Question

LEO VIEW 6 Problem 3. Excess alcohol consumption can result in fatty liver disease. Liver cells synthesize triacylglycerides from fatty acids formed by fatty acid synthesis. Excess triacylglycerides can accumulate in the liver compromising normal liver function. Study the regulation of fatty acid metabolism shown in Fig. 12.22 (Mckee). A. Explain how palmitoyl-CoA is related to fatty acyl CoASH esters (acyl-CoA) B. Explain how increasing the rate of triglyceride formation changes the concentration of acyl-CoA in the cytosol. C. Explain how the rate of triglyceride formation stimulates the rate of fatty acid synthesis based on the concentration of palmitoyl-CoA in the cytosol D. Explain how stimulation of the rate of fatty acid synthesis changes the rate of fatty acid oxidation based on allosteric regulation of the rate-limiting step of beta-oxidation. I of 2 524 words 00 re

Answer 1

A) Palmitoyl-CoA yields 8 acetyl-CoA molecules and 14 pairs of hydrogen atoms, by seven cycles through the β-oxidation process. Acetyl-CoA is oxidized in the TCA cycle,and then used for the synthesis of fatty acidacid particularly cholesterol, or used for the formation of ketone bodies in the liver.The β-Oxidation of an acyl-CoA with uneven number of carbon atoms yields a propionyl-CoA during the acetyl-CoA acyltransferase reaction of the last cycle.

Two high-energy bonds are consumed for the activation of a fatty acid molecule. One mole of fatty acyl-CoA that cycles through reactions produces 1 mol of FADH2, 1 mol of NADH, and 1 mol of acetyl-CoA .

B ) The rate of fatty acid oxidation changes in response to the nutritional and hormonal state of an organism. The rate of fatty acid oxidation is high during fasting but low after the consumption of meall. The cause for this change is the higher concentration of unesterified fatty acids in the circulation of the fasting organism compared to the concentration in the fed one. An increased concentration of free fatty acids results in higher rates of cellular uptake and oxidation of fatty acids.After feeding, when carbohydrates are converted to triacylglycerols, thus increasing rate of fatty acid synthesis since acetyl-CoA carboxylase is active. This enzyme catalyzes the carboxylation of acetyl-CoA to malonyl-CoA, the first committed intermediate in fatty acid synthesis. Malonyl-CoA binds to and effectively inhibits CPT that initiates the uptake of fatty acids by mitochondria. Thus, when fatty acids are synthesized rapidly, the cytosolic concentration of malonyl-CoA becomes high and the mitochondrial uptake and oxidation of fatty acids are inhibited.

C) Palmitoyl-CoA yields 8 acetyl-CoA molecules and 14 pairs of hydrogen atoms, by seven cycles through the β-oxidation system. Thus, if the concentration of Palmitoyl-CoA increases, the rate of the formation of triglycerides increases .

D) Fatty acids are broken down to acetyl-CoA by beta oxidation inside the mitochondria, while fatty acids are synthesized from acetyl-CoA in the cytosol. The rate-limiting step in fatty acid synthesis is the formation of malonyl-CoA from acetyl-CoA by the enzyme acetyl-CoA carboxylase. So thus, when fatty acid concentrations increases, malonyl CoA increases, increasing mitochondrial uptake and inhibiting the fatty acid oxidation .