Photosynthesis

PHOTOSYNTHESIS 1. Define the term of photosynthesis. In autotrophic nutrition, organisms such as green plants and photosynthetic bacteria produce their own organic nutrients using simple organic raw materials and energy. If the energy used is light, mainly sunlight, the autotrophic process is known as photosynthesis. Photosynthesis is the synthesis of organic compounds from simple inorganic materials, namely carbon dioxide and water, in the presence of chlorophyll that absorbs the light energy required. The organic compounds synthesised are mainly carbohydrates, proteins and lipids. Photosynthesis is the chemical process by which plants and other photoautotroph synthesize organic compounds from CO2 and H2O in the presence of sunlight

Plant cells with visible chloroplasts.

In all green plants, photosynthesis occurs in cells with choloroplasts. The green pigment chlorophyll, located within the chloroplast, absorbs energy from sunlight. The light energy absorbed is then converted to chemical energy in organic compounds such as sugars, starch, amino acids and lipids, and oxygen is released as a by-product. These photosynthetic products have a higher energy content than that of the raw materials (CO2 and H2O). Photosynthesis is thus an endergonic process

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Chlorophyll plays an important role in the absorption of light energy during photosynthesis.

The leaf is the primary site of photosynthesis in plants.

Equation for Photosynthesis Light

6CO2 + 6H2O Carbon Dioxides

Water

Chloropl asts

C6H12O6 + 6O2 Glucose

the product of the process is sugar (Glucose) and O2

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Oxygen

The many biochemical reactions involved in photosynthesis can be divided into two phases, namely a) The light-dependent reaction, which occurs in the grana of chloroplasts and requires a continual supply of light, and b) The light-independent reaction, which occurs in the stroma of chloroplast and can carry on for some time in darkness after the light-dependent reaction. During the light dependent reaction, several intermediate compounds are produced which are later gradually used up in the light-independent reaction. Photosynthesis in important because it a) Produces the building blocks for complex compound in plants such as cellulose and lignin b) Provides the energy needed for chemical changes in the form of ATP c) Provides food to primary consumers (directly) and secondary (and higher) consumers (indirectly) d) Help reduce excess C02 and increase oxygen concentrations in the air.

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1. Explain the Photosystem I and Photosystem II.

A photosystem In the thylakoid membrane, chlorophyll is organized along with proteins and smaller organic molecules into photosystems A photosystem acts like a light-gathering “antenna complex” consisting of a few hundred chlorophyll a, chlorophyll b,and carotenoid molecules.

Each photosystem - reaction-center chlorophyll a and primary electron acceptor surrounded by an antenna complex - functions in the chloroplast as a light-harvesting unit.

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There are two types of photosystems. a. Photosystem I has a reaction center chlorophyll, the P700 center

absorption peak at 700nm. b. Photosystem II has a reaction center chlorophyll, the P680 center

-absorption peak at at 680nm. These two photosystems work together to use light energy to generate ATP and NADPH Location of the photosystems – thylakoids Process involved: •

Photoactivated of Photosystem I & Photosystem II

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Photolysis of water

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NADPH & ATP is produced

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Non-cyclic & cyclic photophosphorylation

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Photosystem Photosystem I & Photosystem II Photosystem I acts as its own, without photosystem II in cyclic photophosphorylation. While in Non-cyclic photophosphorilation photosystem I and Photosystem II involved.

Cyclic photophosphorylation.

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Non-cyclic photophosphorylation

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