Definition its apparatus essential factors

1. Photosynthesis-
Apparatus
Factors essential for
Photosynthesis
By:
SANTOSHKORAV
2017A7D

2. What is Photosynthesis ?
• Photosynthesis is often considered to be the
single most important life process on Earth.
• It changes light energy into chemical energy
and also releases oxygen.
• Without photosynthesis, there would be no
oxygen in the atmosphere.

3. Photosynthesis
Carbon dioxide + water glucose + oxygen
sunlight
absorbed by chlorophyll
6CO2 + 6H2O + energy  C6H12O6 + 6O2

4. Why is Photosynthesis important?
Makes organic molecules (glucose) out of
inorganic materials (carbon dioxide and
water).
• provide raw materials for building (timber,
• Furniture)
It begins all food chains/webs. Thus all life is
supported by this process.
It also makes oxygen gas!!

5. Where it Occurs ?
small green ovals are
chloroplasts
sizes (4-6 μm in diameter)
chloroplast contains neat
stacks called grana
The grana consist of sac-like
membranes, known as
thylakoid membranes
membranes contain
photosystems
Which contains chlorophyll,
a green pigment

6. Stages of Photosynthesis Occurs
•Stage I is called the light reactions. This
stage uses water and changes light energy
from the sun into chemical energy stored
in ATP and NADPH (another energy-
carrying molecule).
•This stage also releases oxygen as a waste
product.
•Stage II is called the Calvin cycle. This
stage combines carbon from carbon
dioxide in the air and uses the chemical
energy in ATP and NADPH to make
glucose.

7. Steps of the Light Reactions
All stapes take place in the thylakoid membrane
Step 1: Units of sunlight, called photons, strike a molecule of
chlorophyll in Photosystem II of the thylakoid membrane.
• The light energy is absorbed by two electrons (2 e-) in the
chlorophyll molecule, giving them enough energy to leave the
molecule.
Step 2: At the same time, enzymes in the thylakoid membrane use
light energy to split apart a water molecule. This produces:
• 2 e-. These electrons replace the two electrons that were lost from
the chlorophyll molecule in Step 1.
• an atom of oxygen (O). This atom combines with another oxygen
atom to produce a molecule of oxygen gas (O2), which is released
as a waste product.
• 2 H+. The hydrogen ions, which are positively charged, are
released inside the membrane in the thylakoid interior space.

8. Cont..
Step 3: The two excited electrons from Step 1 contain high energy and
they are carried by a series of electron-transport molecules, which
make up an electron transport chain. The two electrons are passed
from molecule to molecule down the chain. As this happens, their
energy is captured and used to pump more H ions into the thylakoid
interior space.
Step 4: When the two electrons reach photosystem I, they are no longer
excited. Their energy has been captured and used, and they need
more energy. They get energy from light, which is absorbed by
chlorophyll in photosystem I. Then, the two re-energized electrons
pass down another electron transport chain.
Step 5: Enzymes in the thylakoid membrane transfer the newly re-
energized electrons to a compound called NADP+. Along with a H
ion, this produces the energy-carrying molecule NADPH. This
molecule is needed to make glucose in the Calvin cycle.

9. Cont..
Step 6: By now, there is a greater
concentration of hydrogen
ions—and positive charge—in
the thylakoid interior space.
This deference in concentration
and charge creates what is
called a chemiosmotic gradient.
It causes hydrogen ions to flow
back across the thylakoid
membrane to the stroma, where
their concentration is lower.
•The H ions have energy as they flow down the chemiosmotic gradient.
The enzyme ATP synthase acts as a channel protein and helps the ions
cross the membrane.
•ATP synthase also uses their energy to add a phosphate group (Pi) to a
molecule of ADP, producing a molecule of ATP.
•The energy in ATP is needed for the Calvin cycle.

