PS Exps.

Question 1

What is the role of dehydrogenase in chloroplasts?

Answer 1

To help reduce NADP.

NADP is the final e- acceptor in the ETC
→ the reaction is catalysed by dehydrogenase.

Question 2

How does the exp. to investigate the activity of dehydrogenase work?

Answer 2

• The activity of this enzyme can be investigated using a colorimeter and by adding a redox indicator dye to extracts of chloroplasts.
• Like NADP, the dye acts as an electron acceptor and gets reduced by the dehydrogenase in the chloroplasts. As the dye gets reduced, you’ll see a colour change.
• You can measure the rate of the dehydrogenase activity by measuring the rate at which the dye loses its colour using a colorimeter.
• A colorimeter measures how much light a solution absorbs when a light source is shone directly through it. A coloured solution absorbs more light than a colourless solution.

Question 3

Method for investigating the activity of dehydrogenase (exp.).

Answer 3

Question 4

What results would you expect if dehydrogenase activity is taking place?

Answer 4

If dehydrogenase activity is taking place, the absorbance will decrease as the DCPIP gets reduced and loses its blue colour.

• Th faster the absorbance decreases, the faster the rate of dehydrogenase activity.