1. If enzyme code EC 2.6.1.1 belongs to aspartate amino transferase, then the code EC 4.3.1.3 belongs to which enzyme?
a) Chymosin
b) Histidase
c) Glucose oxidase
d) Glutathione synthetatase
Explanation: Enzyme commission by International Union of Biochemistry assigned each enzyme a recommended name and a 4 digit code. Code 4.3.1.3 belongs to histidase which is an example for lyase class of enzymes. The first digit codes for the main class of enzymes. The second digit codes for the type of enzyme catalyzed reaction whereas the third digit describes the enzyme catalyzed reaction. The fourth digit gives a number which keeps on changing as new enzymes are discovered.
2. Which of the following is a systematic name given by enzyme commission?
a) Renin
b) Aspartate aminotransferase
c) Glutathione synthetase
d) D-xylose ketol-isomerase
Explanation: International Union of Biochemistry appointed an “Enzyme commission” to provide proper systematic way of naming and classifying the enzymes. The commission assigned each enzyme a systematic name and a 4-digit code. D-xylose ketol-isomerase is a systematic name for glucose isomerase. Renin, Aspartate aminotransferase and glutathione synthetase are the common names of enzymes. L-aspartate: 2-oxoglutarate aminotransferase and g-L-glutamyl-L-cysteine: glycine ligase are systematic names for aspartate aminotransferase and glutathione synthetase respectively. Renin has not been given a systematic name till today.
3. Pick the odd one out of the following.
a) Decarboxylases
b) Dehydrogenases
c) Oxygenases
d) Peroxidases
Explanation: Dehydrogenases, oxygenases, peroxidases belong to oxidoreductases class of enzymes. These enzymes catalyze redox reactions which involves transfer of hydrogen or oxygen atoms or electrons between 2 molecules whereas decarboxylases belong to lyases class of enzymes which are involved in removal of atoms from substrates.
4. Which of the oxidoreductases are involved in oxygen transfer form molecular oxygen?
a) Peroxidases
b) Oxidases
c) Oxygenases
d) Dehydrogenases
Explanation: Oxidoreductases are the enzymes which are used during redox reaction, in which hydrogen atoms or oxygen atoms or electrons are transferred between molecules. Peroxidases transfer electrons to peroxides. As compared to Oxidases, which transfer electrons to molecular oxygen. Dehydrogenases are involved with transfer of hydrides. Oxygenases transfer oxygen from molecular oxygen to the substrate.
5. Which enzyme hydrolysis casein?
a) Chymosin
b) Glucose oxidase
c) Alanine aminotransferase
d) Histidase
Explanation: Casein is hydrolyzed to para-k-casein and caseino macropeptide by using chymosin which belongs to class of hydrolases. Glucose oxidase oxides glucose to D-glucono-1, 5-lactone. Alanine aminotransferase transfers amino group from alanine to form glutamate whereas histidase removes amino group from histidine to form urocanate.
6. What is the name of the following reaction?
Glucose-6-phosphate\(\underset{Glucose-6-phosphate \,isomerase}{\rightleftharpoons}\) Fructose-6-phosphate
a) Ligation reaction
b) Hydrolysis
c) Isomerization
d) Redox reaction
Explanation: The above reaction is isomerization reaction as it involves conversion between isomers of glucose with the help of an isomerase enzyme. Redox reaction involves transfer of hydrogen atoms or oxygen atoms or electrons between molecules with the help of oxidoreductases. Hydrolysis involves reaction utilizing water and hydrolases enzyme. Ligation reaction involves joining of 2 molecules with the help of ligases.
7. The class of enzymes which contains extensive group of enzymes are ____________
a) Ligases
b) Oxidoreductases
c) Aldolases
d) Esterases
Explanation: Oxidoreductases are the enzymes involved in the redox reactions and are the most extensive class of enzymes. As compared to ligases which have lesser number of enzymes. Aldolase and esterases belong to lyase and hydrolase class of enzymes.
8. Which class of enzymes contain relatively small group of enzymes?
a) Ligases
b) Oxidoreductase
c) Glutathione synthetase
d) D-xylose ketol-isomerase
Explanation: Ligases are the class of enzymes that contain small group enzymes as compared to oxidoreductases which contain extensive group of enzymes. Ligases are used in ligating two molecules coupled to breakdown of ATP or NTPs. Glutathione synthetase is an example of ligases and D-xylose ketol-isomerase is an example for isomerase class of enzymes. It’s commonly called glucose isomerase.
9. Substances which reduce the rate of enzyme catalyzed reactions are known as ____________
a) substrates
b) enzymes
c) products
d) inhibitors
Explanation: Certain substances may reduce the rate of enzyme catalyzed reactions. Some of these are non-specific protein denaturants (e.g., urea). While other substances which act in a fairly specific manner are referred to as inhibitors. Enzymes are biocatalyst which act on substrates to form products.
10. In the following diagram, which kind of inhibition is represented?
a) Uncompetitive inhibition
b) Competitive inhibition
c) Non-competitive inhibition
d) Mixed inhibition
Explanation: In the above diagram, it is shown that both substrate and inhibitor compete for the active site of the enzyme with formation of enzyme-inhibitor [EI] complex rather than enzyme-substrate-inhibitor [ESI] complex. Hence the inhibition shown in the diagram is competitive inhibition. It usually occurs at low substrate concentrations, but can be overcome at high substrate concentration.