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7/30/2019 Photosynthesis Hour 1
1/23
Powerpoint@lecture Slides Are Prepared By Biology Lecturer, KMPk
mailto:point@lecturemailto:point@lecture7/30/2019 Photosynthesis Hour 1
2/23
16.1 Overview of photosynthesis
16.2 Absorption spectrum of photosyntetic
pigments
16.3 Light dependent reaction
16.4 Light independent reaction
16.5 Alternative mechanisms of carbon fixation:
Hatch-Slack (C4) and Crassulacean Acid
Metabolism (CAM) pathways
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16.1 Overview of photosynthesis
16.2 Absorption spectrum of
photosyntetic pigments
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At the end of this topic, students should be
able to;
outline of photosynthetic process that leads to
the production of glucose
state the photosynthetic pigments involved in
photosynthesis
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What is PHOTOSYNTHESIS?
The conversion of light energy to chemical
energy that is stored in glucose or other organic
compounds.
(Campbell 8th edition)
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Photosynthesis
Begins with (reactants):
Sunlight (radiant energy)
Water (from the ground)
Carbon dioxide (from the air)
Ends with (products):
Oxygen
- Released to atmosphere
Glucose
- Stored chemical energy
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Chloroplast
Organelle where photosynthesis takes place.
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Photosynthesis as REDOX
REACTION
Water split into hydrogen and oxygen (Photolysis).
Electron are transferred along with hydrogen ions fromwaterto carbon dioxide.
Thus, reduce to sugar.
6 CO2
12 H2OReactants:
Products: C6H12O6 6 H2O 6 O2
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Photosynthesis
Photosynthesis reverses the direction of electron
flow.
- electrons increase in potential energy as
they move from water to sugar.
- thus, this process requires energy.
This energy boost is provided by light.
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The Stages of Photosynthesis
The anabolic pathway involves
TWO processes:
a. Light dependent reaction
(Light reaction)
- the photo part of photosynthesis
- thylakoid
b. Light independent reaction
(Calvin cycle)
- the synthesis part of
photosynthesis
- stroma
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Overview of Photosynthesis
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The Nature of Sunlight
Light is a form known as electromagnetic
energy, also called electromagnetic radiation.
Light travels in waves.
The distance between the crests of
electromagnetic waves is wavelength ( ).
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The Nature of Sunlight
Wavelength determines the type of electromagnetic energy.
- the amount of energy inversely related to the wavelength of light.
- the shorter the wavelength, the greater the energy of each
photon of that light.
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Why leaves are green?
The photosynthetic pigment (chloropyll) ofchloroplast absorb violet-blue and red light and
reflect green light.
But, what is photosynthetic pigments?
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Photosynthetic Pigments
Photosynthetic pigments as the light receptor.
Embedded in thylakoid membrane.
Different pigments absorb different wavelength oflight.
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Photosynthetic Pigments
TWO types of photosynthethic pigments:
- Main pigments
- Accessory pigments
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Chlorophyll as
Photosynthetic Pigments
Chlorophyll absorb red and
violet-blue light but reflect green
light.
Type of chlorophyll:
i. Chlorophyll a
- blue-green pigments
- main pigments
ii. Chlorophyll b- yellow-green pigments
- accessory pigments
iii. Chlorophyll c
- accessory pigments
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Yellow and Orange pigments
Type of Carotenoids:
i. beta carotene
ii. Xanthophylliii. Phaeophytin
Carotenoids as Accessory Pigments
- absorb violet and blue green light
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Absorption Spectrum of
Photosynthetic Pigments
Absorption spectrum
is a visual
representation ofhow well a particular
pigments absorbs
different wavelength
of visible light.
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16.3 Light dependent reaction
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