BioChemistry Homework 7 Questions & Answers

The function of the Krebs/citric acid/tricarboxylic acid (TCA) cycle is: -to harvest high-energy electrons in the form of ATP/GTP, NADH, and FADH2. -to generate anapleurotic metabolites for other cellular pathways. -to replenish NAD+ for glycolysis. -to create acetyl-CoA from fatty acids for gluconeogenesis. - ANSWERSto harvest high-energy electrons in the form of ATP/GTP, NADH, and FADH2. to generate anapleurotic metabolites for other cellular pathways. Which of the following can serve as precursors for the citric acid cycle? Amino acids Nucleotide bases Porphyrin Oxaloacetate All of the above. - ANSWERSall Although we study the citric acid cycle as the final stage oxidation of carbon from glucose, an in-depth look at the cycle shows intermediates entering and leaving the cycle from a number of metabolic pathways. With all of these demands on the cycle, how does it maintain a minimal level of oxaloacetate (OAA) to allow the cycle to function? -OAA can be formed by the condensation of two moles of acetyl CoA and occurs when the energy charge of the cell is high. -The rate of the cycle is increased when the cell has high levels of NADH. -Isocitrate dehydrogenase is allosterically inhibited by ADP, which signifies the need for more energy. -OAA is formed directly via the deamination of glutamate. -OAA is synthesized via pyruvate carboxylase in an anapleurotic reaction that occurs when acetyl CoA is present, such as from fatty acid breakdown - ANSWERSOAA is synthesized via pyruvate carboxylase in an anapleurotic reaction that occurs when acetyl CoA is present, such as from fatty acid breakdown