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A2 Biology BY4

Barbara Lipscombe

on 13 July 2017

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Transcript of Photosynthesis

Green light is transmitted (passes through) or reflected
is a mixture of many
The similarity of the action and absorption spectra provide evidence that the pigments are used during photosynthesis
Non cyclic
The Calvin Benson cycle
A summary of Photosynthesis
An overview
Photosynthetic pigments
Chlorophyll a
Hydrophobic hydrocarbon chain in membrane
Mg at centre of porphyrin ring that can loose an electron

Carotene – an accessory pigment
Absorbs energy at wavelengths not absorbed by chlorophyll
Does not loose electrons
Absorption and Action Spectra
Leaves are Green
The site of photosynthesis
In the 1950's Melvin Calvin and Andrew Benson did experiments designed to find the first products of photosynthesis after CO2 fixation. Calvin won the Nobel Prize in Chemistry in 1961 for this work.
Experiments by T. W. Engelmann in the 1880s demonstrated action spectra
Algal beads practical
Separation of photosynthetic pigments by paper chromatography
Using the hydrophyte Cabomba.
Bubbles of oxygen released as the plant photosynthesises are counted to give a measure of the rate of photosynthesis
The effect of light intensity on the rate of photosynthesis
Fluorescence of Chlorophyll
Chlorophyll is bound to thylakoid membranes in the chloroplasts, where absorbed photons of light excite electrons and are converted to chemical energy. When chlorophyll is extracted from chloroplasts, light energy cannot be transferred and converted, so the light is re-emitted as fluorescence.

Cyclic photophosphorylation
after 2 hours
covered with different filters
CO2 concentration falls in proportion to rate of photosynthesis
before algal beads added
exposed to air with 4% CO2
Peter Mitchell proposed the theory of chemiosmosis while working with Jennifer Moyle at his reseach lab near Bodmin. He recieved the Nobel prize for his work in 1978
Calvin/Benson results
Chromatography -after algae have been exposed to C 14
carbon fixation
reduction of GP
regeneration of RuBP
Full transcript