IGCSE Biology Paper-1: Specimen Questions with Answers 122 - 122 of 208

The figure given below shows the conversion of a substrate into product by an enzyme. In which one of the four option (A-D) the components of reaction labelled as P, Q, R and S are identified correctly.

The Figure Given below Shows the Conversion of a Substrate into Product by an Enzyme

	P	Q	R	S
A	Activation energy with enzyme	Transition state	Activation energy without enzyme	Potential Energy
B	Potential Energy	Transition state	Activation energy without enzyme	Activation energy with enzyme
C	Transition state	Potential Energy	Activation energy without enzyme	Activation energy with enzyme
D	Potential Energy	Activation energy with enzyme	Transition state	Activation energy without enzyme

Answer

b.

Explanation

Enzymes Speed up Reactions

The chemical reactions require a certain amount of energy to initiate which is called as activation energy or free energy for the activation. A cell has several substrates, which have average kinetic energy, in which some have higher and some lower than the average energy. In normal temperature, the molecules with high energy react to form the product. This is a slow process. The increase in the reaction rate is due to the raise in the mixture temperature. The heat increases the molecular kinetic energy that causes collisions and reaction between them. Enzyme fastens the reaction as it lowers the required activation energy and allows several numbers of molecules to react at time. It is a known fact that the enzymes have substrate slot where it combines and bring several similar ones closer which collide in the most suitable location and directions where the reaction occurs. The inorganic catalysts work in the same manner. When the substrate binds to the enzymes, there is a conformational change in the enzyme active sites that actually “push” or let a substrate molecule to start an interaction.