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Photosynthesis is… …the process through which plants convert light energy to chemical energy in order to produce food The energy involved in photosynthesis is eventually stored in the chemical bonds of molecules like glucose. Question A. B. C. D. Which of the following are necessary in order for photosynthesis to occur? Water, carbon dioxide, and light water Energy are all needed in order for light energy photosynthesis to occur. carbon dioxide all of the above Why are Plants Green? Objects appear a certain color because they reflect that color. Plants are filled with chlorophyll, a pigment that reflects green light. Plants absorb mostly red and blue light and reflect green light. Question A. B. C. D. In the simulation on the previous slide, the oxygen meter displays a negative number when the light is off. This is because the plant is undergoing photosynthesis. undergoing the Calvin cycle. undergoing cellular respiration. undergoing combustion reactions. Like all organisms that undergo aerobic cellular respiration, plants use oxygen to release the chemical energy stored in glucose and make ATP. Leaves contain chloroplasts. Chloroplasts are: – capsule-shaped organelles – contained by two membranes – located inside the mesophyll cells of leaves Question A. B. C. D. Where in a plant would you expect to find the greatest number of chloroplasts? root cells Within a leaf, the chloroplasts are concentrated in the inner layer of tissue, stomata cells which is known as the mesophyll. leaf vein cells mesophyll cells Question A. B. C. D. How do the mesophyll cells exchange gases with the outside environment? through simple diffusion through active transport through endocytosis and exocytosis through openings in the leaf called “stomata” Stomata allow carbon dioxide to be taken in and oxygen and water vapor to exit. For this reason, most plants keep their stomata closed for most of the day, when evaporation is more likely. Chloroplast Parts Thylakoids: disk-shaped vesicles stacked inside the chloroplast Granum: a stack of thylakoids Stroma: liquid material inside the chloroplast Chlorophyll: pigment located inside the thylakoid that absorbs light energy; gives plants their green color Chlorophyll Question Complete the following analogy. mitochondrion : matrix :: chloroplast : _______ A. stroma Both the matrix and the stroma are B. granum metabolically-active, fluid-filled areas inside the innermost membranes of the C. thylakoid organelle of which they are a part. D. inner membrane Light-Dependent Reactions In this set of reactions, the energy in sunlight is captured and used to make energy-storing compounds. (ATP & NADPH) These reactions take place inside the thylakoid membranes. Also known as the “Light Reactions.” Four Processes of the Light-Dependent Reactions 1. 2. 3. 4. Light Absorption Electron Transport Oxygen Production ATP Formation Question A. B. C. D. What is the first step in the light-dependent reactions? formation of ATP Light initiates the process of photosynthesis by energizing the absorption of light electrons in the reaction-centers production of oxygen of photosystems I & II. transport of electrons The Light-Independent Reactions Includes the Calvin cycle. Light does not play a role in these reactions; they can take place in the light or the dark. Sometimes misleadingly called the “dark reactions.” Question A. B. C. D. Why is it misleading to call the Calvin cycle reactions the “dark reactions?” They cannot happen in the dark. They can only happen in the light. They can only happen in the dark. They can happen any time—light or dark. These reactions are not dependent on light energy. They can occur as long as CO2, ATP, and NADPH are present. The Calvin Cycle The light independent reactions form a cycle, or circular series of reactions. – This cycle is called the “Calvin Cycle” after the person who first described it, Melvin Calvin. This is as detailed as we’ll get! The Calvin Cycle uses CO2 along with ATP and NADPH from the light reactions to form the building blocks for glucose.