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Powerpoint@lecture Slides Are Prepared By Biology Lecturer, KMPk

mailto:point@lecturemailto:point@lecture

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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