SBI 4U
DATE: ______________________
OVERVIEW OF PHOTOSYNTHESIS
INTRODUCTION:
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metabolic process occurring in green plants, algae, some protists and cyanobacteria
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Photosynthesis is an ______________ PROCESS (building organic molecules which store
radiant energy as chemical potential energy)
-
Recall: Cellular Respiration is a _______________ PROCESS
Summary Reaction for Photosynthesis:
CO2:
-
used in light__________________ reactions (sometimes called ________ reactions)
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enters through stomata and goes to mesophyll cells
H2O:
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used in light____________________ reactions (sometimes called ________ reactions)
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enters through veins of leaf and goes to mesophyll cells
chlorophyll:
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light absorbing ___________ coloured pigment that begins the process of photosynthesis
-
found in _______________
-
primary function: convert ___________ energy into ___________ and __________ in order to
be used to convert __________ to ___________ molecules
Note: if any of the raw materials is absent, photosynthesis will NOT occur
Chloroplast
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organelle involved in photosynthesis
-
contains its own:
-
(a) ________________________
-
(b) ________________________
You should be able to:
- label a diagram of a chloroplast
- explain the structure/function of the chloroplast
OVERVIEW OF PHOTOSYNTHESIS
Photosynthesis consists of two complex series of events;
(1)
__________________________________
(2)
__________________________________
Light Dependent Reactions
- capturing light energy
-
occur within the __________ membrane of the chloroplast
-
produces:
(1) ______________________
(2) ______________________
(nicotinamide adenine dinucleotide phosphate, a coenzyme; similar to NADH)
Light Independent Reactions OR _____________________________________________________
- occur in either the presence or absence of __________
-
occur within the ______________ of the chloroplast
-
uses ATP and NADPH from the light reactions to form organic molecules like glucose, from CO2
-
produces:
(1) ______________________
(2) ______________________
-
completely enzyme catalyzed
LIGHT
- Electromagnetic (EM) radiation
-
o
Travels in wave packets called ____________
o
Photons with short wavelength = ________________
o
Photons with large wavelength = ___________________
Light is a mix of photons of different energies
o
Most of it we can’t see

o
If passed through spectroscope, photons can separate from one another
Called Electromagnetic Spectrum
Light – Photosystems (briefly)
-
Photosystems
o
Clusters of photosynthetic pigments embedded in thylakoid membrane
o
They absorb photons of particular wavelengths
o
Through light reactions they convert ADP to ATP and NADP+ to NADPH

Occurs in the stroma
PHOTOSYNTHETIC PIGMENTS
Chlorophyll
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found within _________________
-
___________ pigments
-
contain:
-
(1) _____________________________
-
(2) _____________________________
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chlorophyll a: absorbs _______________ and _____________ wavelength photons (reaction
centre of a photosystem)
-
chlorophyll b: absorbs _______________ and _____________ wavelength photons
(accessory pigment)
Carotenoids
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_____________ and _____________ pigments (accessory pigments)
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absorb only in the ______________ end of the spectrum
-
Excess energy absorber to protect chlorophyll and dissipate it as heat
o
E.g. β-carotene from carrots
Photosynthetically Active Radiation
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Ideal wavelengths for photosynthesis
o
-
Ranges from __________________________________
Combination of chlorophyll a and b, and all of the other accessory pigments that “help out”
-
LIGHT DEPENDENT REACTIONS
PHOTOSYSTEMS
- consists of:
(1) _________________________________________________________
_________________________________________________________
(2) _________________________________________________________
_________________________________________________________
Location of Photosystems: __________________________________________
Photosystem I: ___________________________________________________
Photosystem II: __________________________________________________
There are two separate light powered systems in the membranes of the thylakoid disc:
(1) _____________________________________
(2) _____________________________________
Cyclic Photophosphorylation
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used by prokaryotes (eg bacterial photosynthesis)
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involves only ___________________ (PS I)
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PS I contains ______________
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chlorophyll a electrons return to chlorophyll a
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product = __________ (no NADPH is made)
Description:
(1)
PS I (P700) absorbs ___________ energy, causing the two ____________ to become
excited.
(2)
The two excited electrons enter an _______________________________.
(3)
The two excited electrons are captured by the protein _________________, causing some of
their energy to be lost.
(4)
The two excited electrons are then captured by the _____________________ protein
complex and lose more energy. At this point, enough energy has been lost to add a P to ADP
forming ________.
(5)
The passing of electrons from cytochrome b6-f complex to the next electron carrier,
___________________(Pc) results in further lowering of the energy in the electrons to almost
the ground state
(6)
The passing of the two electrons to ______ returns the electrons to both the
_______________ molecule and the __________ state.
Non-Cyclic Photophosphorylation
- used in photosynthesis of green plants
-
involves both ___________________ (PS I) and ___________________ (PS II)
-
chlorophyll a electrons are passed along to make ____________ and are replaced by
__________ electrons
Description:
(1)
PS II absorbs __________ energy causing two electrons of chlorophyll P680 to become
excited.
(2)
A Z protein, associated with PS II and facing the thylakoid _________, splits __________ into
____________, _____________ and ______________. Two __________ are used to
replace the excited electrons in chlorophyll P680. ___________ leaves the chloroplast as a
byproduct.
The _________ remain in the thylakoid space add to the proton gradient that powers
chemiosmosis.
(3)
The two excited __________ travel through a series of proteins within the
_______________________________.
(4)
As the two excited ____________ move from the excited reaction centre of PS II to
___________________(PQ), energy is lost.
(5)
This energy is used to move _________ protons from the _____________ to the
____________. This creates a proton gradient for chemiosmosis.
(6)
The increase in proton concentration within the thylakoid lumen drives protons out of the
lumen to the ________ via a special protein called _____________. This proton motive force
is used to produce ___________.
(7)
The electrons continue to move from PQ to other components of the electron transport chain
(cytochrome b6-f complex to Plastocyanin to PS I) eventually replacing the 2 electrons that
were lost by PS I when it was struck by photons.
(8)
The two excited electrons from PS I pass through another electron transport chain containing
the protein _________________(Fd).
(9)
The two excited electrons are then captured by ___________________, which uses the two
electrons and protons from the stroma to reduce ___________ to ___________.
(10)
The ____________ and ________ are used to drive light independent reactions.
LIGHT INDEPENDENT REACTIONS
Calvin Cycle
-
reactions that convert ________________ into _______________ molecules
-
occur in the ___________ of chloroplasts
Summarize the 3 phases listed below:
(1)
Carbon Fixation:
__________________________________________________________________________
__________________________________________________________________________
________________________________
(2)
Reduction Reactions:
__________________________________________________________________________
__________________________________________________________________________
________________________________
(3)
Regeneration of RuBP:
__________________________________________________________________________
__________________________________________________________________________
________________________________