Photosynthesis is the process by which plants, algae, and some bacteria use sunlight, water and carbon dioxide to produce oxygen and energy in the form of glucose. Chlorophyll in the leaves absorbs sunlight which is converted to chemical energy through a series of reactions. Oxygen is released as a byproduct. Glucose is temporarily stored as starch in leaves and is later transported and stored in other plant tissues like fruits and roots. The starch can be tested for using iodine, which turns blue or dark purple in the presence of starch. Sunlight, water, carbon dioxide and chlorophyll are essential for photosynthesis. Human dependence on fossil fuels has increased carbon dioxide levels, trapping heat and warming the planet.

1. Plants turn solar energy into food.
Therefore, it is called autotrophic
mode of nutrition
When animals eat plants and other animals,
that original solar energy is passed along
the food chain.
Living organisms depend on that food
directly or indirectly for their existence Are
called Heterotrophs
Photosynthesis

2. Photosynthesisis carried out by:
plants
cyanobacteria
certain bacteria
most algae phytoplankton
These organisms are known
as photoautotrophs or
producers meaning they
make their own food and
energy from the sun.
Consumers such as herbivores and
carnivores depend on the products
of photosynthesis that producers
make to live.

3. The photosynthesis reaction:
6 CO2 + 6 H2O + sunlight → C6H12O6 + 6 O2
6 Carbon
dioxide
molecules
6 Water
molecules
1 Sugar
(glucose)
molecule
6 Oxygen
molecules
Photosynthesis has 3 major events:
1. Sunlight is converted into chemical energy
2. Water (H2O) is split into oxygen (O2)
3. Carbon dioxide (CO2) is fixed into sugars (C6H12O6)
Photosynthesis is the process that converts solar energy
into chemical energy that is used by biological systems (

4. Utilizing the energy from sunlight, the cells containing
chlorophyll in green plants synthesize food using carbon
dioxide and water as raw materials. This process is called
photosynthesis

5. 2.1 Factors that affect photosynthesis
1.Sun light
2.water - *Terrestrial plants obtain water from soil for
photosynthesis.
*Water in the soil is absorbed through root hairs by
osmosis.
*The absorbed water then travels into root xylem through
cortex and endodermis.
*From there water is transported into mesophyll cells of
leaves via the xylem of stem and the veins of leaves.
*The network of veins in the leaves distributes water
throughout the leaf

6. 3.carbondioxide.
CO2 is obtained from the atmosphere for
photosynthesis.
CO 2 diffuses into leaf through stomata. Then it reaches
the mesophyll cells via inter cellular spaces.
4.Chlorophyll-special green pigment called chlorophyll
found in the chloroplasts in plant cells, absorb energy
from sunlight.
Activity 2.1
https://www.youtube.com/watch?v=BB5rvjZzg
FU&t=28s

7. 2.2 Products of photosynthesis
• The glucose (C6 H12O6 ) produced during
photosynthesis will be temporarily stored
as starch in leaves.
• Later, part of that starch is converted into sucrose
(C12H22O11)and transport into other tissues, via
phloem.
• The sucrose that is transported to storing organs are
again stored as starch.
E.g :-- Fruits, Vegetables, Yams, Leaves, Roots
• The by-product of photosynthesis is O2 and it is
diffused into the atmosphere through stomata.

10. Plants absorb red and blue light of sunlight during
photosynthesis
As glucose produced during photosynthesis is stored
temporarily as starch in leaves, it could be tested
whether the photosynthesis has taken place or not by
doing a test for starch.

18. Starch Test
https://www.youtube.com/watch?v=_rCjKTgAxgE

21. • As chlorophyll dissolve in alcohol the
leaf is boiled in an alcohol solution.
• Then the solution becomes green in
colour and leaf turns to pale colour.
• As alcohol is highly inflammable, it is
boiled in a water bath.
• If the leaf turns to blue or dark purple,
once Iodine is added, we can conclude
that starch is present in the leaf.

22. Observation
The leaf turns to blue or
dark purple, once Iodine is
added, we can conclude that
starch is present in the leaf
Conclusion
starch is present in the
leaf

24. Experiment to show that sunlight is required
for photosynthesis
https://www.youtube.com/watch?v=Yqo6-qDQoMA

25. There is no colour change in the covered
area of the leaf
The covered area of leaf turns to purple or blue
Conclusion
photosynthesis has taken place and
showed a colour change to dark
purple or blue indicating starch has
been produced.

27. https://www.youtube.com/watch?v=lji6Zx3_E30

33. https://www.youtube.com/watch?v=hhdvwmuwoAY

35. The white colour regions lack
chlorophyll, so photosynthesis has not
taken place.
Therefore starch has not been produced.
So it can be concluded that chlorophyll
is
essential for photosynthesis

36. Note
An experiment cannot be designed in the
laboratory to test the need of water for
photosynthesis
Reason -without water, the plant in the
control experiment will die.
Scientists have shown the need of water
for photosynthesis using water with 18 O 8
isotope.

37. Materials required :-
Beaker, boiling tube, glass funnel, aquatic plant
(Hydrilla, Vallisneria)

44. Human’s excessive dependence on fossil
fuels has led to an increase in the level
of CO2, a green house gas that traps heat
in the atmosphere and heats up the
earth. The rate at which human’s are
burning fossil fuels is too high for plants
and oceans to take carbon out of the
atmosphere.
When plantsabsorb carbon dioxidefrom the air, they
are removing carbon from the atmosphere and fixing
carbon into forms usable by other organisms. The
burning of fossil fuels for energy, releases carbon
dioxidegas intothe atmosphere increasing the
amount of carbon in the atmosphere.
Deforestation is a contributingfactor to the excessive
amountsof CO2 in the atmosphere and is also due to
human influence. With the destruction of entire
forests every day, we reduce the number of plants
availableto reduce carbon in the atmosphere.

45. Go Out and Thank a Tree!