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PHOTOSYNTHESIS
PHOTOSYNTHESIS
• The process by which
organic compounds are
synthesized from
inorganic compounds in
the presence of light in
autotrophic organisms
• Light energy is converted
into chemical energy of
organic molecules
• Sunlight is a form of
energy known as
radiation
• Radiation travels in
waves called
wavelengths
• Sunlight is a mixture of
all the visible
wavelengths (white light)
When visible light waves encounter
something they either pass through, are
reflected, refracted or are absorbed
• When white light is passed
through a prism, the light
rays of different
wavelengths spread out to
form a spectrum (they are
refracted)
• A pigment is a substance
that absorbs light
• The colors of an object
that you see depend on
which colors are
reflected or absorbed
• Ex - if you see red, all of
the wavelengths except
red are being absorbed,
and red is being
reflected
• If the wavelengths are
reflected equally an
object appears white
• If an object absorbs all
wavelengths it will
appear black
• What is being reflected
and absorbed if you are
looking at a banana?
• It will reflect yellow and
absorb all the other
colors
• Chlorophyll is a pigment in
plants that absorbs sunlight
• What color in plants is
being reflected?
• (green)
• The blue and red
wavelengths of light are
the best for photosynthesis
• Chromatography is a
technique used to
separate pigments in
plants
IMPORTANCE OF PHOTOSYNTHESIS
• Most of the chemical
energy available to
living organisms results
from photosynthesis
• Most of the oxygen in our
atmosphere comes from
photosynthesis
WORD EQUATION FOR
PHOTOSYNTHESIS
THE FORMULA EQUATION
CHLOROPHYLL
12 H20 + 6CO2--------C6H12O6+6O2+6H20
SUNLIGHT
PHOTOSYNTHESIS FACTS
• The reactants are carbon
dioxide and water
• Energy for the reaction is
supplied by sunlight
• Chlorophyll “traps” the
sunlight
PHOTOSYNTHESIS FACTS
• The products with the
stored energy is the
glucose
• The other products are
water and oxygen
• Water is both a product
and reactant
• Glucose is stored as
starch, used for
respiration or is used to
synthesize new
compounds
ATP
• ATP (adenosine
triphosphate) is an
energy storage molecule.
• Energy stored in the
chemical bonds of ATP
molecule is the energy
source for almost all the
life processes
• Oxygen is a product. But does it come from the H2O or the CO2
?
• By using radioactive isotope oxygen 18, scientists found that the
oxygen came from the water molecule.
FACTORS THAT AFFECT THE RATE OF
PHOTOSYNTHESIS
• Temperature
• Carbon Dioxide
Concentration
• Amount of Light
PHOTOSYNTHESIS REACTIONS
• The Light Reaction
(Photochemical Reaction)
• Occurs in the grana of the
chloroplasts
• The grana contain the
chlorophyll
• Requires light
• NADP is an enzyme that
transfers hydrogen
atoms from the light
reaction to the dark
reaction
DARK REACTION
• Is sometimes called carbon
fixation or calvin cycle
• It occurs in the stroma of
the chloroplasts
• PGAL is a 3 carbon
compound that is the actual
product of photosynthesis.
It can be converted to
glucose or other organic
compounds