3.1 Overveiw of Photosynthesis
Site of photosynthesis - the leaf
structure of the leaf
They are adapted to bring together the three raw materials of photosynthesis. (water, carbon dioxide and light) and remove its produts (oxygen and glucose). These adaptations include.
- A large surface area that collects as much sunlight as possible.
- an arrangement of leaves on the plat that minimises overlapping and so avoids the shadowing of one leaf by another.
- thin, as most light is absorbed in the first few millimetres of the leaf and the diffusion distance is thus kept short.
- a transparent cuticle and epidermis that let light through to the photosynthetic mesophyll cells beneath.
- Long narrow, upper mesophyll cells packed with chloroplasts that collect sunlight.
-Numerous stomata for gaseous exchange
- Stomata that open and close in response to changes in light intensity
- Many air spaces int he lower mesophyll layer to allow diffusion of CO2 and oxygen.
- a network of xylem that brings water to the leaf cells and phloem that carries away the sugers produced in photosynthesis
6CO2 + 6H20 --> C6H12O6 + 6O2
1. Capturing of light energy - by chloroplast pigments such as chlorophyll
2. The light independant reaction - in which light energy is converted into chemical energy. During the process an electron flow is created by the effect of light on chlorophyll and this causes water to split (photolysis) into protons, electrons and oxygen. The products are reduced NADP, ATP and oxygen.
3. The light-independant reaction - in which these protons (hydrogen ions) are used to recude carbon dioxide to produce sugars and other organic molecules.
Structure and role of chloroplasts in photosynthes
Photosynthesis takes place within cell organelles called chloroplasts, the