Question

What is the sign (positive or negative) of the entropy change for each of the following processes? In a sentence or two, explain your answer.

A) water freezes

B) water evaporates

C) sodium chloride dissolves in water

D) several different types of lipid molecules assemble to form a membrane

E) a cell oxidizes glucose in order to obtain energy for cellular work

2) The role of an enzyme in an enzyme-catalyzed reaction is to:

A) ensure that the product is more stable than the substrate

B) increase the rate at which substrate is converted to product

C) ensure that all the substrate is converted to product

D) B and C are correct

E) all are correct

Then, explain the parameters or “rules” for enzyme function

Answer 1

1. A) water freezes: Negative

B) water evaporates: Positive

C) sodium chloride dissolves in water: Positive

D) several different types of lipid molecules assemble to form a membrane: Negative

E) a cell oxidizes glucose in order to obtain energy for cellular work: Positive

The positive sign represent the increase in entropy or randomness. Freezing water reduces entropy, water evaporation increases entropy and dissolving salt in water leads to increase in entropy. Formation of membrane from lipid molecule rearrange the molecules in a more ordered form and reduces entropy. Oxidation of glucose to generate energy increases entropy.

2. The correct option is B) increase the rate at which substrate is converted into product.

Enzyme increases the rate of reaction by reducing the activation energy.