Biomolecules Test - 45

Sucrose is not an example of hydrolases. Sucrose, commonly named table sugar or sugar, is cane and beet sugar. The molecule is a disaccharide combination of the monosaccharides glucose and fructose with the formula C$$_{12}$$H$$_{22}$$O$$_{11}$$. On the other hand hydrolase is an enzyme that catalyzes the hydrolysis of a chemical bond. So, sucrose is not a hydrolase.

Solution:

Correct answer is option A.
Explanation for correct option:

• The catalytic efficiency of two different enzymes can be compared by comparing their K$$_m$$ value or Michaelis Menten constant. The Michaelis constant is the substrate concentration at which the reaction rate is at half-maximum. 
  
• The K$$_m$$ describes the affinity of the enzyme for a substrate molecule.  Greater the affinity lower is the K$$_m$$ value and sooner the V$$_{max}$$ can be attained and vice versa.

The Michaelis constant (K$$_m$$) of an enzyme is the substrate concentration at which the reaction rate is one-half the V$$_{max}$$. An enzyme with a high K$$_m$$ has a low affinity for its substrate, and requires a greater concentration of substrate to achieve V$$_{max}$$.

K$$_m$$ denotes the Michaelis constant. K$$_m$$ is the concentration of substrate at which half the active sites are filled. Thus, K$$_m$$ provides a measure of the substrate concentration required for significant catalysis to occur. For most of the enzymes, K$$_m$$ is assumed to approximate the substrate concentration at which reaction rate is one half the maximum. K$$_m$$ value can be used to compare rate of enzyme catalysis of two different enzymes. Lesser the K$$_m$$ value, faster the enzyme.

Enzymes are the biocatalyst. Most of the enzymes have been classified into different groups based on the type of reactions they catalyze. They are as follows-
(i) Oxidoreductases/ dehydrogenases: The enzymes catalyzing oxidation and reduction between two substrates S and G involving gain or loss of electrons are known as dehydrogenases.

(ii) Transferases: The enzymes catalyzing  the transfer of a group, G (other than hydrogen) between a pair of substrate S and S are known as transferases.

(iii) Hydrolases: The enzymes catalyzing hydrolysis of ester, ether, peptide, glycosidic, C-C, C-halide or P-N bonds are known as hydrolases.

(iv) Lyases: The enzymes that catalyzes the removal of groups from substrates by mechanisms other than hydrolysis leaving double bonds are known as Lyases.

(v) Isomerases: The enzymes that catalyzes inter-conversion of optical, geometric or positional isomers are known as isomerases.

(vi) Ligases:The enzymes catalyzing, the linking together of 2 compounds are known as ligases.
So, the correct answer is option B.

• Enzymes are proteinaceous in nature. There are intra and intermolecular bonds that hold proteins in their secondary and tertiary structures. 
• The increase in the temperature over an optimum range leads to the disruption of bonds. This makes the enzymes sensitive to heat.

So the correct answer is option C.

Solution :

For an enzyme catalyzed reaction, which follows Michaelis-Menten kinetics, the substrate concentration at which V$$_0$$ (initial rate or initial velocity), is half maximal is defined as K$$_m$$, the Michaelis constant.

A cofactor is a non-protein chemical compound or metallic ion which is required for the brisk activity of the enzyme. Vitamins acts as a precursor for many organic cofactors like vitamins B1, B2, B6, B12, niacin, folic acid) or as coenzymes themselves (e.g., vitamin C).