USMLE biochemistry- Exam Questions and Correct Answers Latest Version () Graded A+

USMLE biochemistry- Exam Questions and Correct Answers Latest Version () Graded A+ Fatty acid oxidation, occurs in the mitochondria or cytsol? - Answers mitochondria (break down fatty acids) AcetylCoA production, cytosol or mito? - Answers mitochondria TCA cycle, mitochondria or cytosol? - Answers mitochondira Fatty acid synthesis, mitochondria or cytosol? - Answers cytosol HMP shunt, located in mitochondria or cytosol? - Answers cytosol (next to PM) steroid synthesis, mitochondria or cytoplasm? - Answers cytosol What 3 metabolic processes occur in both the cytoplasm and mitochondria? - Answers Heme synthesis Urea cycle Gluconeogenesis (HUG) what co factor does carboylase use? - Answers biotin (buy-a-tin of CO2) Phosphofructokinase-1 is the RLM for? - Answers Glycolysis what are the+allosteric regulators of PFK-1 - Answers 1. AMP+, fructose-2,6-bisphosphate what are the - allosteric regulators of PFK-1? - Answers ATP, CItrate Fructose-1,6 Bisphosphatase is the RLM for what process? - Answers Gluconeogenesis What are the + allosteric regulators of GNG? - Answers 1. ATP, AcetylCoA What are the -negative allosteric regulators of GNG? - Answers AMP, F-2,6-BP Isocitrate Dehydrogenase is the RLM enzyme for what process? - Answers TCA cycle What are the allosteric regulators of isocitrate dehydrogenase? (give +/-) - Answers +: ADP -: ATP, NADH What disease has excess NADH leading to inhibition of TCA cycle via isocitrate dehydrogenase? - Answers Alcoholism. Excess EtOH leads to increased NADH. Glycogen synthetase is the RLM for what process? - Answers Glycogen synthesis What are the allosteric regulators of glycogen synthetase? - Answers +:Glucose-6-Phosphate, insulin, cortisol -:epinephrine, glucagon Glycogen Phosphorylase is the RLM for what process? - Answers Glycogenolysis What are the allosteric regulators of glycogen phosphorylase? - Answers +: epinephrine, glucagon, AMP -:Glucose-6-Phosphate, insulin, ATP What is the RLM of HMP shunt? - Answers Glucose-6-phosphate dehydrogenase What is the RLM of de novo pyrimidine synthesis? - Answers Carbamoyl phosphate synthetase II What is the RLM of de novo purine synthesis? - Answers PPRP What is the RLM of the urea cycle? - Answers Carbamoyl phosphate I Acetyl CO-A carboxylase is the RLM of what reaction? - Answers Fatty acid synthesis Carnitine acyltransferase I is the RLM for what process? - Answers Fatty acid degredation What is the RLM of ketogenesis? - Answers HMG CO synthase What is the RLM of cholesterol synthesis - Answers HMG CO reductase what are the allosteric regulators of HMG COaReductase? - Answers +: insulin, thyroxine -:glucagon, cholesterol Aerobic metabolism produces how many net ATP via the malate aspartate shuttle? - Answers 32 How many ATP produced via the glycerol 3-Phosphate shuttle? - Answers 30 How many ATP does anaerobic glycolysis produce? - Answers 2 arensic causes ATP production become what? - Answers 0 NAD+ is used in anabolic processes T/F? - Answers False, NAD+ is used in catabolic processes (think glycolysis/TCA) NADPH is used in anabolic processes T/F? - Answers True! steroid or fatty acid synthesis, provides reducing equivalents. Name the 4processes NADPH is involved in - Answers 1. Anabolic processes 2. respiratory burst 3. cytochrome p450 system 4. glutathione reductease what the action of glucokinase/hexokinase? - Answers to phosphoyrlate glucoseglucose-6-phosphate which can now enter glycolysis OR enter the first step of glycogen synthesis Where is hexokinase found? - Answers most tissues (excludes liver, pancreas beta cells) Where is glucokinase found? - Answers Liver, Beta cells of pancreas. Describe glucokinase compared to hexokinse: KM, Vmax, Affinity, capacity, insulin responsive, feedback by G6p - Answers Glucokinase: Higher KM/lower affinity High Vmax/high capacity Yes, induced by insulin No, not inhibited by G6P T/F glucokinase is associated with MODY (maternal-onset diabetes of the young) - Answers True what two enzymes of glycolysis produce ATP - Answers 1. phosphoglycerate kinase (3PG1,3BPG) 2. pyruvate kinase (PEPpyruvate) F2,6BP: in the fed state what happen to F2,6BP? - Answers Inuslin decreases CAMP, decreases PKA. This decreases FBPase2 and increases Phosphofructokinase-2. PFK-2 increases F2,6BP and this allosterically increaes Phosphofructokinase-1 (the RL step in glycolysis) F2,6BP: in the fasting state what happen to F2,6BP? - Answers Glucagon increases cAMP, increases PKA. This increase Fructose bisphosphatase-2 and decreases F,26BP. This shunts fructose-6-Phosphate toward gluconeogenesis. Summary: what happens to F2,6 BP in the fed and fasting state (state PKA and cAMP levels) - Answers Fed state: cAMP and PKA decreases, leads to increase F2,6BP levels and glycolysis is enhanced.