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Energy
All organisms require energy to grow,
reproduce, move and carry out maintenance
and repairs.
Lightning
(electrical energy)
Energy can not be created or destroyed, but
it can be converted from one form to another.
The ultimate source of energy is the sun.
The Sun is the ultimate energy
source for life on Earth
Photo credit: NASA
Heat (thermal energy)
Energy Producers
Organisms which produce their own
energy are autotrophs.
Most plants are autotrophs.
Energy Consumers
Heterotrophs are organisms which cannot
make their own energy. All animals, fungi and
some bacteria are heterotrophs.
Photosynthesis
Photosynthesis is the action of transforming sunlight energy into
chemical energy. It produces:
Sugar (fuel)
oxygen
Water and nutrients
Sugar
Sunlight
Carbon dioxide
Oxygen gas
6CO2 + 12H2O
Light
Chlorophyll
C6H12O6 + 6O2 + 6H2O
Photosynthesis
Takes place in organelles called chloroplasts.
Chloroplasts are filled with a green pigment
called chlorophyll.
The Chloroplast
Grana, are stacks of
thylakoid membranes
containing chlorophyll
Stroma, the liquid
interior of the chloroplast
Inner
membrane
Thylakoid
sac (disc)
Outer
membrane
Photosynthesis
There are two phases in photosynthesis:
The light dependent phase
(D), which occurs in the thylakoid.
The light independent phase
(I), which occurs in the stroma.
D
I
D
I
Photosynthesis
Water
ATP
NADPH + H+
Water
Oxygen
Carbon dioxide
Sugar
Light Reactions of
Photosynthesis
Light Independent Phase
CO2
Calvin cycle (carbon
fixation) occurs in the stroma
of the chloroplast.
Carbon from CO2 is
incorporated into existing
organic molecules.
RuBisCo
G3P
RuBP
ADP +
Pi
ATP
NADPH
+ H+
ATP
Ribulose phosphate
ADP +
Pi
NADP
Triose phosphate
sugars
Factors Affecting
Photosynthetic Rate
the amount of light available.
the level of carbon dioxide (CO2).
the temperature.