10. Photosynthesis Stage II: The Calvin Cycle
• Photosynthesis takes place in the Stroma surrounding the
thylakoid membranes of the chloroplast.
• The reactions of this stage can occur without light, so they
are sometimes called dark reactions.
• This stage of photosynthesis is also known as the Calvin
cycle because its reactions were discovered by a scientist
named Melvin Calvin. He won a Nobel Prize in 1961 for
this important discovery.
• In the Calvin cycle, chemical energy in NADPH and ATP from
the light reactions is used to make glucose.

11. Steps of the Calvin Cycle
The Calvin cycle has three major steps:
1. carbon fixation
2. reduction,
3. Regeneration
All three steps take place in the stroma of a chloroplast
Step 1: Carbon Fixation. Carbon dioxide from the atmosphere combines
with a simple, five-carbon compound called RuBP. This reaction
occurs with the help of an enzyme named RuBisCo and produces
molecules known as 3PG (a three-carbon compound, 3-
Phosphoglyceric acid).
Step 2: Reduction. Molecules of 3PG (from Step 1) gain energy from ATP
and NADPH (from the light reactions) and re-arrange themselves to
form G3P (glycerate 3-phosphate). This molecule also has three
carbon atoms, but it has more energy than 3PG. One of the G3P
molecules goes on to form glucose, while the rest o f the G3P
molecules go on to Step 3.

12. Cont…
Step 3: Regeneration.
The remaining G3P
molecules use energy
from ATP to form RuBP,
the five-carbon
molecule that started
the Calvin cycle. This
allows the cycle to
repeat.

13. Essential Factors
• Light
• Light is essential for photosynthesis. The sun is the main source of
light energy. Both quality and intensity of light are important for
photosynthesis. •
(a) Light Quality: The light consists of rays of different wavelengths.
Only red and blue light are effective for photosynthesis. Green light is
reflected or transmitted. Therefore, it does not play role in
photosynthesis. Light of wavelength longer than 700 run is not
effective for photosynthesis for green plants.
(b)Light Intensity: Photosynthesis begins at very low intensity. It
becomes maximum at bright daylight. But it decreases in strong light.
Different plants require different intensity of light. Most of light
reaching green leaves is reflected or transmitted. Thus only a small
part of light is absorbed. Thus only about 0.5 to 1.5% of light energy
is in photosynthesis.

14. Visible light is only
a small part of the
electromagnetic
spectrum (all forms
of light).

16. • Carbon dioxide
• The atmosphere is the chief source of carbon
dioxide. It contains only 0.03 % of the gas by
volume.
• The increase in the amount of carbon dioxide
increases the photosynthesis.
• This increase is more rapid up to I % of carbon
dioxide concentration. But it slows down beyond
this point.
• Higher concentrations have an inhibitory effect on
photosynthesis. It is clear that increase in
concentration of CO, increases the yield of plant

17. • Temperature
• A suitable temperature is necessary for photosynthesis. There are
three cardinals of temperature for photosynthesis.
(a) Minimum: It is minimum temperature at which the
photosynthesis starts. The plants of cold and temperate regions
have lower values of these cardinals.
• But tropical plants have higher stable of these cardinals.
Minimum temperature for many lichens (are composite organism
that arises from algae) is – 20°C. It is – 350 C for some conifers
(are perennial woody plants with secondary growth).
• Photosynthesis hardly starts at about 5°C in tropical plants.
Desert plants like cactus can carry on photosynthesis even at
55°C
(b)Optimum: Maximum photosynthesis occurs at that point The
optimum temperature also varies greatly.
• Photosynthesis increases with rise in temperature up to 25°C. This
increase follows Vant Hoffs law.
• According to this law the rate of chemical reaction doubles for
every rise of 10°C. This is true only if light or carbon dioxide is not
the limiting factors.

18. Cont…
(c) Maximum: It is the highest temperature at which
photosynthesis can take place.
• There is an initial increase in the rate of photosynthesis at this
temperature. But this is soon followed by a decline.
• Higher the temperature the more rapid is the decline. The
decline may be due to one or more of the following causes:
(i) Accumulation of the end products of photosynthesis.
(ii) Inhibitory effect of high temperature on the activity of
enzymes.
(iii)Failure of carbon dioxide to diffuse rapidly.

19. Thank You