Problem 2
NADH to NADPH. What are the three reactions that allow the conversion of cytoplasmic NADH into NADPH? What enzymes are required? Show the sum of the three reactions.
Problem 3
A pledge to move forward. What is the committed step in fatty acid synthesis, and which enzyme catalyzes the step?
Problem 4
Like sugar \(n\) spice. Match each term (a-j) with its description ( \(1-10\) ). (a) ATP-citrate lyase ________ (b) Malic enzyme ______ (c) Malonyl CoA ________ (d) Acetyl CoA carboxylase 1 ___________ (e) Acyl carrier protein _________ (f) \(\beta\) -Ketoacyl synthase (g) Palmitate ________ (h) Eicosanoids ________ (i) Arachidonate ___________ (j) AMP-activated protein kinase ______ 1\. Helps to generate NADPH from NADH 2\. Inactivates acetyl CoA carboxylase 1 3\. Molecule on which fatty acids are synthesized 4\. A precursor of prostaglandins 5\. Activated acetyl CoA 6\. The end product of fatty acid synthase 7\. Fatty acids containing 20 carbon atoms 8\. Catalyzes the committed step in fatty acid synthesis 9\. Catalyzes the reaction of acetyl CoA and malonyl CoA 10\. Generates cytoplasmic acetyl CoA
Problem 7
7\. Proper organization. Arrange the following steps in fatty acid synthesis in their proper order. (a) Dehydration (b) Condensation (c) Release of a \(\mathrm{C}_{16}\) fatty acid (d) Reduction of a carbonyl (e) Formation of malonyl ACP
Problem 8
No access to assets. What would be the effect on fatty acid synthesis of a mutation in ATP-citrate lyase that reduces the enzyme's activity? Explain.
Problem 9
The truth and nothing but. Indicate whether each of the following statements is true or false. If false, explain. (a) Biotin is required for fatty acid synthase activity. (b) The condensation reaction in fatty acid synthesis is powered by the decarboxylation of malonyl CoA. (c) Fatty acid synthesis does not depend on ATP. (d) Palmitate is the end product of fatty acid synthesis. (e) All of the enzyme activities required for fatty acid synthesis in mammals are contained in a single polypeptide chain. (f) Fatty acid synthase in mammals is active as a monomer. (g) The fatty acid arachidonate is a precursor for signal molecules. (h) Acetyl CoA carboxylase 1 is inhibited by citrate. 10\. Odd fat out. Suggest how fatty acids with odd numbers of carbon atoms are synthesized. 11\. Alpha or omega? Only one acetyl CoA molecule is used directly in fatty acid synthesis. Identify the carbon atoms in palmitic acid that were donated by acetyl CoA.
Problem 11
Alpha or omega? Only one acetyl CoA molecule is used directly in fatty acid synthesis. Identify the carbon atoms in palmitic acid that were donated by acetyl CoA.
Problem 12
Now you see it, now you don't. Although \(\mathrm{HCO}_{3}^{-}\) is required for fatty acid synthesis, its carbon atom does not appear in the product. Explain.
Problem 13
The fizz in fatty acid synthesis. During the initial invitro studies on fatty acid synthesis, experiments were performed to determine which buffer would result in optimal activity. Bicarbonate buffer proved far superior to phosphate buffer. The researchers could not initially account for this result. From your perspective of many decades later, explain why the result is not surprising.
Problem 14
Tracing carbon atoms. Consider a cell extract that actively synthesizes palmitate. Suppose that a fatty acid synthase in this preparation forms one molecule of palmitate in about 5 minutes. A large amount of malonyl CoA labeled with \(^{14} \mathrm{C}\) in each carbon atom of its malonyl unit is suddenly added to this system, and fatty acid synthesis is stopped a minute later by altering the \(\mathrm{pH}\). The fatty acids are analyzed for radioactivity. Which carbon atom of the palmitate formed by this system is more radioactive-C-1 or C-14?
