the effect of ammonium hydroxide on the time taken for chloroplasts to decolourise DCPIP - 8

Question 1

REQUIRED PROCTICAL 7:
an investigation into the effect of a named factor on the rate of dehydrogenase activity in extracts of chlorophyll

the effect of ammonium hydroxide on the time taken for chloroplasts to decolourise DCPIP

Answer 1

an investigation into the effect of a named factor on the rate of dehydrogenase activity in extracts of chlorophyll

the effect of ammonium hydroxide on the time taken for chloroplasts to decolourise DCPIP

Question 2

Why does DCPIP change from blue to colourless?

Answer 2

when DCPIP accepts electrons released by the chlorophyll

Question 3

what does ammonium hydroxide act like?

Answer 3

affects the LDR in photosynthesis - in a similar way to many week killers

Question 4

what is the equipment list for this practical?

Answer 4

• spinach leaves
• blender
• measuring cylinder
• muslin (filtering)
• filter funnel
• 3 beakers
• ice
• isolation medium (cold)
• DCPIP solution (cold)
• distilled water (cold)
• ammonium hydroxide solution (cold)
• test tubes (5)
• test tube rack
• syringes (1cm^3 and 5^cm)
• piece of aluminium foil
  -lamp
• marker pen
• timer

Question 5

what is the method?

Answer 5

1. 50cm^3 of isolation medium into a beaker
2. tear 8 spinach leaves into small pieces and place into isolation medium. (do not but midribs or leaf stalk)
3. half fill a large beaker with ice and place a small beaker on top
4. put 3 layers of muslin over the top of the filter funnel and wet it with isolation medium . rest the filter funnel is the small beaker on the ice
5. pour the spinach and isolation medium into the blender and blend for about 15 sec. pour the blended mixture back into the beaker
6. pour a little of your blended mixture through the muslin in the filter funnel. carefully fold and squeeze the muslin to assist the filtering process. repeat until most of the blended mixture has been filtered. label this filtrate which is in the small beaker on ice as ‘chloroplast suspension’
7. Set up 5 test tubes labelled A,B,C,X,Y
8. A- DCPIP solution, water and chloroplast suspension in dark (cover aluminium foil)
9. B - DCPIP solution, water and isolation medium.
10. C- water + chloroplast suspension - help determine when colour change is complete
11. X - DCPIP and Water and chloroplast suspension, place in light (lamp)
12. Y - DCPIP and Ammonium hydroxide and chloroplast suspension. record colour change

Question 6

What were the results?

Answer 6

Only tube X changed colours from blue to green