3.2 The leaf and photosynthesis

Photosynthesis The leaf is a collection of tissues working together to carry out photosynthesis. “Photo” “synthesis” (light) (putting together) [Putting together with light]

Photosynthesis The purpose of photosynthesis is to create energy Water + Carbon Dioxide ---------------------- Glucose + Oxygen chlorophyll +light 6 H2O(l) + 6 CO2(g) ----------------------> C6H12O6(aq) + 6O2(g)

Chloroplast Plant cells have organelles called chloroplasts chloroplasts contain a green pigment called chlorophyll cells containing chloroplasts are found in the ground tissue light energy is absorbed by chlorophyll and turned into chemical energy (food for the plant)

Accessory Pigments Chlorophyll is not the only pigment to capture light energy Accessory pigments help protect the plant and capture the most energy possible when temperatures get colder in the fall, chlorophyll disintegrates, revealing the other pigments underneath

Gas exchange in plants Two main reactions that take place in plants and produce gases as products Photosynthesis occurs in chloroplasts Occurs in the light Produces O2 and glucose Cellular respiration occurs in the cytoplasm and mitochondria Does not need light (as long as products from photosynthesis are available) Glucose + oxygen  carbon dioxide + water + energy C6H12O6 + 6O2  CO2 + H20 + energy

Gas exchange in plants Photorespiration the two processes together neither process can occur without the other

Observing photosynthesis What is an easy way to measure photosynthesis? Watch for a product of photosynthesis – OXYGEN

Something to think about: The estimated amount of global energy from photosynthesis is 1.0 x 1021 joules. That is 1000000000000000000000 joules A hydrogen bomb is rated at 4.2 x 1015 joules Photosynthesis produces the same energy as 238,095 hydrogen bombs!