3. OBJECTIVES:
Give overall outline of photosynthetic process
that leads to the production of glucose
7.1: OVERVIEW OF PHOTOSYNTHESIS
4. Photosynthesis occurs in the chloroplasts.
Chloroplast contains chlorophyll.
Chlorophyll plays an important role in the
absorption of light energy during
photosynthesis.
An Overview of Photosynthesis
5. * in plants, algae, unicellular protists
(e.g. Euglena sp.) & photosynthetic
bacteria
The chemical process by which green plants
and other phototrophs synthesize organic
compounds (e.g. carbohydrates) from CO2 &
H2O in the presence of sunlight
(i.e. conversion of light energy to chemical
energy)
Definition of Photosynthesis
6. 6
6CO2 + 6H2O C6H12O6 + 6O2
Carbon
Dioxides
Water Glucose Oxygen
Light energy
Chlorophyll
Equation for Photosynthesis
In presence of light, green plants produced
organic compounds and oxygen from
carbon dioxide and water
6 CO2 + 6H2O + 18 ATP + 12 NADPH
C6H12O6 + 6O2 + 6H2O +18 ADP + 18 Pi + 12 NADP+
or
7. LIGHT
A form of energy called electromagnetic
energy @ electromagnetic radiation.
Most important radiation:
- Narrow band from about 380nm to 750nm
Known as visible light (can be detected as
various colors by human eyes)
Able to stimulate photosynthesis
8. LIGHT
Consist of photon
Fixed amount of energy in each photon
Amount of energy is inversely related to
wavelength of light
The shorter the wavelength, the greater the
energy of each photon.
10. CHLOROPLAST
Leaf: major site
of photosynthesis
Chloroplast:
Mainly in cells of
mesophyll
Mesophyll cell
has about 30 to
40 chloroplasts.
11. • Chloroplast found in mesophyll cell of leaf.
• Chloroplast has stroma and thylakoid which are
essential structure for photosynthesis.
Stroma :
Fluid filled matrix which contain enzyme for light
independent reaction in photosynthesis.
Thylakoid:
Associated with chlorophyll molecule forming
photosystem complexes involve in light dependent
reaction.
CHLOROPLAST
14. Why Are Plants Seen As Green?Why Are Plants Seen As Green?
Chlorophylls:
Absorb blue and
red light while
reflect green light
Blue and red light:
- Effectiveness
colors to
stimulate
photosynthesis
16. • Occur at thylakoid membrane
• Light energy is used to split (broke down) H2O into H and O2.
• Forming ATP and NADPH and O2 (by product) is given off
• Occur in stroma
• CO2 is built up into sugars using the products of the light
dependent stage.
• ATP and NADPH are used in this stage.
Light Dependent Reaction
Light Independent Reaction
Stage in Photosynthesis
18. Importance of Photosynthesis
• Produce the building blocks for complex compound
in plant such as starch, cellulose and lignin.
• Provide energy needed for chemical changes in the
form of ATP.
• Provide food to primary consumer.
• Help reduce excess carbon dioxide, CO2 and increase
oxygen, O2 concentration in the air.
20. Photosynthetic Pigment
• Photosynthetic pigment can
be found in thylakoid and
intergranal lamella.
• Function of this pigment:
To absorb the visible light.
• Photosynthesis pigments
are the substances that
absorb visible light (narrow
band between 380 to 750
nm).
• Each wavelength is different
coloured light.
21. Absorption Spectrum of Photosynthesis
• The efficiency of photosynthesis in different wave
length can be explained by considering the absorption
properties of the photosynthetic pigment.
22. Absorption Spectrum of Photosynthesis
• The absorption spectra of
pigment chlorophyll a and
chlorophyll b show that
absorption is highest in blue
(445 – 500 nm) and red (620 nm
– 740nm) light.
• The least is green (500 – 575
nm) light.
• Wave length that optimally
absorbed and used by green
plant as the source of energy
are in blue and red region.
23. Photosynthetic Pigment
• Thylakoid membrane have several types of
pigment :
Chlorophylls (the most important pigments)
Carotenoids (accessory pigments)
24. 24
Chlorophylls (absorb blue and red lights):
carotenoids (absorb purple lights):
Chlorophyll a Bluish green pigment
Chlorophyll b Yellowish green pigment
Xanthophyll Yellow pigment
Carotene Orange pigment
Phaeophytin Grey pigment
PHOTOSYNTHETIC PIGMENTS
25. Photosynthetic Pigment
Chlorophyll a Chlorophyll b
• Act as primary pigment • Act as accesory pigment
• Participate directly in light
dependent reaction
• Convert light energy to
chemical energy.
• Captured light and
transfer it to chlorophyll
a
• Then initiates the light
dependent reactions.
26. • The pigments are organised into photosystem
• Two types of photosystem:
1.Photosystem I
2.Photosystem II
• Each photosystem consists of a light-harvesting
system and reaction centre
Role of Photosynthetic Pigment in
Photosynthesis
28. A technique used to separate
photosynthetic pigments
CHROMATOGRAPHY
29. Graph plotting absorption of light by
photosynthetic pigments ( y-axis ) against
wavelength of light ( x-axis )
Graph plotting absorption of light by
photosynthetic pigments ( y-axis ) against
wavelength of light ( x-axis )
ABSORPTION SPECTRUM
30. Graph plotting rate of photosynthesis ( y-axis )
against wavelength of light ( x-axis )
Graph plotting rate of photosynthesis ( y-axis )
against wavelength of light ( x-axis )
Show effectiveness of different wavelengths in
stimulating photosynthesis
ACTION SPECTRUM
31. Consist of a
porphyrin ring
(with
magnesium at
the centre) &
hydrocarbon
chain
Consist of a
porphyrin ring
(with
magnesium at
the centre) &
hydrocarbon
chain
STRUCTURE OF CHLOROPHYLL
