Monday, October 22, 2012

Multiple Choice Questions- Carbohydrate metabolism-Unsolved

Q.1 – Which of the following substrates derived from adipose tissues contributes to net Gluconeogenesis in mammalian liver?

a) Alanine

b) Glutamate

c) Glycerol

d) Pyruvate                                                                                                            

 Q.2 – Which of the following statements is incorrect?

 a) Aerobically, oxidative decarboxylation of pyruvate forms acetate that enters the citric acid cycle.

b) In anaerobic muscle, pyruvate is converted to lactate.

c) Reduction of pyruvate to lactate generates a coenzyme essential for Glycolysis.

d) Under anaerobic conditions pyruvate does not form because Glycolysis does not occur

Q.3- The steps of Glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following except:

 a) ATP synthesis.

b) Catalysis by phosphoglycerate kinase.

c) Oxidation of NADH to NAD+.

d) The formation of 1, 3- bisphosphoglycerate.                                                  

Q.4 – The oxidation of 3 mol of glucose by the pentose phosphate pathway may result in the production of:

 a) 2 mol of pentose, 4 mol of NADPH, and 8mol of CO2.

b) 3 mol of pentose, 4 mol of NADPH, and 3mol of CO2.

c) 3 mol of pentose, 6 mol of NADPH, and 3mol of CO2.

d) 4 mol of pentose, 3 mol of NADPH, and 3mol of CO2.                                  

Q.5 – How many ATP molecules can be derived from each molecule of acetyl CoA that enters the Krebs’ Cycle?

 a) 6

b) 12

c) 18

d) 38                                                                                                                                      

 Q.6 – All of the following vitamins except one participate in the TCA cycle-

 a) Pantothenic acid

b) Lipoic acid

c) Folic acid

d) Riboflavin                                                                                                                    

 Q.7 – Why Phosphofructokinase rather than hexokinase is the pace maker of Glycolysis?

 a) Glucose 6-phosphate is not solely a glycolytic intermediate

b) Hexokinase has low km for glucose

c) Hexokinase is inhibited by feed back inhibition

d) None of the above                                                                                                    

 Q.8 - All are correct about pyruvate dehydrogenase complex except one-

a) The formation of acetyl CoA from pyruvate is an irreversible step

b) Pyruvate dehydrogenase is switched off when Acetyl co A is in excess

c) Phosphorylation switches off the activity of the complex.

d) Pyruvate as well as ADP (a signal of low energy charge) inhibits the complex.

Q.9-Cellular isozymes of pyruvate kinase are allosterically inhibited by:

 a) High concentrations of AMP.

b) High concentrations of ATP.

c) High concentrations of Fr1,6 bisphosphate.

d) Low concentrations of acetyl-CoA.                                                                  

 Q.10 – Which of the followings is not an intermediate of the citric acid cycle?

 a) Acetoacetate


c)  Oxalo succinate

d) Succinyl-CoA                                                                                                              

 Q.11 - In an anaerobic system that is metabolizing glucose as a substrate, which of the following compounds would you expect to increase in concentration following the addition of fluoride?

 a) 2-phosphoglycerate

b) Glucose

c) Phosphoenolpyruvate

d) Pyruvate                                                                                                                          

 Q.12 – Which of the following is a coenzyme  in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

 a) ATP

b) Cu2+

c) Heme

d) NAD+                                                                                                                            

 Q.13 - An enzyme used in both glycolysis and gluconeogenesis is:

a) 3-phosphoglycerate kinase.

b)Glucose 6-phosphatase.

C) Hexokinase.


