Unit 2: Metabolic Processes Photosynthetic Organisms SBI4U – Ms. Richardson

Photosynthesis Purpose: Location: General Equation To synthesize carbohydrates (ie. glucose) using the Sun’s energy Location: Chloroplast General Equation 6CO2 + 6H2O  C6H12O6 + 6O2 Visible Light Chlorophyll

Photosynthetic Organisms Includes plants, algae, some protists and cyanobacteria All contain chlorophyll green-coloured pigment Absorbs light energy Several types: Chlorophyll a (blue-green), contains methyl group Chlorophyll b (yellow-green), contains aldehyde group

Photosynthetic Organisms Chlorophyll is composed of a porphyrin ring attached to hydrocarbon chain Porphyrin contains magnesium atom Delocalized electrons within porphyrin absorb light energy Hydrocarbon tail (phytol tail) anchors the molecule within the cell membrane

Prokaryotic Autotrophs Cyanobacteria (blue-green algae) Unicellular First photosynthetic organisms Largest group of photosynthesizing prokaryotes Blooms often develop in water that has high nitrate and phosphate levels

Eukaryotic Autotrophs: Algae, Protists & Plants Chlorophyll contained within chloroplasts Chloroplasts are only located in leaves, stems, and unripened fruit

Leaves Function: Structure: photosynthesis maximizes surface area exposed to light limits distance for gases to travel to reach chloroplast

Leaves

Transpiration Loss of water vapour in plants, primarily through stomata Assists photosynthesis: Transpiration pull Evaporative cooling

Stomata Controls gas exchange Guard cells swell when K+ ions and water move into guard cells Stomata close (night) When K+ ions and water move out of guard cells, they become flaccid Stomata open (day) CO2 absorbed

Chloroplasts Site of photosynthesis Occurs mainly in stroma and thylakoid membrane Contain their own DNA and ribosomes May contain starch an lipids