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------------------------------------------ Best Wishes: Dr.Ehab Aboueladab, Tel:01007834123 Email:ehab10f@gmail.com,ehababoueladab@yahoo.com ------------------------------------------
Monday, October 22, 2012
نصائـح طبيـة للحـاج
------------------------------------------ Best Wishes: Dr.Ehab Aboueladab, Tel:01007834123 Email:ehab10f@gmail.com,ehababoueladab@yahoo.com ------------------------------------------
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
b)Citrate
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.
d)Phosphofructokinase-1.
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 Email:ehab10f@gmail.com,ehababoueladab@yahoo.com ------------------------------------------
The answer
1) The answer is –b) Beta hydroxy Butyrate, a ketone body. Ketone bodies serve as alternative fuel for brain during prolonged fasting or starvation. Fatty acids due to long hydrophobic chain can not cross blood brain barrier. Glycerol is a substrate of gluconeogenesis. In fact during prolonged fasting this is the only substrate left to provide glucose through pathway of gluconeogenesis. It can be oxidized through glycolysis after phosphorylation. Beta carotene is a provitamin; it is not a source of energy.
2) The answer is –a) Fatty acid break down provides Acetyl co A that serves as a precursor for ketone bodies. In Diabetes Mellitus glucose utilization is impaired due to absolute or relative insulin deficiency. Fatty acid breakdown occurs to provide energy and the resultant excessive Acetyl co A enters the pathway of ketogenesis. Protein breakdown provides amino acids, 6 amino acids are ketogenic, while 14 are glucogenic. Hence protein breakdown contributes only a little towards formation of Acetyl co A. The major contribution is through fatty acid breakdown. Glycogenolysis and Gluconeogenesis produce glucose only.
3) The answer is –a) Galactosemia. The clinical manifestations are typical of classical Galactosemia. Bilateral cataract rules out the possibility of Von Gierke’s disease and hereditary fructose intolerance, although other symptoms are there in both these diseases. In juvenile diabetes mellitus, jaundice and hepatomegaly are not observed.
4) The answer is-d)- Lactate, the end product of glycolysis in erythrocytes and during intense exercise in skeletal muscles ,is mobilized through Cori cycle to liver to provide glucose by the process of gluconeogenesis. (Erythrocytes lack mitochondria so the end product of glycolysis is always lactate. The mode of glycolysis during intense exercise is anaerobic; hence lactate is formed as a result of glycolysis.
Alanine is transported to liver through Glucose Alanine cycle. Glycerol is also similarly transported but not from the erythrocytes or skeletal muscles, rather from the adipose tissues. Glycerol is a waste product in adipose tissues since without phosphorylation it can not be utilized and the phosphorylating enzyme glycerol kinase is absent in adipose tissues.
5) The answer is-b) Branching enzyme. During the process of glycogen synthesis, branching enzyme creates branch points and further elongation is carried out by Glycogen synthase . In its deficiency stored glycogen is abnormal in chemistry, in the form of long polysaccharide chains with few branch points, resembling the structure of Amylopectin, thus this defect is also called Amylopectinosis. Alpha Amylase is an enzyme for digestion of starch and glycogen. Debranching enzyme deficiency results in the accumulation of abnormal glycogen, There is inability to remove the branch points, the resultant structure resembles Limit dextrin , thus it is also called Limit dextrinosis
6) The answer is-d) The hydrolysis of starch is catalyzed by salivary and pancreatic amylases, which catalyze random hydrolysis of alpha (1- 4) glycoside bonds, yielding dextrins, and further hydrolysis yields a mixture of glucose, maltose, isomaltose (from the branch points in amylopectin) and maltotriose.
7) The answer is- c) Palmitate, a fatty acid with 16 carbon atoms, is not a substrate for gluconeogenesis. Even chain fatty acids, predominantly present in our body, yield Acetyl co A upon oxidation, which can not contribute towards gluconeogenesis. The Pyruvate to Acetyl co A conversion is irreversible and moreover both of the carbon atoms of Acetyl co A are lost in the TCA cycle in the form of CO2.Oddchain fatty acid do act as substrates of gluconeogenesis, since propionyl co A the product of their oxidation can enter TCA cycle through formation of Succinyl co A, hence can contribute towards Glucose production.
8) The answer is-d) Hypoglycemic coma occurs as a result of insulin over dosage in Type 1diabetes Mellitus. It is not observed in Type 2 diabetes. Weight gain can occur in both types, it is the result of treatment with insulin or certain hypoglycemic drugs.
9) The answer is- a) Hexokinase is a non specific enzyme, it can phosphorylate fructose as well as other sugars but it has high km(low affinity) for fructose. Glucose is the true substrate for this enzyme.Fructose-6-phosphatethe end product of Hexokinase reaction can enter glycolytic pathway to be utilized further, so it does not accumulate to produce the toxic effects. Liver Aldolase (Aldolase B) cleaves Fructose-1-P only, the product of fructokinase catalyzed reaction. Aldolase A, present in all the cells of the body cleaves Fructose 1,6 bisphosphate, the product of PFK-1 catalyzed reaction of glycolysis.
10) The answer is- b) Free glucose is released by the action of α-1-6-amyloglucosidaseenzyme, a component of debranching enzyme. Debranching enzyme has two components. α-[1 4] -α-[1 4] Glucan transferase and α-1-6-amyloglucosidase.Glucan transferase shifts the trisaccharide on a branch bound by α-[1- 4] linkage to the straight chain and joins by α-[1 4] linkage. The exposed branch point is hydrolyzed by α-1-6-amyloglucosidase enzyme. Both components are present on the same polypeptide chain. Glucose-6- phosphatase does produce free glucose but it is absent in skeletal muscles.
