Question

Study the given data and answer the questions that follow.

A sample of an enzyme called lactase was isolated from the intestinal lining of a calf. Assays were undertaken to evaluate the activity of the enzyme sample.

The substrate of lactase is the disaccharide lactose. Lactase breaks a lactose molecule in two, producing a glucose molecule and a galactose molecule. Two assays were carried out.

Assay 1

Lactose concentration (% w/v)	15	15	15	15	15	15
Concentration of enzyme sample(% v/v)	0	5	10	15	20	25
Reaction rate ($\mu$ mole glucose $se{c}^{-1}m{L}^{-1}$)	0	25	50	75	100	125

Assay 2

Lactose concentration (% w/v)	0	5	15	20	25	30
Concentration of enzyme sample(% v/v)	5	5	5	5	5	5
Reaction rate ($\mu$ mole glucose $se{c}^{-1}m{L}^{-1}$)	0	15	25	35	40	40

What are the variables in each of the two assays?

• A. Assay 1 - Lactose concentration
  Assay 2 - Concentration of enzyme sample
• B. Assay 1 - Concentration of enzyme sample
  Assay 2 - Lactose concentration
• C. Assay 1 - Lactose concentration
  Assay 2 - Lactose concentration
• D. Assay 1 - Concentration of enzyme sample
  Assay 2 - Concentration of enzyme sample

Answer 1

The correct option is B Assay 1 - Concentration of enzyme sample

Assay 2 - Lactose concentration
The concentration of enzyme sample changed/increased (varied) in Assay I, resulting in an increased rate of reaction from 0-125. while lactose concentration varied in Assay 2, the rate of reaction increased initially but was stable at lactose concentration 25 and 30.

So, the correct answer is 'Assay 1 - Concentration of enzyme sample

Assay 2 - Lactose concentration'