Practical 11: Photosynthesis and the Hill reaction

Question 1

Photosynthesis and the Hill reaction

Answer 1

1. Remove stalks from leaf samples. Cut into small sections. Grind sample using a
   pestle and mortar and place into a chilled isolation solution.
2. Place several layers of muslin cloth into funnel and wet with isolation medium to
   filter sample into a beaker.
3. Suspend the beaker in an ice water bath to keep sample chilled.
4. Transfer to centrifuge tubes and centrifuge at high speed for 10 minutes. This
   will separate chloroplasts into the pellet.
5. Remove supernatant and add pellet to fresh isolation medium.
6. Store isolation solution on ice.
7. Set the colorimeter to the red filter. Zero using a cuvette containing chloroplast
   extract and distilled water.
8. Place test tube in rack 30cm from light source and add DCPIP. Immediately take
   a sample and add to cuvette.
9. Measure the absorbance of the sample using the colorimeter
   10.Take a sample and measure its absorbance every 2 minutes for 10 minutes.
   11.Repeat for different distances from lamp up to 100 cm. This will vary the light intensity

risks- DCPIP, lamps

variables-
control = time in centrifuge
independent = leaf samples
dependent = level of absorbance

plot data in a table