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Multiple Choice Questions- Enzymology
Q.1- Glycogen phosphorylase, which mobilizes glycogen for energy, requires which of the following 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 the total volume of an enzyme
c) Substrates are bound to enzymes by multiple weak attractions
d) The specificity of binding depends on the precisely 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 Bond Strain
b) Catalysis by Proximity and Orientation
c) Non-covalent catalysis
d) Acid-base catalysis
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 such characteristics are known as-
a) Group-specific enzymes
b) Isoenzymes
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?
a) Competitive
b) Non -competitive
c) Uncompetitive
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) A ten-degree Centigrade rise in temperature will increase the activity of most enzymes by 50 to 100%.
c) Most animal enzymes rapidly become denatured at temperatures above 40oC
d) The storage of enzymes at 5°C or below is generally not suitable.
Q.7-A 54-year –old male was rushed to the emergency when he collapsed in the middle of a business meeting. Examination revealed excessive sweating and high blood pressure.ECG chest was conclusive of Acute Myocardial infarction. Which biochemical investigation out of the following would be of no help in the 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 the emergency room after a blast in the mine. His blood Carboxyhemoglobin level was high and he was diagnosed with CO poisoning. CO is a known inhibitor of the electron transport chain. Which complex of electron transport 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 the emergency center with complaints of worsening nausea, vomiting, and abdominal pain. Her pain was located in the mid epigastric area and right upper quadrant. Blood biochemistry revealed a 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 the hospital with complaints of the protuberant abdomen (ascites) and edema feet. He also had a history of hemorrhages. Blood biochemistry revealed – High serum transaminases, low Serum total proteins, Albumin and prolonged prothrombin time. 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 the emergency. The parents were fearful that the child had been given some poison as they noted black discoloration on the diaper. A diagnosis of Alkaptonuria was made and the child was given Vitamin C as a supplement. Alkaptonuria occurs due to reduced activity of the Homogentisic acid oxidase enzyme. 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-A 67- year-old army officer in good health previously presented with sudden pain in the great toe. Serum uric acid level was 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 in lowering serum uric acid levels?
a) Suicidal inhibition
b) Noncompetitive inhibition
c) Allosteric inhibition
d) Feedback inhibition
Q.13-One out of the following enzymes has absolute specificity for its substrate; choose the correct option-
a) Urease
b) Carboxy peptidase
c) Pancreatic lipase
d)Lipoprotein lipase
Q.14- Which out of the following is a substrate-specific enzyme?
a) Hexokinase
b)Thiokinase
c) Lactase
d) Decarboxylase
Q.15-Which out of the following is not a substrate-specific enzyme?
a) Glucokinase
b) Fructokinase
c) Hexokinase
d) Phospho fructokinase
Q.16-Group I Coenzymes participate in which of the following reactions-
a) Oxidation-reduction
b)Transamination
c) Phosphorylation
d) Carboxylation
Q.17-Which out of the following coenzymes takes part in hydrogen transfer reactions in the electron transport chain-
a) Tetrahydrofolate
b) Methyl Cobalamine
c) Coenzyme Q
d) Biotin
Q.18.The conversion of Pyruvate to oxaloacetate involves the participation of—- as a coenzyme –
a) NAD+
b) NADPH
c) Biotin
d) FAD
Q.19- The drug Fluorouracil is recommended for the treatment of cancers. It undergoes a series of changes and then binds to the thymidylate synthase enzyme resulting in its inhibition and blockage of cell division. This mode of inhibition is most probably due to-
a) Allosteric inhibition
b) Competitive inhibition
c) Noncompetitive Inhibition
d) Suicidal inhibition
Q.20-The activities of many enzymes, membrane transporters, and other proteins can be quickly activated or inactivated by phosphorylation of specific amino acid residues. This regulation is called-
a) Allosteric modification
b) Covalent modification
c) Induction
d) Repression
Key to answers
1)-a
2)-b
3)-c
4)-b
5)-b
6)-d
7)-c
8)-d
9)-b
10)-c
11)-b
12)-a
13)-a
14)-c
15)-c
16)-a
17)-c
18)-c
19)-d
20)-b