Role of redox indicators in photosynthesis

Question 1

At what stage is photosynthesis does this occur and what happens?

Answer 1

During the light-dependent stage, electrons are energised to reduce NADP to reduced NADP.

Question 2

What is used and whats the colour change?

Answer 2

DCPIP is used and when it becomes reduced it changed from Blue to colourless.

Question 3

Describe the procedure.

Answer 3

1) Place 5g of chopped lettuce in a mortar. Add 10cm³ of buffer solution and grind with pestle.
2) Pour contents through muslin and filter into a beaker.
3) Pour contents into centrifuge tubes, remember the counterbalance tubes.
4) Centrifuge at high speed for 10-12 minutes.
5) Discard supernatant. Remove organelles smaller than chloroplasts.
6) Sedimented chloroplast are added to two tubes, A and B. Add buffer to both. Cover one with foil. Have a 3rd one with buffer only - control
7) Add DCPIP to all, place in a beaker of crushed ice
8) Place in a v.strong light source, colour of each examined every 5 mins for 20 mins

Question 4

What will happen in A - Chloroplasts, light and DCPIP
B - Chloroplasts and DCPIP
C - Water and DCPIP

Answer 4

A - Blue to Green (chloroplasts are green)
B - Remain blue-green ( no light)
C - Nothing.

Question 5

Why are chloroplasts isolated?

Answer 5

Because plants contain mitochondria which are smaller than chloroplasts and will reduce DCPIP aswell.