enzyme application

Question 1

Before starting their experiments, the scientists confirmed that, like human breast milk, cat’s milk also contained bile-activated lipase.

To do this, they added bile to cat’s milk and monitored the pH of the mixture.

Explain why monitoring the pH of the mixture could show whether the cat’s milk contained lipase.

Answer 1

Hydrolysis of lipids produces fatty acids;

2. Which lower pH of mixture.

Question 2

A student investigated the effect of lipase concentration on the hydrolysis of lipids.

He took a beaker containing a suspension of lipids. He placed a pH probe attached to a data logger into the beaker. After 5 minutes, he added the lipase solution. The data logger recorded the pH. The apparatus used is shown in the diagram below.

The student repeated the experiment with a higher concentration of lipase solution.

choose a suitable control

Describe and explain the results you would expect him to get.

Answer 2

Boiled lipase solution;

Faster fall in pH and levels off at same point;

2. More enzyme = substrate complexes formed;
3. Same amount of fatty acids produced / product

Question 3

Explain the shape of the curve between 30 °C and 50 °C. enzyme rate is decreasing

Answer 3

Enzyme denatured / hydrogen bonds / bonds holding tertiary structure broken / tertiary structure changed;

2. Change in shape of active site (of enzymes);
3. Substrate / protein no longer fits / binds (into active site) / few or no ES complexes;

Question 4

Bacteria produce enzymes which cause food to decay. Explain how vinegar, which is acidic, can prevent the action of bacterial enzymes in some preserved foods.

Answer 4

bacterial) active site / enzymes / proteins denatured /
tertiary 3D structure disrupted / changed;
(ionic) bonds broken;

(reject peptide bonds)
(ignore other bonds)

no enzyme substrate complex formed / substrate no longer fits;

Question 5

Gelatine is a protein. When a warm gelatine solution cools, it sets to form a jelly.
Fresh pineapple juice contains an enzyme that digests protein.
A student investigated the effect of pineapple juice on the setting of jelly.
He set up three different tubes of warm gelatine solution and recorded which had set after three hours. The contents of each tube and his results are shown in the table.

Tube

Contents of tube

Jelly formed

A

6 cm3 gelatine + 2 cm3 pineapple juice + 2 cm3 water

No

B

6 cm3 gelatine + 2 cm3 pineapple juice + 2 cm3 hydrochloric acid

Yes

C

6 cm3 gelatine + 2 cm3 boiled pineapple juice + 2 cm3 water

Yes

What was the purpose of tube C?

Answer 5

For comparison / as a control;

To show that it is an enzyme in pineapple that digested gelatine /
stopped gelatine setting in tube 1;

Boiling denatures enzyme / Can be described but must be
permanent change;

Other components of pineapple still present;