Consider a preparation that contains all the enzymes and cofactors necessary for fatty acid biosynthesis from acetyl-CoA and malonyl-CoA. If [2-H] acetyl-CoA labeled with deuterium, the heavy isotope of hydrogen and excess of unlabeled malonyl-CoA are added as substrates, where will you find these labeled deuterium atoms in a molecule of palmitate synthesized? Explain. K. Describe the steps involved in the synthesis of palmitic acid starting from acetyl-CoA and malonyl-CoA.

3. (a) Wakil's pioneering studies on fatty acid synthesis included the crucial observation that bicarbonate is required for the synthesis of palmitoyl-CoA. He was surprised to find that very low levels of bicarbonate could sustain palmitate synthesis; that is, there was no correlation between the amount of bicarbonate required and the amount of palmitate produced. Later he also observed that 14C-labeled bicarbonate is not incorporated into palmitate. Explain these observation (b) The condensation reaction catalyzed by B-ketoacyl-ACP synthase generates a 4-carbon unit by combining a 2-carbon unit with a 3-carbon unit and loss of CO2. Write with structural formulas how this occurs. What is the thermodynamic advantage of this way of generating the 4-carbon unit over combining two 2-carbon units as occurs fatty acid oxidation or ketone body reactions" (c) Decide where labeled carbon atoms will be found in palmitate if (i) (3-1“C)malonyl-SCOA or (ii) (2- 14C)malonyl-SCOA are used.

The mechanism of chymotrypsin can be viewed as a two-step process, acylation of the enzyme active site followed by a deacylation reaction. What accounts for the observed "burst" in rapid kinetic studies of the hydrolysis of N-acetyl-L-phenylalanine p-nitrophenyl ester by chymotrypsin? The rate of hydrolysis of the acyl-enzyme intermediate is faster than the rate of forming the acyl-enzyme intermediate. The rates of the acylation and deacylation reactions are equal. The rate of the acylation reaction is slower than the rate of the deacylation reaction. The rate of the acylation reaction is faster than the rate of the deacylation reaction.

Draw the products that would be produced from phospholipase C cleavage of a glycerophospholipid with a phosphoserine head group, an alpha linoleic acid attached to C2 of glycerol and a linoleic acid attached to C, of glycerol. Draw these products at pH=1. Be sure to number the fatty acid carbons in your products.