Monday, October 22, 2012

Multiple choice questions- Enzymes

Q.1- Glycogen phosphorylase, which mobilizes glycogen for energy, requires which of the followings as a cofactor?
a)Pyridoxal phosphate
b)Tetra hydro folate
c)Adenosyl Cobalamine
d)Coenzyme A                                                          
 Q.2-Choose the incorrect statement about Active Site of an enzyme-
a) The active site is a three-dimensional cleft
b) The active site takes up a large part of thetotal volume of an enzyme
c) Substrates are bound to enzymes by multiple weakattractions
d) The specificity of binding depends on theprecisely defined arrangement of atoms in an active site.
Q.3- Any of the following processes except one are involved at the active site of an enzyme to accelerate the rate of reaction-
a) Catalysis by BondStrain
b) Catalysis byProximity and Orientation
c) Non covalentcatalysis
d) Acid basecatalysis                                                  
 Q.4-A given substrate may be acted upon by a number of different enzymes, each of which uses the same substrate(s) and produces the same product(s). The individual members of a set of enzymes sharing suchcharacteristics are known as-
a)Group specific enzymes
c)Substrate specific enzymes
d)Allosteric enzymes
Q.5-A recently diagnosed hypertensive patient has been prescribed an ACE inhibitor(Angiotensin convertase inhibitor) which is known to act by lowering V max,what is the possible mechanism of inhibition of this drug?
b)Non Competitive
d)None of the above.
Q.6-Which statement out of the followings is incorrect about the effect of increasing temperature on enzyme activity-
a)Raising the temperature increases the kinetic energy of molecules
b) Aten degree Centigrade rise in temperature will increase the activity of mostenzymes by 50 to 100%.
c)Most animal enzymes rapidly become denatured at temperatures above 40oC
d)Storage of enzymes at 5°C or below is generally not suitable.
Q.7-A54-year –old male was rushed to emergency when he collapsed in the middle of abusiness meeting. Examination revealed excessive sweating and high bloodpressure.ECG chest was conclusive of Acute Myocardial infarction. Which biochemical investigation out of the followings would  be of no help inthe confirmation of diagnosis?
a) Cardiac Troponins
b)Serum myoglobin
c)Lactate dehydrogenase
d)Creatine Phospho kinase-MB(CPK-MB)
Q.8-A coal mine worker was brought in an unconscious state to emergency room aftera blast in the mine. His blood Carboxy hemoglobin level was high and he wasdiagnosed with CO poisoning.  CO is aknown inhibitor of electron transport chain. Which complex of electrontransport chain is inhibited by CO?
a)Complex I
b)Complex II
c)Complex III
d)Complex IV
Q.9-A 42-year-old obese female presented to theemergency center with complaints of worsening nausea, vomiting, and abdominal pain.Her pain was located in the midepigastric area and right upper quadrant. Blood biochemistry revealed high serum amylase level.What is the probable diagnosis for this patient?
a)Viral hepatitis
b)Acute Pancreatitis
c)Renal colic
d)Acute gastritis
Q.10-A 60 year old chronic alcoholic was brought to thehospital with complaints of protuberant abdomen (ascites) and edema feet. He also had history of hemorrhages.  Blood biochemistry revealed – High serumtransaminases, low Serum total proteins, Albumin and a prolonged prothrombintime. Urine analysis was normal. What could be the possible diagnosis?
a)Renal failure
b)Protein malnutrition
c)Cirrhosis of liver
d)Heart failure
Q.11-A 2 -week –old child was brought to theemergency. The parents were fearful that the child had been given some poisonas they noted black discoloration on the diaper. Adiagnosis of Alkaptonuria was made and the child was given Vitamin C as asupplement. Alkaptonuria occurs due to reduced activity of Homogentisic acid oxidaseenzyme. What is the role played by vitamin C in this defect?
a)Acts as an oxidant
b)Acts as a coenzyme
c)Acts as an inducer
d)Acts as a positive allosteric modifier
Q.12-A67- year-old army officer in good health previously presented with sudden painin the great toe.  Serum uric acid levelwas high, and a diagnosis of gouty arthritis was made He was advised bed rest,pain killers and Allopurinol. What is the mechanism of action of Allopurinol inlowering serum uric acid levels?
a)Suicidal inhibition
b)Non competitive inhibition
c)Allosteric inhibition
d)Feed back inhibition
Q.13-One out of the following enzymes has absolute specificity for its substrate; choose thecorrect option-
a) Urease
b) Carboxy peptidase
c) Pancreatic lipase
Q.14-Which out of the followings is a substrate-specific enzyme?
a) Hexokinase
c) Lactase
Q.15-Which out of thefollowings is not a substrate-specific enzyme?
 c) Hexokinase
Q.16-Group I Co enzymes participate in  which of the followingreactions-
a) Oxidation-reduction
c) Phosphorylation
d) All of the above
Q.17-Which out of thefollowing co enzymes takes part in hydrogen transfer reactions in the electron transport chain-
a) Tetrahydrofolate
b) Methyl Cobalamine
c)Co enzyme Q
d) Biotin
Q.18.The conversion of Pyruvate to oxaloacetate involves the participation of—-  as a coenzyme -
a) NAD+
c) Biotin
d) All of the above                                                        
Q.19- The drugFluorouracil is recommended for the treatment of cancers. It undergoes a seriesof changes and then binds to Thymidylate synthase enzyme resulting in itsinhibition and blockage of cell division. This mode of inhibition is mostprobably due to-
a) Allosteric inhibition
b) Competitive inhibition
c) NoncompetitiveInhibition
d) Suicidal inhibition                                                      
Q.20-The activities ofmany enzymes, membrane transporters and other proteins can be quickly activatedor inactivated by phosphorylation of specific amino acid residues. This regulation is called-
a) Allostericmodification
b) Covalent modification
c) Induction
d) Repression

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