Download Rate of Photosynthesis Geoff Klein April 11 As light intensity

Rate of Photosynthesis
Geoff Klein
April 11
As light intensity
increases, the rate
of photosynthesis
also increases until
a certain point. At
that point, the
light-saturation
point, the rate of
photosynthesis has
maxed out and can
not proceed any
faster. This is
because of other
limiting factors
like amount of CO2
available, the number of enzymes available and other
factors necessary for photosynthesis to occur. This
graph shows the rate of photosynthesis from the
affect of light by observing the amount of CO2
consumption. When there is no light, there is no
activity in the cell. What this causes is for CO2 to
actually leave the cell by diffusion. The intensity of
light has a direct effect on the rate of photosynthesis.
In terms of temperature, there is no significant
effect to photosynthesis as a whole, but temperature
does effect the Calvin cycle. As
temperature exceeds 30 degrees Celsius,
the Calvin cycle rate begins to decline
fast due to the denaturing of enzymes.
Between 10 and 30 degrees Celsius is the
optimal temperature for maximum
efficiency.
The higher the oxygen
concentration, the slow photosynthesis becomes. As oxygen levels increase,
competition for rubisco increases because both oxygen and carbon dioxide can react
with the active site. When CO2 binds, it becomes fixed into organic molecules
through the Calvin cycle. When O2 is bound, photorespiration occurs and
photosynthesis is reduced in activity.
Photorespiration occurs when there is more oxygen than carbon dioxide in
the cell. The oxygen is bound to rubisco creating glycolate then carbon dioxide. The
reason rubisco can react with two different substrates is because the early
prehistoric atmosphere consisted of mostly carbon dioxide. When the atmosphere
started to change to mostly oxygen, the function for reacting with oxygen was
created through evolution.
Net CO2 uptake =
Photosynthetic CO2 uptake – photorespiratory CO2 evolution – respiratory CO2
evolution
Net O2 evolution =
Photosynthetic O2 evolution – photorespiratory O2 uptake – respiratory O2 uptake
Cellular respiration
ATP
Photosynthesis
- ATP is used in energy investment
- Used to make final product,
phase of glycolysis
G3P
- Produced through cellular respiration
- Produced in noncyclic and
cyclic electron flow
NAD+/
- 2 NAD+ used in glycolysis/ pyruvate
- Used in stage 2 (non-cyclic
NADP+
oxidation, and 6 used in Krebs cycle
electron flow) when NADPH
reductase reduces it to go to
Calvin cycle
- Produced in Calvin cycle
CO2
- Produced in cellular respiration
- Used in photosynthesis
Glucose
- Used in cellular respiration
- Produced by photosynthesis
as a result of G3P
H+
H2O
- Pumped out into inter-membrane
- Pumped into thylakoid
space to produce ATP
lumen to create ATP
- Produced in glycolysis and ETC
- Used in photosynthesis
Review Questions
Q:
What effect does increasing light intensity have on photosynthesis?
A:
It causes the rate of photosynthesis to increase until the light-saturation
point.
Q:
How does the increase of oxygen concentration effect photosynthesis?
A:
As oxygen concentration increases, the rate of photosynthesis decreases.