 Q.14 – Which of the following statements about the pentose phosphate pathway is incorrect?

 a) It generates 36 mol of ATP per mole of glucose consumed.

b) It generates 6 moles of CO2for each mole of glucose consumed

c) It is a reductive pathway; it consumes NADH.

d) It provides precursors for the synthesis of nucleotides                                

 Q.15 – Which of the following enzymes catalyzes a reaction that involves a decarboxylation reaction?

 a)Pyruvate dehydrogenase

b) Isocitrate dehydrogenase

c) α-keto glutarate dehydrogenase

d) all of the above                                                                                                            

 Q.16 -Anaplerotic reactions are those that result in replenishing intermediates in the TCA cycle. Which of the following enzymes catalyzes an Anaplerotic reaction?

a)   Malate dehydrogenase
b) Pyruvate carboxylase
c) Pyruvate kinase
d) Citrate synthase                                                                                                      

Q.17- Which statement BEST describes the fate of Propionyl-CoA in mammalian systems?

 a) Propionyl-CoA is metabolized via are action sequence that involves vitamin B12 and biotin.

b) Propionyl-CoA is converted to acetyl CoA.

c) Propionyl-CoA and acetyl CoA condense to form a 5 carbon precursor of a TCA cycle intermediate.

d) Propionyl-CoA is oxidized to Malonate and CoA                                          

Q.18 – It is very important to feed the baby very soon after birth, because during the first few hours after birth the enzyme Phosphoenolpyruvate carboxykinase is present in very low amounts, and this fact compromises:

a) Gluconeogenesis

b) Glucose phosphorylation

c) Glycogenesis

d) Glycogenolysis                                                                                                              

 Q.19 – The citric acid cycle is inhibited by which of the following?

 a) Fluoroacetate

b) Aerobic conditions

c) Malic acid

d) Fluorouracil                                                                                                                

 Q.20 – Which of the following enzymes is associated with Glycogen synthesis?

 a) Amylo- (1, 4->1,6) – transglycosylase

b) Phosphorylase

c) Amylo-1,6-glucosidase

d) Glucose-6- phosphatase                                                                                        

 Q.21 – A medical student developed hemolytic anemia after taking the oxidizing Antimalarial drug primaquine. This severe reaction is most likely due to

 a) Glucose-6- phosphate dehydrogenase deficiency

b) Concomitant Scurvy

c) Diabetes

d) Glycogen phosphorylase deficiency                                                                  

 Q.1-Which of the following enzymes is Thiamine dependent and essential for glucose oxidation in the brain?

a) Pyruvate dehydrogenase complex                

b) Acetyl co A carboxylase

c) Transaldolase                          

d) Succinyl-co A Thiokinase                                        

Q.2- The reaction catalyzed by phosphofructo kinase is -

 a) Inhibited by Fructose 2,6 bisphosphate                  

b) Activated by high concentration of ATP

c) A regulatory step of glycolysis  

d) All of the above                                                    

Q.3- Pyruvate carboxylase requires ————— as a coenzyme.

a) FMN                              

b) Biotin

c) NAD+

d) TPP                                                                      

Q.4- In erythrocytes the most abundantly found Phospho ester is-

 a) Glucose-6 phosphate                

b) Fructose 1, 6 bisphosphate

c) Fructose-6- phosphate

d) 2, 3 bisphosphoglycerate                                      

Q.5- Formation of Galactose-1-P from Galactose is catalyzed by-

a) Hexokinase                            

b) Aldolase    

c) Galactokinase                          

d) Galactose-1-P Uridyl transferase                              

Q.6- All the following enzymes except one require NADP+ as a coenzyme-

 a) Glucose- 6-phosphate dehydrogenase          

b) Cytosolic Isocitrate dehydrogenase

c) Malic enzyme      

d) Glucose-6-phophatase                                              

Q.7- Which of the following product of Triglyceride breakdown and subsequent beta oxidation would undergo gluconeogenesis-

a) Propionyl Co A                        

b) Acetyl CoA

c) Aceto acetate                          

d) Beta hydroxy butyrate                                                

Q.8 – Which of the following reactions generates ATP?

