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Photosynthesis ­
OCR A2 Biology…read more

Slide 2

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What is it?
· The process whereby light energy from the
Sun is converted to chemical energy.
· It is perhaps one of the most important
processes as nearly all life on Earth
depends on it.…read more

Slide 3

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Autotrophs and Hetrotrophs:
Autotrophs ­ uses simple inorganic
molecules to make its own food.
Photoautotrophs ­ uses light as the source
of energy
Chemoautotrophs ­ uses chemical energy
Hetrotrophs ­ gains its nutrients from
complex organic molecules and digests
them into simpler soluble molecules and
respires some to produce energy.…read more

Slide 4

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Chloroplasts ­ Adaptations:
· The inner membrane contains
transport proteins so can
control the substances that
enters/exits the stroma.
· The grana provide a large
surface area for photosynthetic
pigments, electron carriers and
ATP synthase enzymes
· The photosynthetic pigments
are arranged in photosystems
· The stroma contains enzymes
needed for the light-
independent stage.
· The grana are surrounded by
the stroma so products from
the light dependant stage can
pass into the stroma easily…read more

Slide 5

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Photosynthetic Pigments:
· They are substances that
absorb certain
wavelengths of light and
reflect others.
· Different pigments absorb
different wavelengths of
· They are found in the
thylakoid membrane,
arranged in funnel shaped
structures called
photosystems…read more

Slide 6

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Types of Pigment:
·Mixture of pigments all containing a phytol chain and a porphyrin
·2 forms of chlorophyll a ­ P680 and P700 ­ Both yellow/green and
found at the centre of photosystems ­ primary pigment reaction centre.
·Chlorophyll b absorbs light of wavelengths 500 and 640nm
Accessory Pigments:
·Carotenoids reflect yellow and orange light and absorb blue
·They do not contain the porphyrin group and are not directly involved
in the light dependant reaction
·They absorb the light that chlorophylls do not.
·Carotene and xanthophyll are the main carotenoid pigments.…read more

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