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Chapters 7 and 8 Photosynthesis and Respiration What Is Photosynthesis? • The process by which photosynthetic organisms construct carbohydrates, using: The energy from sunlight The carbon and oxygen from CO2 The hydrogen from water • Oxygen from water released as waste product • Photosynthetic organisms include plants, algae, some bacteria What Is Respiration? • The process by which most living organisms get their energy from food, using: The chemical energy stored in the food Oxygen (O2) • Waste products: CO2 (released by us as a gas) H2O (also released by us as a gas) • All eukaryotic organisms (and some prokaryotes) carry out aerobic (oxygenconsuming) respiration to get their energy Linked Processes Photosynthesis Respiration • Energy-storing pathway • Energy-releasing pathway • Releases oxygen • Consumes oxygen • Consumes carbon dioxide • Releases carbon dioxide Inputs and Outputs of Photosynthesis Inputs Outputs • Energy (from sunlight) • Carbohydrates (e.g., C6H12O6, glucose) • CO2 (from air) • H2O (from soil) • O2 gas (released to atmosphere) 6 CO2 + 6 H2O + Energy C6H12O6 + 6O2 (Net photosynthetic equation) Inputs and Outputs of Respiration Inputs Outputs • Carbohydrates (e.g., C6H12O6, glucose) • Energy (in chemical form) • O2 gas • H2O C6H12O6 + 6O2 • CO2 6 CO2 + 6 H2O + Energy (Net respiration equation) Visible Spectrum for Photosynthesis Visible violet light transitions into invisible ultraviolet radiation Visible red light transitions into invisible infrared radiation Chlorophyll: Main Light-Absorbing Pigment Chlorophyll a Wavelength absorption (%) Light absorbances by chlorophylls a and b are slightly different chlorophyll a chlorophyll b Wavelength (nanometers) Photosynthesis and Leaf Cells Chloroplasts • In plants and algae, photosynthesis occurs inside specialized organelles, chloroplasts • Chloroplasts are bacteria-sized, so a large plant cell may contain hundreds of them • They contain many internal membranes, enclosing small compartments called thylakoids • Chlorophyll and other light-absorbing pigments are located in the thylakoid membranes Chloroplast Structure Chloroplast Thylakoid membrane, a much-folded single flattened compartment inside the stroma two outer membranes stroma (semifluid interior)
