Photosynthesis

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  • Created by: Steff06
  • Created on: 01-02-16 14:00
What is photosynthesis?
The process where light energy from the sun is converted into chemical energy and used to synthesise large organic molecules from inorganic substances.
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Differences and Similarities between autotrophs and heterotrophs
Differences = ONLY autotrophs can synthesise complex organic molecules from simple inorganic ones and ONLY autotrophs use light energy. Similarities = They both can respire and can both hydrolyse complex organic molecules.
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What is a photosynthetic pigment?
A substance that absorbs some wavelengths of light, but not others. They are present in thylakoid membranes and arranged in photosystems. They are also used in the light dependent stage.
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Describe chlorophyll a
It is in the primary pigment reaction centre. It comes in 2 forms, P680 in photosystem 2 and P700 in photosystem 1. It appears yellow- green and absorbs red and blue light. It contains an Mg atom which excites electrons.
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Name and describe the accessory pigments
Chlorophyll b absorbs light at wavelengths between 500-640nm and appears blue-green. Carotenoids absorb blue light. They reflect yellow (xanthophyll) and orange (carotene) light.
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Differences between photosystem 1 and photosystem 2
Each contains a different combination of chlorophyll pigments. PS1 absorbs light at 700nm and PS2 absorbs light at 680nm. PS1 particles are found on the intergranal lamellae and PS2 particles are found on the grana.
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Name the different types of pigment involved in photosynthesis
Carotene, xanthophyll, phytophytin, chlorophyll a and chlorophyll b
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What part of the chloroplast can be considered the light harvesting part?
Photosystems
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What are the 2 different forms of chlorophyll a called and where do you find them?
P680 in photosystem 2 and P700 in photosystem 1.
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Where does the light INDEPENDENT stage of photosynthesis take place?
Stroma
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Where does the light DEPENDENT stage of photosynthesis take place?
Thylakoid membrane
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1st stage of the light dependent stage of photoynthesis
The light energy excited electrons in chlorophyll. The light energy is absorbed by chlorophyll in PSII which excites the electrons (Mg). The electrons move to a higher energy level, leave the chlorophyll molecule and are taken up by electron acceptor
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What is the energy released in the light dependent stage used for?
To drive the synthesis of ATP from ADP and Pi
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What is the primary electron acceptor associated with PSII
Plastaquinone
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2nd stage of light dependent stage
Photolysis of water produces protons, electrons and oxygen. The electrons must be replaced, done by splitting water.
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3rd stage of light dependent photosynthesis
Energy from excited electrons makes ATP. Electrons lose energy as move along ETC. Energy pumps protons to thylakoid space to create conc gradient.Protons move through ATP synthase, causes ADP+Pi to produce ATP (Chemiosmosis).
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Define chemiosmosis
The process where the movement of H+ ions across a membrane generates ATP.
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4th stage of light dependent photosynthesis
Generation of reduced NADP. Light energy absorbed by PSI, excites electrons to higher energy level. Taken up by ferrodoxin. Electrons combine with protons to produce reduced NADP.
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What is the primary electron acceptor for photosystem 1
Ferrodoxin
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Describe cyclic photophosphorylation
It only uses PSI. Cyclic, because electrons are recycled back to PSI via electron carriers. Only produces small amounts of ATP.
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Which photosystems are involved in cyclic and non-cyclic photophosphorylation
PSI in cyclic and PSI and PSII in non-cyclic.
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Where does PSII get its replacement electrons from in non-cyclic photophosphorylation?
Photolysis of water
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Where does PSI get its replacement electrons from in cyclic and non-cyclic photophosphorylation?
In cyclic the electron are recycled and in non-cyclic they get them from photosystem 2.
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What is the fate of electrons in cyclic and non-cyclic photophosphorylation?
The electrons in cyclic are recycled and the electrons in non-cyclic combine with protons to form reduced NADP.
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What are the required reactants for cyclic photophosphorylation?
ADP, Pi, light
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What are the required reactants for non-cyclic photophosphorylation?
ADP, Pi, light, NADP, water
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What are the products of cyclic photophosphorylation?
ATP
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What are the products of non-cyclic photophosphorylation?
ATP, oxygen, reduced NADP.
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Card 2

Front

Differences and Similarities between autotrophs and heterotrophs

Back

Differences = ONLY autotrophs can synthesise complex organic molecules from simple inorganic ones and ONLY autotrophs use light energy. Similarities = They both can respire and can both hydrolyse complex organic molecules.

Card 3

Front

What is a photosynthetic pigment?

Back

Preview of the front of card 3

Card 4

Front

Describe chlorophyll a

Back

Preview of the front of card 4

Card 5

Front

Name and describe the accessory pigments

Back

Preview of the front of card 5
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