1. UNIT 5: PHOTOSYNTHESIS

2. PHOTOSYNTHETIC ORGANISMS  Include all land plants, algae such as kelp, Euglena, diatoms and cyanobacteria.  They are called autotrophs : Organisms that aren’t dependent on other organisms, they produce their own food.  They are producers that have the ability to synthesize carbohydrates, feed not only themselves but also consumers.  Collectively consumers are called: heterotrophs.

3.  Autotrophs and heterotrophs use organic molecules produced by photosynthesis as a source of building blocks for growth and repair and as a source of chemical energy for cellular work.  By-product of photosynthesizers is oxygen –  Oxygen is required by organisms for cellular respiration.  Oxygen rises high into the atmosphere, where it forms an ozone shield that filters out ultraviolet radiation and makes terrestrial life possible.

4.  Fossil fuel : Is coal formed by plants that died many year ago.  Ethanol is produced by the fermentation of plants and can be used to fuel cars or as an additive to gasoline. EUGLENA KELP EUGLENA CYANOBACTERIA

5. FLOWERING PLANTS AS PHOTOSINTHESIZERS  Photosynthesis takes place in the green portions of the plant.  Leaves have mesophyll tissue containing chloroplasts (organelle in plant cell in which photosynthesis occurs)  The raw materials of photosynthesis are: water, carbon dioxide and sunlight.

6.  Water is absorbed through the root hair into the xylem of the roots, into the xylem of the stem, through the xylem of the leaves into the mesophyll cells and finally into the chloroplasts.  Carbon dioxide diffuses from the atmosphere through the stomata, into the intercellular airspaces in the leaves, and finally into the chloroplasts of the mesophyll cells.  The chlorophyll and other pigments in the thylakoid membrane absorb the solar energy to drive photosynthesis.

7. Diagram of a chloroplast

8. Cross section through leaf

9. PROCESS OF PHOTOSYNTHESIS  Consists of 2 sets of reactions: 1.Light reaction (Dependent of light, occur in thylakoids of chloroplast, Raw materials are: Water and solar energy. End products are: oxygen[released to the atmosphere], NADPH and ATP [used in Calvin Cycle]) 2.Calvin Cycle/ Dark Phase (Independent of light, occur in stroma of chloroplast, Raw materials: Carbon dioxide and NADPH and ATP from light phase. End products: Carbohydrates).

10. Diagram showing the process of photosynthesis

11. Light reaction  Solar energy is absorbed by the chlorophyll pigments in the thylakoid membranes.  The electrons of the chlorophyll pigments are activated.  This energy is used to: -Split water (taken by the roots, transported through the xylem to the leaves) – 2H 2 O O 2 + 2H 2 – The oxygen is released into the atmosphere through the stomata. Process called: photolysis -The hydrogen is picked up by a hydrogen acceptor e.g. NADP to form NADPH. -Bond ADP (in Thylakoid) to a phosphate (in thylakoid) to form ATP (energy containing molecule). Process called: photophosphorylation