Introduction to Photosynthesis
• define the terms autotroph and heterotroph;
• state that light energy is used during
photosynthesis to produce complex organic
molecules;
• explain how respiration in plants and animals
depends upon the products of photosynthesis;
• state that in plants photosynthesis is a twostage process taking place in chloroplasts;
What is Photosynthesis?
• Light energy from the sun is transformed into
chemical energy and used to make organic
molecules (containing carbon) from inorganic
substances (no carbon)
• Nearly all life on earth depends on it
• Light energy turns into chemical potential energy
available to consumers and decomposers
• Releases oxygen, so aerobes depend on it for
respiration
Autotrophs and Heterotrophs
• Using Cambridge Biology 2 p65, define the
terms autotroph and heterotroph
Autotroph: organisms that use light energy or chemical energy and inorganic
molecules (carbon dioxide and water) to synthesis complex organic molecules
Chemoautotrophs are early prokaryotes that used exergonic (reactions that release
heat) to make complex organic molecules
Photoautotrophs use sunlight and inorganic molecules (carbon dioxide and water)
Heterotrophs: organisms that ingest and digest complex organic molecules
releasing the chemical potential energy stored in them e.g. humans
Does everything depend on
Photosynthesis?
• Task: Using Cambridge Biology 2 p65, explain
why respiration in autotrophs and
heterotrophs depends on photosynthesis (5)
Answer...
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Respiration requires oxygen
Oxygen is the final electron acceptor
In the electron transport chain
Photosynthesis produces oxygen
Both photoautotrophs and heterotrophs release
the chemical potential energy in complex organic
molecules
• Complex organic moloecules e.g. carbohydrates
made in plants during photosynthesis
The Chloroplast
• Photosynthesis takes place in specialised
organelles called chloroplasts within plant
cells
• The equation for photosynthesis is:
6CO2 + 6H20  C6H12O6 + 602
Looking at Chloroplasts
• explain, with the aid of diagrams and electron
micrographs, how the structure of
chloroplasts enables them to carry out their
functions;
• define the term photosynthetic pigment;
• explain the importance of photosynthetic
pigments in photosynthesis;
Task
• Using Cambridge Biology 2 p65–68, and OCR biology p60-61
outline how the structure of chloroplasts enables them to
carry out their functions
• This must be completed as a poster or information resource/
PowerPoint etc.
• You have 2 weeks to complete this task
Success Criteria
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Your Resource must include:
The structure of chloroplasts
How chloroplasts are adapted to their role
Photosynthetic pigments
Accessory pigments
Rf values: what they are and how they are
calculated