Transcript The Calvin Cycle - mr-youssef-mci

Factors Affecting Photosynthesis
1.
light intensity, [CO2] and temperature
2.
C3 plant limitations
3.
C4 plants
4.
CAM plants
1.
increased [CO2] =
increased
photosynthesis
- up to a certain point until
enzyme active sites are
filled (photosynthetic rate
will plateau)
- due to increase in # of
reactant molecules in
Calvin Cycle
2.
increased
temperature =
increased
photosynthesis
- up to a certain point
until enzymes start to
denature causing the
photosynthetic rate to
decrease
- due to movement of
reactant molecules within
the Calvin Cycle
3. increased light
intensity = increased
photosynthesis


only to a certain plateau
after which an increase in
light intensity results in no
increase in the rate of
photosynthesis
This is because the
Calvin cycle cannot keep
up with the light reactions
Photosynthesis Rate
CO2 + H2O
light
C6H12O6 + O2

The overall rate of carbon fixation varies with
temperature, not with the intensity of light

Light reactions are affected by changes in
light intensity, not by significant changes in
temperature.



C3 plants undergo
photosynthesis as
described
stomata are open
during the day /
closed at night
What happens to
stomata in hot, arid
conditions?

In hot, arid conditions,
plants close the
stomata to prevent
water loss


increasing [O2] within the
cells
At high [O2], rubisco
binds to O2 rather than
CO2 in the process of
photorespiration

causes the plant to skip
the Calvin cycle.
Glucose is not produced.

adaptation to hot, arid environments
e.g. corn, sugarcane, grasses
C4 plants have a special mesophyll cell & bundlesheath cell structure.
1.
Mesophyll cells create 4-carbon molecules using
PEP carboxylase and release CO2 into the
bundle-sheath cells.
Bundle-sheath cells only perform the Calvin
cycle.
In hot, arid conditions, C4 cells provide enough
CO2 to ensure rubisco does not bind to O2
molecules.
2.

adaptation to hot, arid environments

e.g. cactus, pineapples (water storing plants)

Stomata are closed in the day and open at
night.
Pineapple
Sugarcane
C4
Mesophyll Cell
Organic acid
Bundlesheath cell
(a) Spatial separation of
steps. In C4 plants,
carbon fixation and the
Calvin cycle occur in
different
types of cells.
CALVIN
CYCLE
Sugar
CAM
CO2
1 CO2 incorporated
into four-carbon
organic acids
(carbon fixation)
2 Organic acids
release CO2 to
Calvin cycle
CO2
Organic acid
Night
Day
CALVIN
CYCLE
Sugar
(b) Temporal separation of
steps. In CAM plants,
carbon fixation and the
Calvin cycle occur in the
same cells
at different times.
1.
NIGHT: CO2 collected & incorporated into
organic molecules
2.
DAY: CO2 released from the organic
molecules where ATP & NADPH is produced
to allow the Calvin cycle to proceed
http://www.youtube.com/watch?v=Dq38MpYOb8w
HOMEWORK:
- Pg. 166 #9-12
- Pg. 172 #3, 4, 6
- Pg. 178 #1, 2, 6, 8 (a,b)