5A_Photosynthesis


 * __6th May 2010__**

- The process whereby energy from the sun us converted into chemical energy that can be utlized by plants and other organisms. - Oxygen is released as a product
 * __Photosynthesis__**

- Through Photosynthetic pigments - Mainly __Chlorophyl__l - chlorophyll a, b (absorb blue and red, reflects green) - Accessory pigments: - __Phycocyanin__ (absorb green and yellow, reflect yellow, orange or red) - __Carotenoids__ (absorb blue and green reflect mostly yellow)
 * How is light absorbed?**

- The two kinds of chlorophyll complement each other in absorbing sunlight. Plants can obtain all their energy requirements from the bue and red parts of the spectrum, however, there is still a large spectral region, between 500-600nm, where very little light is absorbed
 * Absorption spectra of chlorophyll**

- As the chlorophyll in leaves decays in the autumn, the green colour fades and is replaced by the orange and reds of carotenoids.
 * Why do leaves change colours?**

- Organelles responsible for photosynthesis - Consists of a soluble membrane enclosing a semi fluid medium - Interior comprise of disk shaped interconnected sacs known as thylakoids - Stroma - space bound my membrane - Photosynthesis occurs within the membrane of the thylakoids.
 * Chloroplasts**

- Via vessels running from the root, through the stem to the leaves - Xylem - vessels for conducting water - Phloem - vessels for conducting nutrients
 * How do plants absorb water?**

- Via openings on the leaf surface known as __stomata__ - How does the plant control the opening and closing of the stomata? - Stomata take in AIR and water gets evaporated, so it is underneath so that not too much sunlight evaporates the water so fast. - More photosynthesis -> increase osmotic potential -> decrease water potential -> outside cell with higher water potential, water move in and it becomes turgid - When it is photosynthesising, the stomata will open, when it isnt, the stomata will close
 * How does air enter the plant?**

- The palisade mesophyll is arranged that such that it is perpendicular to the upper epidermis for optimum sunlight absorbed
 * How are plants adapted for optimal photosynthesis?**

- Energy from sun splits water to form oxygen - Solar energy is converted to chemical energy - ATP & NADPH used by plants (energy) - ATP -> ADP -> AMP (each time it releases energy)
 * Summary**

- Boil in hot water to destroy all enzymes to stop reaction - Add ethanol to dissolve the fats of the plasme cell membrane, causing the chlorophyll to leak out and become decoloured
 * Experiment**

- As light intensity increases, the rate of photosynthesis increases - There is a limit to the maximum rate (saturation point) - At the saturation point, the rate of photosynthesis cannot increase due to the presence of a limiting factor - Only by increasing the limiting factor can the rate increase. - Eg. Pump in more carbon dioxide
 * Rate of photosynthesis against light intensity**

PLANTS HAVE DIFFERENT COLOURED PIGMENTS, but we always see the leaves as green but the flowers and fruits will show certain colours more.

Plants store glucose as starch so as not to increase osmotic concentration. Starch is insoluble, highly immobile, does not react with anything in the cell, large molecule: GOOD STORAGE THING

Too hot -> plant shrivel up and die Too cold -> not heat to break up the water molecules -> cannot photosynthesise -> diess - Irregular cells with large intercellular space || - Generally found at the lower surface area to cut down on water lost through transpiration || - Large surface area - Air that enters at the lower layer still can reach the top layer - Leaf stalk and vein to help the leaf stay upright and expose the max. surface area to sunlight (vascular bundle) || - Decrease water potential || - Focus the light to let the palisade mesophyll absorb more amount of light ||
 * < Name ||< Function ||
 * < Spongey mesophyll ||< - Found at the bottom layer as there are more stomata there
 * < Stomata ||< - Holes that have regulated size to allow gaseous exchange
 * < Leaf ||< - Thin and flat
 * < Vascular Bundle ||< - Transport system for water and nutrients
 * Epidermal Layer || - Transparent