Photosynthesis

Photosynthesis

‘Life is a tiny electric current kept moving by the sun’

Svent Gorki

Protocista

Algae Plants

Photosynthesis Equation

carbon dioxide + water glucose + oxygen

6CO2 + 6H20 C6H1206

White Light

Electro magnetic spectrum

So Why Green?

Chloroplasts

Chlorophyll

Chlorophyll plays an important role in photosynthesis as it

absorbs the energy form the sun

Fluorescence of extracted chlorophyll

Absorption and action spectrum of chlorophyll

Light IndependentStage

6 CO2

6H2OC6H12O6

24 H 6O2

Oxygen produced

12H2O

SUN

Chlorophyll

Water used

Lightdependent

Stage

Measuring the rate of photosynthesis

Extraction of chlorophyll and absorption spectrum

Assessment - Data Collection and Processing, Conclusion and Evaluation, manipulative skills

Extraction of chlorophyll

• Dip fresh leaf material into boiling water first to kill the cells and to make the cell membrane fully permeable to the solvent.

• Finely cut about 10g of leaf material (excluding the midrib and petiole) into a mortar and add a small amount of washed and dried sand.

• Grind up the leaf matter with 20cm3 of propanone, using a pestle, to make a concentrated leaf extract.

• Either filter the pigment solution or decant it (using a glass rod to hold back the debris), and place in a small glass centrifuge tube. Centrifuge the extract briefly, in order to clear all suspended organic matter.

• Pour the supernatant solution into a small glass tube, seal with a bung, label it, and stand this chlorophyll extract in the dark, an ice bath, until required.

Measuring absorption of light by chlorophyll

• You will be shown how to use either a colorimeter or a

spectrophotometer to measure the absorption spectrum of your extract. Once you have done this you will need to plot a graph of absorption against wavelength for the data you collected.

• • Compare this to the absorption and action spectrums of chlorophyll.

How good is your match and how could the experiment be altered to improve your results.