Autotrophs are organisms that use light energy or chemical energy and inorganic molecules to synthesise complex organic molecules.
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Define heterotrophs
Heterotrophs are organisms that ingest and digest complex organic molecules, releasing the chemical potential energy stored in them.
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How are chloroplasts adapted for their role?
The inner membrane with it's transport proteins can control entry and exit of substances between the cytoplasm and the stroma inside the chloroplast. The many grana provide a large surface area for the photosynthetic pigments, electron carriers and
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What are photosynthetic pigments?
Molecules that absorb light energy. Found in the thylakoid membranes, in photosystems. Each pigment absorbs energy associated with light of a specific wavelength.
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What is a photosystem?
A group of photosynthetic pigments in the thylakoid membrane. Consists of a primary reaction centre and accessory pigments.
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What is a primary pigment reaction centre?
The primary photosynthetic pigments in a photosystem act as reaction centres.
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What causes photosynthetic pigments to have a colour?
The light wavelengths they are reflecting.
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What are the two forms of chlorophyll a, what colour do they appear, and what light do they absorb?
P680, P700. Both appear yellow-green. They both absorb red light at different wavelengths. Chlorophyll a also absorbs blue light at a wavelength of 450nm.
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Where is P680 found and what is its peak of absorption?
Found in photosystem II and its peak of absorption is light at a wavelength of 680nm.
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Where is P700 found and what is its peak of absorption?
found in photosystem I and its peak of absorption is light at a wavelength of 700nm.
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What wavelengths of light does chlorophyll b absorb and what colour does it appear?
500nm and 640nm. It appears blue-green.
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What light do carotenoids reflect and what light do they absorb?
They reflect yellow and orange light. They absorb blue light.
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What are the main carotenoid pigments?
Carotene (orange) and xanthophyll (yellow)
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What does the molecular structure of cholorphyll consist of?
A long phytol (hydrocarbon) chain and a prophyrin group (contains a magnesium atom).
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What is the roll of carotenoids?
The don't contain a porphyrin group and aren't directly involved in the light-dependent reaction. They absorb light wavelengths that aren't well absorbed by chlorophylls and pass the energy to chlorophyll a at the base of the photosystem.
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What is photolysis?
An enzyme catalysed reaction where water molecules are split, using light energy.
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When does photolysis occur?
In photosystem II, during the light-dependent stage of photosynthesis.
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What is the equation for photolysis?
2H2O --> 4H+ + 4e- + O2
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What happens to the oxygen produced during photolysis?
Some is used by the plant for aerobic respiration but much of it diffuses out of the leaves, through stomata, into the air.
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What are the hydrogen ions produced by photolysis used for?
They are used in chemiosmosis to produce ATP. These protons are then accepted by NADP which becomes reduced NADP to be used during the light-independent stage to reduce carbon dioxide and produce organic molecules.
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What are the electrons produced by photolysis used for?
They replace those lost by the oxidised chlorophyll.
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What is photophosphorylation?
The formation of ATP for ADP and Pi in the presence of light energy.
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What are electron carriers?
Molecules that transfer electrons.
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What are electron acceptors?
Chemicals that accept electrons from another compound. They are reduced while acting as oxidising agents.
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Outline photophosphorylation.
1. When a photon hits a chlorophyll molecule the energy of the photon is transferred to two electrons and they become excited.
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Outline cyclic photophosphorylation.
Only uses PSI. The excited electrons pass to and electron acceptor and back to the cholorphyll molecule from which they were loss. Only small amounts of ATP is produced. This may be used in photosynthesis or in guard cells to bring in potassium ions.
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Outline non-cyclic photophosphorylation.
Involves both PSI and PSII. 1.Light strikes PSII, exciting a pair of electrons that leave the cholorphyll molecule from the primary pigment reaction centre.
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Other cards in this set
Card 2
Front
Define heterotrophs
Back
Heterotrophs are organisms that ingest and digest complex organic molecules, releasing the chemical potential energy stored in them.
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