 a) Glucose to Glucose -6-phosphate        

b) Pyruvate to Lactate

c) Phosphoenol pyruvate to Pyruvate      

d) Glucose- 6 phosphate to fructose-6 phosphate            

Q.9- Glucose enters muscle cells mostly by:

 a) Simple diffusion

b) Facilitated diffusion using a specific glucose transporter

c) Co-transport with sodium

d) Co-transport with amino acids                                    

Q.10- Which one of the following compounds is common to both the oxidative phase and the non- oxidative phase of the pentose phosphate pathway?

 a) Xylulose-5- phosphate                        

b) Glucose-6-phosphate

c) Ribulose-5-phosphate                        

d) Glyceraldehyde-3- phosphate                                      

Q.11- Mc Ardle’s syndrome causes muscle cramps and muscle fatigue with increased muscle glycogen. Which of the following enzyme is deficient?

 a) Hepatic hexokinase                            

b) Muscle Phosphorylase

c) Muscle Debranching enzyme              

d) Muscle Hexokinase                                                        

Q.12- During starvation, the major source of blood glucose is-

 a) Hepatic Glycogenolysis                      

b) Gluconeogenesis

c)  Muscle Glycogenolysis                      

d) Dietary glucose from intestine                                        

Q.13- Hexokinase has a considerably lower km for-

 a) Glucose                                  

b) Fructose

c) Galactose

d) Mannose                                                                        

Q.14- In the fasting state there is considerable release of———–from the muscles.

 a) Glycine                                    

b) Alanine      

c) Valine

d) Glutamic acid                                                                

Q.15- A galactosemic child will manifest all except-

 a) Hepatomegaly                          

b) Splenomegaly

c) Cataract

d) Mental retardation                                                          

Q.16- – Which one of the following reactions is unique to gluconeogenesis-?

a) Lactate<———–>Pyruvate

b) Oxaloacetate—->Phosphoenol pyruvate

c) Glucose-6-phosphate—– >Glucose

d) Phosphoenol pyruvate–>Pyruvate                                  

Q.17- The main stores of glycogen are found in—

 a) Adipose tissues    

b) Skeletal muscles            

c) Brain                            

d) Erythrocytes                                                                  

Q.18- Succinyl co A is cleaved by-

 a) Succinate dehydrogenase          

b) Succinate Thiokinase

c) Succinate lyase                        

d) Succinate Thioesterase                                                  

Q.19- Arsenate binds to-

 a)  Free amino end of enzyme                

b) SH linkages

c) Free carboxyl end

d) Any of the above                                                              

Q.20- All are intermediates of glycolysis except-

a) Glucose-6 phosphate                

b) Fructose 1, 6 bisphosphate

c) Fructose-6- phosphate              

d) Glycerol – 3- phosphate                                                  

Q.21- The key regulatory enzyme of HMP pathway is-

 a) Glucose- 6-phosphate dehydrogenase

b) Transaldolase

c) Transketolase                          

d) Glucose-6-phophatase                                                      

Q.22- The net production of ATP in glycolysis during anaerobic condition is:

 a) 2 from glucose and 3 from glycogen

b) 2 from glucose and 4 from glycogen

c) 3 from glucose and 4 from glycogen

d) 3 from glucose and 2 from glycogen                                

Q.23- Which of the followings does not generate free glucose during the enzymatic breakdown of glycogen in skeletal muscles?

a) Phosphorylase                        

b) α-1-6-amyloglucosidase  

c) Debranching enzyme      

d) glucose-6-phosphatase                                                        

Q.24- Which of the followings promotes glucose and amino acid uptake by muscle?

a) Adrenaline                              

b) Insulin

c) Glucagon                                

d) Cortisol                                                                                  

Q.25- In a tissue that metabolizes glucose via the pentose phosphate pathway, C-1 of glucose would be expected to end up principally in:

a) Carbon dioxide                                  

b) Glycogen

c) Phosphoglycerate                              

d) Pyruvate                                                              

------------------------------------------ Best Wishes: Dr.Ehab Aboueladab, Tel:01007834123, ------------------------------------------
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