Is the process by which plants
and certain other organisms
transform light energy into chemical
energy
What is their function?
light energy is captured and used to
convert water, carbon dioxide, and
minerals into oxygen and energy-rich
organic compounds.
Factors that Influence
of Photosynthesis
Light intensity and temperature
Carbon dioxide
Water
Minerals
Why is important?
Maintenance the life on Earth
If photosynthesis ceased,
there would soon be little
food or other organic matter
on Earth
Most organisms would disappear,
and in time Earth’s atmosphere
would become nearly devoid of
gaseous oxygen
History
The study of photosynthesis began in 1771 with
observations made by the English clergyman
and scientist Joseph Priestley
Priestley placed a sprig of mint plant in the container
until the air could no longer support combustion, in a
few days the mint had produced some substance (later
recognized as oxygen)
In 1779 the Dutch physician Jan Ingenhousz
expanded upon Priestley’s work
showing that the plant had to be exposed to light if
the combustible substance (i.e., oxygen) was to be
restored
In 1782 it was demonstrated that the
combustion-supporting gas (oxygen) was formed
at the expense of another gas, or “fixed air,” which
had been identified the year before as carbon
dioxide
in 1804 showed that the gain in weight of a plant
grown in a carefully weighed pot resulted from the
uptake of carbon, which came entirely from
absorbed carbon dioxide, and water taken up by
plant roots
In the 1930s Dutch biologist Cornelis van Niel
recognized that the utilization of carbon dioxide to
form organic compounds was similar in the two types
of photosynthetic organisms
The overall reaction
the “light” stage,
consisting of
photochemical recations
the “dark” stage,
comprising chemical
reactions controlled by
enzymes