Overview & Purpose of Photosynthesis

1. Overview & Purpose of Photosynthesis Plants use sunlight to produce sugar = the plants food. Plant converts 6 molecules of H2O, 6 molecules of CO = 1 molecule of sugar and 6 molecules of O2. Manufacture food for the plant.

2. Equation of Photosynthesis 6CO2 + 6H2O + Energy ® C6H12O6 + 6O2

4. Structure of Mitochondria

5. Photosynthesis converts light energy into the chemical energy of sugars and other organic compounds. This process consists of a series of chemical reactions that require carbon dioxide (CO2) and water (H2O) and store chemical energy in the form of sugar. Light energy from light drives the reactions. Oxygen (O2) is a byproduct of photosynthesis and is released into the atmosphere. The following equation summarizes photosynthesis: 6 CO2 + 6 H2O → 6(CH2O) + 6 O2Sugar. Photosynthesis transfers electrons from water to energy-poor CO2 molecules, forming energy-rich sugar molecules. This electron transfer is an example of an oxidation-reduction process: the water is oxidized (loses electrons) and the CO2 is reduced (gains electrons). Photosynthesis uses light energy to drive the electrons from water to their more energetic states in the sugar products, thus converting solar energy into chemical energy. Notes for Thea six molecules of water plus six molecules of carbon dioxide produce one molecule of sugar plus six molecules of oxygen • The chloroplast is the organelle where photosynthesis occurs in photosynthetic eukaryotes. The organelle is surrounded by a double membrane. Inside the inner membrane is a complex mix of enzymes and water. This is called stroma and is important as the site of the dark reactions, more properly called the Calvin cycle. • Embedded in the stroma is a complex network of stacked sacs. Each stack is called a granum and each of the flattened sacs which make up the granum is called a thylakoid. Each thylakoid has a series of photosystems and associated proteins. The photosystems contain chlorophyll and other pigments and all these associated structures in the thylakoid membrane are the site for the light reactions in which light energy is converted to chemical energy needed for the Calvin cycle in the dark reaction. • As the light reactions proceed, the inside of the thlyakoid develops a high concentration of hydrogen ions, and this is important for the production of ATP by the chloroplast. • By the way, chloroplasts and related organelles, called plastids are believed to have arisen as free living bacteria that became symbiotic with the ancestors of photosynthetic eukaryotes. The cytoplasm of nearly all eukaryotic cells contain mitochondria, although there is at least one exception, the protistChaos (Pelomyxa) carolinensis. They are especially abundant in cells and parts of cells that are associated with active processes. For example, in flagellated protozoa or in mammalian sperm, mitochondria are concentrated around the base of the flagellum or flagella. In cardiac muscle, mitochondria surround the contractile elements. Hummingbird flight muscle is one of the richest sources of mitochondria known. Thus, from their distribution alone one would suspect that they are involved in energy production. Multicellular organisms probably could not exist without mitochondria. The inability to remove electrons from the system and the buildup of metabolic end products restrict the utility of anaerobic metabolism. Through oxidative phosphoryation mitochondria make efficient use of nutrient molecules. They are the reason that we need oxygen at all.