Question

In a biphasic system, the thickness of the aqueous layer (δ) around an immobilised enzyme lowers the rate of reaction.

(a) True

(b) False

I got this question in a national level competition.

The question is from Recent Advances topic in section Recent Advances in Enzyme Technology of Enzyme Technology

Answer 1

Correct answer is (a) True

Explanation: In biphasic systems, reactants may have fairly low aqueous solubilities under normal conditions. The aqueous phase remains effectively unstirred, while the organic phase is well-stirred so that the thickness of the ‘unstirred layer’ (δ) is equal to the thickness of the aqueous layer surrounding the enzyme.

• When δ is large, it leads to the passage of reactants through aqueous layer due to formation concentration gradient which will be very shallow. This the result of the reactants being less soluble in water.

• If δ is small, the enzyme is freely soluble, causing the reactants from the more concentrated organic phase through the interphase boundary to very low concentrations within the microenvironment of the enzyme.

This shows that the thickness of the aqueous layer around an immobilized enzyme is important and determines the degree of diffusional resistance involved. Thus, lowering the reaction rate. Hence the above statement is true.