Plants make food. Food is good. PHOTOSYNTHESIS Plants make food. Food is good.

Equation Used to seeing: 6CO2 + 6H2O  6O2 + C6H12O6 6 molecules of water have been added to each side of the equation. This is to show that all of the oxygen released comes from the water, not the carbon dioxide. Equation

Energy from sunlight is absorbed by chlorophyll pigment in the chloroplasts of green plant cells and is converted to chemical energy. Some of the energy is used to split water molecules into hydrogen and oxygen. It occurs on the internal membranes of the chloroplasts (thylakoids) in plant cells. Light reactions

Are you smarter than an 8th grader? The energy captured by chlorophyll is sufficient to excite an electron to a higher energy level, where it will break away from a chlorophyll molecule. This series of reactions is occuring in each chlorophyll molecule in every chloroplast exposed to light and there are thousands of chlorophyll molecules in one chloroplast so thousands of excited electrons are produced. Are you smarter than an 8th grader?

An excited electron can follow one of two paths: It may be used to split water into a hydrogen component (H2) and an oxygen atom (O). The oxygen atom combines with an oxygen atom from another chlorophyll molecule to form oxygen gas (O2), which is released by the plant. Hydrogen atoms move on to next phase. It may be used to form ATP, a high-energy compound that provides the cell with the energy it needs for functioning. Excited Electrons

Light-independent Reactions Hydrogen released from the first reaction combines with carbon dioxide to form sugars. This process requires energy but does not need chlorophyll or light. The energy needed is supplied from some of the energy absorbed from light in the first set of reactions in photosynthesis or from energy stores (ATP) in the plant. These reactions happen in the stroma or fluid matrix of the chloroplasts. At least two different pathways are known. Light-independent Reactions

Hydrogen atoms from the light reaction are carried to the stroma to begin this phase Carbon dioxide needed for this reaction was absorbed by the plant from surrounding air The hydrogen atoms go through a series of enzyme-controlled reactions where they are combined with carbon dioxide to form a sugar molecule (glucose) The glucose end-product of photosynthesis is converted to starch, the form in which food is commonly stored in plants. Calvin/not Calvin?

Summary Light-independent phase Light Phase The radiant energy of sunlight is captured by chlorophyll and used to split water into hydrogen and oxygen. The oxygen is released by the plant into the atmosphere. The hydrogen is carried on to the next phase. The hydrogen atoms from the light reaction are combined with carbon dioxide to form sugar molecules. The carbon and oxygen atoms of the sugar come from CO2 The hydrogen atoms of the sugar come from the water. The oxygen that is released in the light stage also comes from the water. Summary