REQUIRED PRACTICAL 8

Question 1

What is the function of dehydrogenase activity in chloroplasts?

Answer 1

Catalyses the acceptance of electrons by NADP in the light dependant reaction(LDR).

Question 2

What is the purpose of DCPIP?

Answer 2

A redox indicator dye and acts as an alternate electron acceptor instead of NADP.

turns from BLUE to COLOURLESS when reduced.

Question 3

Why is the plant extract chilled in an ice-wate bath?

Answer 3

To lower the activity of enzymes to prevent them from breaking down the chloroplasts.

Question 4

How is the control set up?

Answer 4

Fill a cuvette with chloroplast extract and distilled water.

Question 5

How is light intensity controlled?

Answer 5

Adjust the distance of the lamp from the set up.

Perform the practical in a dark room so that the only light source is the lamp.

Question 6

What is the function of the muslin cloth?

Answer 6

To filter out any debris in the ground leaf mixture but allowing chloroplasts to pass through.

Question 7

Why are the stalks of leaves removed before grinding?

Answer 7

The stalks dont contain many chloroplasts.

Question 8

Outline the procedure of investigating the effect of light intensity, after chloroplast extract has been obtained?

Answer 8

1. set the colorimeter to the red filter. Zero using a cuvette containing chloroplast extract and distilled water.
   2.Place test tube in the rack 30 cm from a light source and add DCPIP.
2. Immediately take a sample and add to cuvette. measure absorbance of the sample.
3. Take a sample and measure it’s absorbance every 2 min for 10 minutes .
4. Repeat for different distances from the lamp up to 100 cm.