Download Module 4: Genetics

Module 8:
Cell Respiration and
Photosynthesis
(Option C for SL only)
8.2 Photosynthesis
8.2.1 Draw and label a diagram showing the structure of
a chloroplast as seen in electron micrographs.
Need to include: thylakoid membrane/grana, double outer
membrane, ribosomes, circular DNA, lipid globules, starch
granules, stroma
8.2.2 State that photosynthesis consists of lightdependent and light- independent reactions.
8.2.3 Explain the light-dependent reactions.
8.2.4 Explain photophosphorylation in terms of
chemiosmosis.
8.2.3 Explain the light-dependent reactions.
Outline the light-dependent reactions [6 marks]
• Chlorophyll in PSII/PS680 absorbs photons
• This produces an excited electron (photoactivation)
• Electron is passed down an electron transport chain from
one carrier to the next
• The electron from PSII provides an electron for PSI after
light absorption
• Absorption of photon causes photolysis where water is
broken down into oxygen and H+
• This is called non-cyclic photophosphorylation
• ATP is made via chemiosmosis using ATP synthase by
pumping H+ from they thylakoid space back into the
stroma
8.2.5 Explain the light-independent reactions.
Stroma
8.2.6 Explain the relationship between the
structure of the chloroplast and its function.
 Large surface area for light
absorption
 Small space inside
thylakoids for accumulation
of protons
 Fluid stroma for enzymes in
the Calvin Cycle
Summary of photosynthesis
8.2.7 Explain the
relationship between
the action spectrum
and the absorption
spectrum of
photosynthetic
pigments in green
plants.
What are the two
correlations we can
see when looking
at the two graphs?
8.2.8 Explain the concept of limiting factors in photosynthesis, with
reference to light intensity, temperature and concentration of
carbon dioxide.
• Affects light-dependent
reactions
• Low intensity: low ATP and
NADPH + H+ made
• This limits rate of Calvin Cyle
• Affects light-independent
reactions/Calvin Cycle
• Temperature affects enzyme
activity
• Less active at low temperatures
and fastest at high
temperatures until it denatures
Explain how triose phosphate is produced and
used in the chloroplasts of a plant [5 marks’
How is triose phosphate produced and
used in chloroplasts? [5 marks]
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RuBP and CO2 react together
This is called carbon fixation in the light-independent reactions
The reaction is catalysed by Rubisco
GP (glycerate-3-phosphate) produced
GP is reduced to form triose phosphate
Using NADPH and ATP
from light dependent reactions
Some triose phosphate is used to regenerate RuBP
Some triose phosphate is used to generate glucose/starch