Question

Enzyme facilitates a reaction through
A. Reduction in activation energy
B. Increase in activation energy
C. Altering pH
D. Altering temperature

Answer 1

Enzymes are catalysts that increase the rate of reaction by lowering the energy making the transition of the substrate to product more easily.

Complete answer: The activation energy is the difference in the average energy content of a ‘substrate’ from that of the transition state. Enzymes increase the rate of reaction by lowering the activation energy making the transition of the substrate to product more easily. The reaction is said to be exothermic if the product is at a lower level than the substrate. One need not supply energy (by heating) to form the product. Enzymes are proteinaceous (except RNA enzymes) and have a tertiary structure. They have high molecular weight so they exist in crystal or colloidal form. Enzymes do not initiate a chemical reaction. They have low activation energy and they remain unchanged at the end of the reaction. Enzymes are substrate and reaction specific and work at a particular pH and temperature.
Enzymes work at an optimum temperature of 25-40 degree Celsius. At low temperature, enzymes get inactivated and at high temperature, they get denatured (peptide bonds get denatured). There are some enzymes which are temperature resistant. Example- enzymes of microorganisms living in hot springs up to 40-45 degree Celsius and then start decreasing because of the molecular configuration of enzymes changes due to breaking of electrostatic forces and bonds between molecules.

Note: Enzymes are generally globular proteins, acting alone or in larger complexes. The sequence of the amino acids specifies the structure which in turn determines the catalytic activity of the enzyme. They are usually much larger than their substrates.