The process which most living organisms obtain energy
PHOTOSYNTHESIS
QUESTIONS TO ANSWER
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1. What are the chemical reactants in photosynthesis?
2. Write the equation for photosynthesis.
3. What is the function of chlorophyll?
4. Describe the difference between the two photosystems.
5. What are the end products of the light dependent
reaction?
6. What are the end products of the light independent
reaction?
7. What is ATP and why is it important?
8. Where does photosynthesis occur?
9. Describe what happens in the 3 main stages of
photosynthesis.
10. What type of plants are C4 plants? CAM Plants?
BIOCHEMICAL PATHWAYS
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Series of chemical reactions where products are
the reactants in the next step
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
WHERE?
WHERE DOES ENERGY COME FROM?
Autotrophs make their own food from
photosynthesis
 Heterotrophs consume other heterotrophs or
autotrophs: ultimately the energy comes from
cellular respiration (opposite chemical reaction
of photosynthesis)
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OVERVIEW OF PHOTOSYNTHESIS
LIGHT REACTIONS
Occur in chloroplasts
 White light hits, absorbs red light and
chlorophyll b soaks up purple, blue and some
of the orange light. Green light is reflected so
that’s what we see.
 Chlorophyll a is the main player
 Chlorophyll b and carotenoids are accessory
pigments which allow more light to be used.
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PHOTOSYSTEMS
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Next the light energy is converted to
chemical energy through Photosystem
I and Photosystem II.
GLOSSARY
NADP: nicotinamide adenine dinucleotide
phosphate
 RuBP: ribulose biphosphate
 G3P: glyceraldehyde -3- phosphate
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PHOTOSYSTEM II
Light has enters and excites the electrons, they
leave the chlorophyll a to enter the “primary
electron acceptor”
 The primary e- acceptor moves electrons and
this loss of energy will push protons into the
thylakoid.
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CHEMIOSMOSIS
the buildup of protons from the thylakoid
space (from ETC of PII) gives us potential
energy, ATP synthase (enzyme) adds a
phosphate group (P) to ADP to make ATP
 NADPH and ATP fuel the next part:
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 The
Calvin Cycle
THE CALVIN CYCLE
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Carbon fixation, where a 3-carbon sugar is
produced from CO2, occurs in stroma.
See p120
ALTERNATIVE PATHS TO CARBON FIXATION
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C4 pathway- allow
carbon dioxide to be
fixed into four carbon
sugars
CAM pathway- some
plants are dedicated
CAM plants and others
can shift if environment
is unsuitable for other
pathways.
DISCUSS…
Could plants live without animals? Could
animals live without plants? Why or Why not?
 What causes leaves to change different colors
in the fall?
 What are the two stages of photosynthesis?
What happens in them and where?
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