------------------------------------------ Best Wishes: Dr.Ehab Aboueladab, Tel:01007834123 Email:ehab10f@gmail.com,ehababoueladab@yahoo.com ------------------------------------------
Carbohydrate metabolism
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 ( a )
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 ( c )
Q.3- Pyruvate carboxylase requires ————— as a coenzyme.
a) FMN
b) Biotin
c) NAD+
d) TPP ( b )
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 ( d )
Q.5- Formation of Galactose-1-P from Galactose is catalyzed by-
a) Hexokinase
b) Aldolase
c) Galactokinase
d) Galactose-1-P Uridyl transferase ( c )
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 ( d )
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 ( a )
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 ( c )
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 ( b )
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 ( a )
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 ( b )
Q.12- During starvation, the major source of blood glucose is-
a) Hepatic Glycogenolysis
b) Gluconeogenesis
c) Muscle Glycogenolysis
d) Dietary glucose from intestine ( b )
Q.13- Hexokinase has a considerably lower km for-
a) Glucose
b) Fructose
c) Galactose
d) Mannose ( a )
Q.14- In the fasting state there is considerable release of———–from the muscles.
a) Glycine
b) Alanine
c) Valine
d) Glutamic acid ( b )
Q.15- A galactosemic child will manifest all except-
a) Hepatomegaly
b) Splenomegaly
c) Cataract
d) Mental retardation ( b )
Q16- – 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 ( b )
Q.17- The main stores of glycogen are found in—
a) Adipose tissues
b) Skeletal muscles
c) Brain
d) Erythrocytes ( b )
Q.18- Succinyl co A is cleaved by-
a) Succinate dehydrogenase
b) Succinate Thiokinase
c) Succinate lyase
d) Succinate Thioesterase ( b )
Q.19- Arsenate binds to-
a) Free amino end of enzyme
b) SH linkages
c) Free carboxyl end
d) Any of the above ( b )
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 ( d )
Q.21- The key regulatory enzyme of HMP pathway is-
a) Glucose- 6-phosphate dehydrogenase
b) Transaldolase
c) Transketolase
d) Glucose-6-phophatase ( a )
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 ( a )
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 ( a )
Q.24- Which of the followings promotes glucose and amino acid uptake by muscle?
a) Adrenaline
b) Insulin
c) Glucagon
d) Cortisol ( b )
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 ( a )
------------------------------------------ Best Wishes: Dr.Ehab Aboueladab, Tel:01007834123 Email:ehab10f@gmail.com,ehababoueladab@yahoo.com ------------------------------------------
Multiple Choice Questions- Carbohydrate metabolism
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 ( c )
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.
( d )
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. ( c )
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. ( c )
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 ( b )
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 ( c )
Q.7 – Why Phosphofructokinase rather than hexokinase is the pacemaker 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 ( a )
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. ( d )
Q.9-Cellular isozymes of pyruvate kinase are allosterically inhibited by:
a) High concentrations of AMP.
b) High concentrations of ATP.
c) High concentrations ofFr1,6 bisphosphate.
d) Low concentrations of acetyl-CoA. ( b )
Q.10 – Which of the followings is not an intermediate of the citric acid cycle?
a) Acetoacetate
b) Citrate
c) Oxalosuccinate
d) Succinyl-CoA ( a )
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 ( a )
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+ ( d )
Q.13 - An enzyme used in both glycolysis and gluconeogenesis is:
a) 3-phosphoglycerate kinase.
b)Glucose 6-phosphatase.
C) Hexokinase.
d)Phosphofructokinase-1. ( a )
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 ( c )
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 ( d )
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 ( b )
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 ( a )
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 ( a )
Q.19 – The citric acid cycle is inhibited by which of the following?
a) Fluoroacetate
b) Aerobic conditions
c) Malic acid
d) Fluorouracil ( a )
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 ( a )
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 ( a )
Q.22- Which of the following explains why individuals with hyperlipidemia should minimize their intake of sucrose and high fructose syrup?
a) Fructose metabolism is faster than glucose
b) After initial modification fructose is cleaved by a specific Enolase
c) Fructose is ultimately converted to galactose
d) Fructose can be phosphorylated by hexokinase in adipose cells ( a )
Q.23-The major glycolytic product produced under normal circumstances by erythrocytes required for unloading of oxygen to the peripheral tissues is
a) 2,3bisphosphoglycerate
b) 1,3bisphosphoglycerate
d)Lactate ( a )
c) Pyruvate
Q.24 – Poorly perfused areas exposed to chronic hypoxia have decreased metabolic energy for tissue maintenance and repair an important reason for this is-
a) Increased hexokinase activity owing to increased oxidative phosphorylation
b) Decreased ATP production and increased glucose utilization due to an aerobic mode of glycolysis
c) Increased glucose utilization by HMP pathway on changing from anaerobic to aerobic glycolysis
d) Decreased respiratory quotient on changing from carbohydrates to fats as the major fuel ( b )
Q.25 – Asians and Native Americans may flush and feel ill after drinking a small amount of ethanol in alcoholic beverages. This reaction is due to genetic variation in an enzyme that metabolizes the liver metabolite of alcohol, which is-
a) Methanol
b) Acetone
c) Acetaldehyde
d) Glycerol ( c )
Q.26 – Which one of the following enzymes catalyzes the phosphorylation of the substrate with the use of inorganic phosphate-?
a) Hexokinase
b) Phospho fructokinase
c) Glyceraldehyde-3-phosphate dehydrogenase
d) Phospho glycerate kinase ( c )
------------------------------------------ Best Wishes: Dr.Ehab Aboueladab, Tel:01007834123 Email:ehab10f@gmail.com,ehababoueladab@yahoo.com ------------------------------------------
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