F214: Photosynthesis revision notes

Detailed revision note for photosynthesis, specific to the F214 OCR exam. I hope this helps :)

(All ideas and definitions from Heinemann OCR Biology text book)

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  • Created by: Jess
  • Created on: 02-01-13 16:17
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Autotrophs: organisms that convert inorganic carbon into organic carbon using light or chemical energy.
Heterotrophs: ingest organic carbon molecules.
Photosynthesis: transfers light energy into the chemical potential energy of organic molecules.
6CO2 + 6H2O C6H12O6 + 6CO2
Large surface area for pigments, electron
carriers and ATP synthase.
Chlorophyll absorbs light.
Has a double membrane with transport proteins
to control entry and exit and had electron
Photosynthetic pigments are arranged in
photosystems to allow maximum light
Protein embedded in the grana hold the
photosystems in place.
Stroma contains enzymes needed for the light
dependent stage.
Grana are surrounded by stroma so products
form the light dependent stage can pass easily
into the stroma.
They have their own DNA and ribosomes to
make proteins.
Photosynthetic pigment: they absorb light energy. Each absorbs their own range of wavelength as
they have their own peak of absorption.
Chlorophyll - long phytol chain and porpyrin (contains Mg)
a: - P680 and P700 ­ yellow-green and absorbs red light.
Found in the primary pigment centre.
P680: photosystem II with max wavelength at 680nm
P700: photosystem I with max wavelength at 700nm.
Also absorbs blue light at 450nm.
b: absorbs wavelengths around 500nm and 640nm. It appears blue-green.
Accessory pigments
Carotenoids reflect yellow/orange light and absorb blue light.
They absorb wavelengths that aren't absorbed by chlorophyll.
Carotene and xanthophyll are the main carotenoid pigments.

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Light Dependent Stage ­ thylakoid membrane.
Photolysis: 2H2O 4e- + 4H+ + O2
Light energy is absorbed by PSII (chlorophyll a ­ P680nm).
2e- become excited and breaks away from Mg.
2e- is carried to an electron acceptor by increasing energy levels.
2e- is transported to PSI by electron carriers.
ATP synthase converts ADP +Pi ATP
At the same time light energy is absorbed by PSI (chlorophyll a P700nm).
2e- become accepted and travel to another electron acceptor.…read more

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Chemiosmosis: the flow of protons down a proton gradient through channels in ATP synthase, from the thylakoid
space into the stroma.
Light strike PSII and 2e- become excited.
Electrons are accepted by electron carriers and release energy as they move along the electron transport
This causes protons to be pumped from the stroma to the thylakoid space.
As the membrane is impermeable to the protons a proton gradient builds across the membrane.
Protons diffuse through the channels in ATP synthase.…read more

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Source of carbon and oxygen for the production of large organic molecules, used to make structures and
act as energy stores and sources.
Limiting Factors
Limiting factor: is present at the lowest or least favourable value.
Law of limiting factors: if a process is influences by more than one limiting factor, the law of limiting factors
states that the rate will be limited by the factor in the least favourable conditions.…read more

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Take small pieces of plant (Elodea) and ensure bubbles are emerging from the cut end. Insert this into the
tube in the photosynthometer.
2. Stand the test tube in a beaker or 20oC water and add a spatula of potassium/sodium hydrogen
3. Place a light source close to the beaker. Light intensity: 1/d2
4. Pull the syringe and measure the bubble of gas.
5. Move the light further away and repeat step 4.
6. Record your date and plot a graph.
7.…read more




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