Transcript Theory21_30
BCHM2072/2972 2004 THEORY PAPER MCQs 21 - 30 21.Glucose uptake into tissues following a carbohydrate meal is facilitated by: F A. T B. F C. F D. F E. an increased number of GLUT-2 transporters on the muscle cell surface a loss of GLUT-4 transporters from the muscle Golgi apparatus insulin-stimulation of glucose uptake into the liver an increase in GLUT-1 expression in brain cells rapid trapping of glucose in muscle cells by glucokinase 22. Which of the following properties is NOT a feature of a typical rate limiting enzyme and/or flux generating step? Is A. The step is irreversible Is B. The concentration of the substrate is very much greater than the Km of the enzyme Is C. The enzyme operates under Vmax conditions Is D. The activity of the enzyme can be regulated by changes in gene expression NOE. The enzyme is regulated by the concentration of substrate alone 23. As a check on the scanning procedure enter an answer of A to question 23 on the answer sheet 24. Which statement regarding the conversion of glucose to glycogen in muscle is CORRECT? F A. F B. F C. T D. F E. Glycogenesis is stimulated by phosphorylation of glycogen synthase NADPH is required for the conversion of glucose 6-phosphate to glycogen Insulin directly stimulates phosphofructokinase to provide ATP for glycogenesis The consumption of ATP during glycogenesis results in an increased flux through glycolysis A new molecule of glycogenin is required each time a branch point is made in the growing glycogen chain 25. Which statement regarding the disposal of glucose by liver and muscle is INCORRECT? T A. T B. T C. F D. T E. Insulin is essential for glycogen synthesis in muscle, but not liver The concentration of glucose 6-phosphate can rise high enough in liver to stimulate glycogen synthase, but this does not happen in muscle A build up of glucose 6-phosphate inhibits further glucose trapping in muscle, but not liver In liver, but not muscle, glucose is only made into glucose 6-phosphate if it is going to be made into glycogen The intracellular [glucose] is always equal to blood [glucose] in liver cells, but not muscle cells 26. Which of the following changes DOES NOT occur during lipogenesis (the conversion of glucose to fatty acids)? Y A. Y B. N C. Y D. Y E. The polymerization of acetyl CoA carboxylase (ACC) increases The production of malonyl CoA increases The cleavage of citrate in the cytoplasm decreases The consumption of NADPH increases The consumption of ATP increases 27. If you added 14C malonyl CoA, labelled in the carboxylic acid carbon (see diagram below), to cells undergoing fatty acid synthesis to palmitate (C16) where would you expect to recover the label? -OO14C-CH2-CO-S-CoA malonyl CoA A. !!! B. C. D. E. On the odd numbered carbons of palmitate None of the carbon atoms in palmitate On the carboxyl carbon (carbon 1) of palmitate On the even numbered carbons of palmitate On the omega-carbon (carbon 16) of palmitate Use the following information to answer Questions 28-29 The following enzymes (A-E) are all involved in the synthesis of fatty acids from glucose: A. Glucose 6-phosphate dehydrogenase First step of PPP. NADPH production. Up when NADP low. B. ATP citrate lyase Splitting citrate in cytoplastm to give cytosolic acetyl CoA C. Acetyl CoA carboxylase Making malonyl CoA D. Pyruvate dehydrogenase Making acetyl CoA. Irreversible Glucose oxidation. E. Phosphofructokinase Rate limiting step of glycolysis 28. Which enzyme (A-E) is DIRECTLY regulated by the A availability of NADP+? D 29. Which enzyme (A-E) catalyses the step after which the products cannot be reconverted back into glucose? 30. During the synthesis of fatty acids from acetyl CoA, which type of reaction DOES NOT happen? N Y Y Y Y A. B. C. D. E. Hydration of a double bonded carbon Reduction of a ketone (C=O) to an alcohol (C-OH) Carboxylation Decarboxylation Reduction of a double bonded carbon (-CH=CH-) Carboxylate AcCoA to malonlyl CoA. Lose CO2 on condensation step. Start with –C=O, reduce to –CH-OH, dehydrate to –C=C-, reduce to –CH2-CH2-.