Practical 8

Question 1

what is the function of dehydrogenase in chloroplasts

Answer 1

it catalyses the acceptance of electrons by NADP in LDR

Question 2

what is the purpose of DCPIP

Answer 2

it is a redox indicator dye and acts as an alternate electron acceptor instead of NADP. it turns from blue to colourless when reduced

Question 3

why is the plant extract chilled in an ice water bath

Answer 3

to lower the activity of the enzymes to prevent them 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

what are the stalks of leaves removed before grinding

Answer 7

the stalks do not contain many chloroplasts

Question 8

outline the procedure of investigating the effect of the light intensity after chloroplast extract has been obtained

Answer 8

1. set the colorimeter to the red filter. zero using a cuvette contains chloroplast extract and distilled water
2. place test tube in the rack 30cm from source and add DCPIP. immediately take a sample and add to cuvette. measure the absorbance of the sample
3. take a sample and measure it absorbance every 2 minutes for 10 minutes
4. repeat for different distances from the lamp