are released from gall bladder and emulsify fats into mixed micelles in the small intestine. Lipase is the enzyme that breaks TAG into fatty acids and glycerol, which is taken up by intestinal mucosal cells. FA’s and glycerol are reconverted to TAG and incorporated into chylomicrons, which are carried to muscles, adipose tissue, etc. Lipoprotein lipase hydrolyzes TAG in chylomicrons to FA’s and glycerol, and taken up by the tissues. FA’s and glycerol can be reconverted to TAG for storage or used for energy needs. Know the cascade effect which initiates TAG breakdown to FA’s and glycerol. 3 fates of glycerol: 1) backbone for TAG. 2) converted to DHAP pyruvate. 3) converted to DHAP gluconeogenesis. Know 3 step system to take FA’s from cytosol to mitochondrial matrix. Energy cost for this process: 2 ATP’s (ATP AMP + PPi). (p. 32 in booklet) Beta-oxidation (Fatty Acid Degradation ) Function: supply acetyl-CoA to fulfill energy needs of the body. Location: mitochondrial matrix Four step process: 1) oxidation (acyl-CoA DH). 2) hydration (enoyl-CoA hydratase). 3) oxidation (hydroxyacyl-CoA DH). 4) transfer (thiolase). One cycle of β -oxidation: acyl-CoA + FAD + H 2 O + NAD + CoASH acyl-CoA(-2C) + FADH 2 + NADH + H + + Acetyl-CoA. (p. 33 in booklet) Complete oxidation of palmityl-CoA (C16) uses 7 cycles; stearyl-CoA (C18) uses 8 cycles; etc. Be able to calculate the number of acetyl-CoA, NADH, FADH 2 , ATP produced, and H 2 O used. Also be able to calculate ATP and H 2 O produced from acetyl-CoA, NADH, and FADH 2 (made during FA oxidation). (Note: H 2 O is produced during oxidation of NADH and FADH 2 ) Remember that 2 ATP’s are used initially to activate FA with CoASH to form acyl-CoA. Understand oxidation of saturated FA vs. unsaturated FA (one less FADH
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