Photosynthesis

Question 1

what is the principle of paper chromatography?

Answer 1

the more soluble substances will travel further in a solvent that is moving through chromatography paper.

Question 2

what are the steps when preparing the chromatogram?

Answer 2

-paper should drop just below the base of the tank and into the volume of solvent used.
-horizontal line should be drawn in PENCIL a few centimeters above the base of the chromatogram. (should lie above the solvent.
-the solution containing the plant pigment should be spotted on the pencil line.
-process is repeated to concentrate the spot.
-spot should be small and avoid contamination of the chromatogram (only touch corners and don’t set down on bench)

Question 3

what are the steps when running the chromatogram?

Answer 3

-chromatogram is carefully suspended into the solvent and attached to the lid of the tank
-ensure line and conc. spots don’t touch the solvent
-ensure chromatogram is securely attached
-ensure chromatogram is not suspended at an angle

Question 4

how is the chromatogram developed?

Answer 4

-should then be dried
-before solvent is dried, solvent front should be marked with a pencil

Question 5

what is an Rf value?

Answer 5

the distance moved by the solvent
__________________________
distance moved by the solute

Question 6

how is the Rf value calculated?

Answer 6

-measuring the distance from the origin to the position of the solvent front
-measuring the distance from the origin spot to the position of the plant pigment being investigated.

Question 7

what redox indicator picks up electrons and changes colour as it does so?

Answer 7

DCPIP

Question 8

what colour does DCPIP change when it becomes reduced?

Answer 8

from blue to colourless

Question 9

what is the procedure for demonstrating the role of hydrogen acceptors in photosynthesis using redox indicators?

Answer 9

-place 5g chopped lettuce into a mortar with 10cm3 of buffer solute and grind with a pestel
-pour contents through a muslin filter into a beaker
-pour suspension into a centrifuge
-centrifuge at a high speed for 10-12 minutes
-pour off and discard of the supernatant of the centrifuge tubes (will remove organelles smaller than chloroplasts)
-chloroplasts from centrifuge can be added to two experimental test tubes which have buffer added to them
-one is covered with foil (to prevent light reaching the chloroplasts)
-a third tube is set up with buffer and no chloroplasts
-DCPIP is added to each tube and placed in a beaker of crushed ice
-beaker containing the tubes is placed under a very strong light source and the colour is examined every 5 minutes for 20 minutes.