Match the following
(A) Inhibitor of catalytic activity → (i) Ricin
(B) Possess peptide bonds → (ii) Malonate
(C) Cell wall material in fungi → (iii) Chitin
(D) Secondary metabolite → (iv) Collagen
Choose the correct option from the following:
(A)-(ii), (B)-(iv), (C)-(iii), (D)-(i)
(A)-(iii), (B)-(i), (C)-(iv), (D)-(ii)
(A)-(iii), (B)-(iv), (C)-(i), (D)-(ii)
(A)-(ii), (B)-(iii), (C)-(i), (D)-(iv)
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Consider the following statements:
(A) Coenzyme or metal ion that is tightly bound to enzyme protein is called a prosthetic group.
(B) A complete catalytically active enzyme with its bound prosthetic group is called an apoenzyme.
Select the correct option:
(A) is false but (B) is true.
Both (A) and (B) are true.
(A) is true but (B) is false.
Both (A) and (B) are false.
Enzymes could be simple or conjugated (holoenzyme). Conjugated enzymes are formed of two parts – a protein part called apoenzyme and a non-protein part named co-factor. Co-factors are bound to the enzyme to make it catalytically active. There are three types of cofactors: prosthetic groups, co-enzymes, and metal ions. Prosthetic groups are organic compounds and are distinguished from other cofactors in which they are tightly bound to the apoenzyme. Co-enzymes are organic compounds but their association with the apoenzyme is only transient, occurring during the course of catalysis. A number of enzymes require metal ions for their activity which form coordination one or more coordination bonds with the substrate.
Prosthetic groups differ from co-enzymes in that:
they require metal ions for their activity.
they (prosthetic groups) are tightly bound to apoenzymes.
their association with apoenzymes is transient.
they can serve as co-factors in a number of enzyme-catalyzed reactions.
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Which of the following statements is correct with reference to enzymes?
Holoenzyme = Apoenzyme + Coenzyme
Coenzyme = Apoenzyme + Holoenzyme
Holoenzyme = Coenzyme + Co-factor
Apoenzyme = Holoenzyme + Coenzyme
Holoenzyme is the complete conjugate enzyme consisting of an apoenzyme and a cofactor. Cofactor may be organic or inorganic in nature. Organic cofactors are of two types-coenzyme and prosthetic group.
A non-proteinaceous enzyme is:
Lysozyme
Ribozyme
Ligase
Deoxyribonuclease
A ribozyme is a ribonucleic acid (RNA) enzyme that catalyses a chemical reaction in a similar way to that of a protein enzyme. These are found in ribosomes and are also called catalytic RNAs.
Which of the following describes the given graph correctly?
Endothermic reaction with energy A in presence of enzyme and B in absence of enzyme.
Exothermic reaction with energy A in presence of enzyme and B in absence of enzyme.
Endothermic reaction with energy A in absence of enzyme and B in presence of enzyme.
Exothermic reaction with energy A in absence of enzyme and B in presence of enzyme.
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Which one of the following statements is incorrect?
The competitive inhibitor does not affect the rate of breakdown of the enzyme-substrate complex
The presence of the competitive inhibitor decreases the Km of the enzyme for the substrate.
A competitive inhibitor reacts reversibly with the enzyme to form an enzyme-inhibitor complex.
In competitive inhibition, the inhibitor molecule is not chemically changed by the enzyme.
Competitive inhibition is a reversible inhibition where the inhibitor competes with the normal substrate for the active site of the enzyme. A competitive inhibitor is usually chemically similar to the normal substrate and therefore fits into the active site of an enzyme and binds with it. The inhibition is thus due to a substrate analogue. The enzyme now cannot act upon the substrate, and reaction products are not formed. E.g., the activity of succinate dehydrogenase is inhibited by malonate. Km value or Michaelis constant is defined as the substrate concentration at which half of the enzyme molecules are forming enzyme-substrate (ES) complex or concentration of the substrate when the velocity of the enzyme reaction is half the maximal possible. A smaller Km value indicates greater affinity of the enzyme for its substrate; hence, shows a quicker reaction. The competitive inhibitor decreases the affinity of the enzyme for the substrate, thus increases the Km value.
