Photosynthesis
Light reaction
Dark reaction
Key components of the
Light Reaction
2 photosystems
2 electron transport chains
ATP synthase
Embedded in the _________
Which organelle? _________
The photosystems, 1 & 2
They are an array of _________molecules
What do these molecules do?
Hint:
• They absorb light energy
• And, the absorbed energy excites its
electrons to a higher energy level
Photosystem 1
Energized electrons are passed down
an ____________
What do these electrons end up doing?
Hint:
• They are added to NADP+ to form NADPH
Photosystem 2
Meanwhile energized electrons are
passed down another ____________
What do these electrons end up doing?H+
Hint:
• Their energy is used to pump H+
H+
From the __________ into the ___________ compartment
What does pumping H+ ions cause?
Hint:
Concentration gradient
Where do these electrons go? And, why?
Hint:
To photosystem 1
To replenish its lost electrons
How does this photosystem replenish its electrons?
Hint:
By splitting water
So, photosystem 1 is thought of as the:
Hint:
The NADPH producing photosystem
And, photosystem 2 is thought of as the:
Hint:
The water splitting photosystem
What is the ‘tally’ of energy production
so far?
Hint:
What about ATP?
Hint:
Remember the hydrogen ions?
The buildup of __________ inside the ___________
compartment stores __________ energy.
The potential energy is harvested by
what enzyme?
Hint:
ATP synthase
And, how is ATP made?
1
2
3
4
5
6
3
2
5
4
1
6
Next, the ‘sugarproducing’ Calvin cycle
The final look at
energy production
from the light
reaction:
NADPH
ATP
No sugar produced in the light reactions!
The Calvin cycle
What energy does the Calvin cycle use?
NADPH
Hint:
ATP
What else does the Calvin cycle need to
get started?
CO2
A quick rundown of the Calvin
cycle tells us that:
1. Carbon is used from _________
2. Energy is used from _________
3. High energy electrons are used from ______
4. The cycle itself produces an energy-rich
molecule called _________
5. The plant cell uses ______ as raw material
to make ________
Called a cycle because:
Regenerates the starting
material with each turn of the
cycle
What is the cycle?
A complex series of chemical reactions
Where does it occur?
In the stroma of the chloroplast
The cycle begins with:
• Input of CO2
(how many?)
What is the carbon
bound to?
• RuBP molecules
(how many?)
But, what happens to
RuBP?
• Its broken up into 3-PGA
RuBP: ribulose bisphosphate, a 5 carbon sugar
3-PGA: 3-phosphoglyceric acid, a 3 carbon compound
What is the next step?
Energy is required
To convert __________
to product __________
What happens to ATP,
NADPH?
G3P: glyceraldehyde 3-phosphate, a 3 carbon sugar
CO2
Half way around the
cycle…
RuBP
3 PGA
Does this diagram
represent one or
more turns of the
cycle?
G3P
What is the name of this
molecule?
What happens with one
full turn of the cycle?
CO2
Starting material _______ is
regenerated
3 PGA
G3P
How many molecules of
direct product are produced
at this point?
G3P
One complete cycle …
How many cycles to
make one glucose?
Depending on the needs of the plant,
what are some facts about G3P?
Some G3Ps are used to build glucose
Glucose can combine into starch
Or cellulose
Still other G3P’s form sucrose
Some sugar is broken down by
cellular respiration
Uses oxygen in the plant’s own mitochondria
Generates ATPs that powers other work of the plant
Excess oxygen diffuses out of the leaf
through the pores, while more CO2
enters
Learning check
1. The Calvin cycle must turn ______ times for
the plant to be able to produce a single
molecule of glucose.
2. What is the function of NADPH in the Calvin
cycle?
3. The Calvin cycle takes place in the ______.