This document discusses photosynthesis and its key stages and history. It notes that: - Photosynthesis is the process by which plants, algae and bacteria use sunlight to convert water, carbon dioxide and minerals into oxygen and glucose. - Energy from photosynthesis carried out by plants millions of years ago is responsible for fossil fuels after the remains of these organisms were deposited and slowly converted over geological time. - The light-dependent and light-independent stages of photosynthesis are described, including the locations and key reactions in each.

2. Presented by: Yasir Mueen Gishkori
2015-uam-177
PLANT PATHOLOGIST
MNS UNIVERSITY OF AGRICULTURE
MULTAN

3. Photosynthesis
From sunlight to glucose

4. Photosynthesis
• A process used by plants, algae and certain
bacteria to change energy from sunlight to
chemical energy
• Light energy is captured and used to convert
water, C02 and minerals to oxygen and
glucose
• Energy produced by photosynthesis carried
out by plants millions of years ago is
responsible for the fossil fuels

5. Photosynthesis
• In past ages, green plants and small organisms
that fed on plants increased faster than they
were consumed, and their remains were
deposited in Earth’s crust by sedimentation
and other geological processes
• These organic remains were slowly converted
to fossil fuels

6. Development of the idea
• In 1771, Joseph Priestley had burned a candle in a
closed container until the air within the container
could no longer support combustion.
• He then placed a sprig of mintplant in the
container
• After several days the mint had produced some
substance (later recognized as oxygen) that
enabled the confined air to again support
combustion

7. Development of the idea
• 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 was to be
restored
• He also demonstrated that this process
required the presence of the green tissues of
the plant.

8. Development of the idea
• 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
• Almost half a century passed before the concept
of chemical energy had developed sufficiently to
permit the discovery (in 1845) that light energy
from the sun is stored as chemical energy in
products formed during photosynthesis

9. PHOTOSYNTHESIS
1. Light dependent stage ( occurs on thylakoid
membranes)
2. light independent stage ( occurs in the
stroma of chloroplast)

11. Non cyclic photophosphorylation and
cyclic photophosphorylation

12. Light dependent stage
• Maximum no of ATP are produced in cyclic
photophosphorylation
• Photolysis is not needed for cyclic
photophosphorylation
• Oxygen is produced during light dependent
stage

13. Light independent stage
• ATP and NADPH produced in light reaction are
used in calvin cycle
• And carbon dioxide comes from outside
• The carbon dioxide molecules diffuse into the
cells through small holes in the underside of
the leaf. The first enzyme that picks them up is
called Rubisco.

14. Light independent stage
• Rubisco catalysis the connection of the small
molecule ribulose-1.5-bisphosphate
phosphate (RuBP) to carbon dioxide -
therefore fixing the inorganic CO2 as an
organic molecule
• RuBP contains 5 carbons as well as oxygen,
hydrogen and phosphate and it bonds to the
CO2 to create a 6 carbon molecule

15. Light independent stage
• This promptly splits into two small 3 carbon
molecules 3-phosphoglycerate
• It is then converted into G3P with the help of
reduction of ATP and NADPH
• 3 molecules of carbon dioxide produces 6
molecules of G3P
• G3P is actually the form of sugar that
produces in glycolysis