1 Photosynthesis Part I

2 I. Photosynthesis A. The process by which green plants use sunlight energy to convert water & carbon dioxide into oxygen & glucose is the basis for virtually all life. Sugars, the first products of photosynthesis, are converted into starch, protein, cellulose, and thousands of other chemical compounds.

3 Video overview of photosynthesis

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5 B. Photosynthesis is a very important process for the following reasons 1. During photosynthesis, green plants trap the energy from the Sun. This energy is passed on to organisms that depend directly or indirectly on green plants for food. Food Chain 2. Photosynthesis replenishes the oxygen that has been used up by organisms during respiration. 3.Photosynthesis purifies the air by removing the carbon dioxide that is given out by organisms during respiration

6 II. Autotrophs A. Organisms that make their own food B.They must make carbohydrates to then make ATP

7 III. Internal Structure of a Leaf A. Function-To trap the sun energy for photosynthesis B. Xylem- Network of veins for water C. Pholem- Network of veins for food D. Spongy Mesophyll- Some photosynthesis takes place-air spaces (CO 2 and water vapor) E. Palisade Mesophyll- Most of the photosynthesis takes place here. Contains up to 500 chloroplast per cell

8 Internal Structure of a Leaf F. Epidermis- covers lower and upper surface G. Cuticle-waxy water repellent Adaptations of Plants… thin leaves, thick cuticle

9 Internal Structure of a Leaf F.Stomates- Gas Exchange/ Minute pores in the epidermis G. Guard Cells- in the stomates swell with water to open H. Transpiration- Evaporation of water

10 IV. Site of Photosynthesis-Chloroplast A. Stroma, a semi-fluid material that contains dissolved enzymes, DNA, RNA and ribosomes B. Thylakoids stacks of closed hollow disks - increased absorption of light(stacks of these are called grana)

11 Site of Photosynthesis C. Light travels as packets of energy called photons and is absorbed in this form by light-absorbing chlorophyll molecules embedded in the thylakoid disks.

12 Site of Photosynthesis D. When the chlorophyll molecules inside the thylakoids absorb the photons, they emit electrons. The free electrons are then taken up by molecules in the stroma to produce ATP (adenosine triphosphate).

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14 V.Photosynthesis Reactants and Products A. Photosynthesis can be simplified into two reactants:carbon dioxide and water and two products:glucose and oxygen, represented by the chemical equation: