Reference no: EM132219947

Leaf Structure and an Investigation of the Photochemical Reactions of Photosynthesis

Part 1: The structure and function of the leaf

Draw 5 -10 cells in each layer and then continue the layer with a line. Repeat this from the top layer to the bottom of the leaf. If you cannot observe a particular structure, indicate that with a star at the bottom of the page.

Question 1: In which tissue layer of the leaves are the chloroplasts located?

Question 2: Explain the difference in distribution of chloroplasts within the leaves between the two samples.

Part 2: Photochemical reactions of photosynthesis

Questions to consider during the experiment

- Is oxygen produced as a result of carbon fixation or of electron transport?
- Can electron transport continue to produce NADPH if there is no CO2? Why or why not?

Assay optimisation.

1. Place a ruler on the bench.

1. Place the desk lamp at the end of the ruler. Make sure that the lamp is turned off .

2. Take a lump of Blu Tack and stick a l ine of i t on the bench at 26 cm from the ruler.

3. Take 2 plastic cuvettes, or glass tubes, and label them C (Control) and E (Experimental) (at top & on the f rosted side i f cuvettes used).

4. Add buffer and DCPIP solutions to the tubes as per the table below.

	Buffer (µ L)	DCPIP (µ L)
Control (C)	1,100	0
Experimental (E)	950	150

5. Add 50 µL of chloroplasts to each tube. Quickly mix the solutions by covering the tubes with a piece of Parafilm and inverting.

6. Turn on the lamp and start the timer at the same time.

7. By observing the tubes, measure the time taken for the contents of the experimental tube to turn the same colour as the control. (The colour should change from blue to green)

Question

How much time did it take for the colour of the experimental tube to change from blue to green? Using this time as a guide, deduce the time required for your own measurements and a sampling regime for the experiments you will now perform.

Your Experimental Assay

1. Place a ruler on the bench.

2. Place the desk lamp at the end of the ruler. Make sure that the lamp is turned off .

3. Take a lump of Blu Tack and stick a l ine of i t on the bench at 26 cm from the ruler.

4. Take three cuvettes, or glass tubes, and label them C, DC and E, at top, & on the frosted side if cuvettes used. C, DC and E respectively stand for Control, Dark Control, Experimental. Are there other controls you wish to run? I f so, include them in your experiment.

5. Add buffer and DCPIP solution as per the table below

	Buffer (µ L)	DCPIP (µ L)
Control (C)	1,100	0
Dark control (DC)	950	150
Experimental (E)	950	150

6. Read the absorbance of the control ( C) at 590nm. What does this absorbance represent?

7. Place tubes on the Blu Tack. Cover the dark control with a foil tent.

8. To all tubes, add 50 µL (you may be asked to add a different amount as the chloroplast concentration of chloroplast solution can vary), mix thoroughly by covering the tubes with a piece of Parafilm and inverting.

9. Quickly read the absorbance (590 nm) of the tubes and return them to the Blu Tack. Cover the dark control tube with a foil tent.

10. Turn on the lamp and the timer at the same time.

11. Expose the control and experimental tubes to l ight for a period determined in optimization.

12. Turn off the l ight.

13. Read the absorbance of the control, experimental and dark control tubes.

14. Return the tubes to the Blu Tack. Remember to cover the dark control tube with foil.

15. Repeat steps 9 to 14 until you reach your optimised time of DCPIP reduction.

16. Enter your absorbances into the table.

Attachment:- Manual Practical.rar