2. Handy Definitions: 1. Chloroplasts are double membrane organelles with the an inner membrane folded into disc-shaped sacs called thylakoids. 2. Thylakoids, containing chlorophyll and other accessory pigments , are in stacks called granum. 3. Grana are connected to each other & surrounded by a gel-like material called stroma.
3. Light Dependent Reaction: (Light Reaction) Using energy from the sun, water; taken in through transcription, is split. Transcription is the process when water is pulled into a plant from the surface exposed to the out side, for example, how the water moves from sitting on a leaf to the inside of the leaf. Light from the sun hits the chloroplasts activating an enzyme which then breaks apart the water. When the water is broken down makes oxygen, hydrogen, and electrons. The hydrogen is converted into NADPH and then used in the independent reactions. The oxygen leaves the plant as a waste product. Electrons are passed through a series of carriers and adenosine triphosphate or ATP (energy) is produced. This process takes place in the thylakoids.
4. Light Independent Reaction: (Dark Reaction) The light independent reaction would not be possible without the light dependent reaction. During this process carbon dioxide is split which is then used to make sugars. The ending product is glucose. Even though this process depends on the products of light dependent reactions, light energy is not directly required. A process known as the Calvin Cycle is included. This reaction takes place in the stroma.
5. Calvin Cycle Step 1: - CO2 diffuses into the stroma from cytosol. - An enzyme combines a CO2 molecule with a five-carbon carbohydrate called RuBP. - The resulting six-carbon molecule then splits into a pair of three-carbon molecules called PGA. Step 2: -Each PGA molecule receives a phosphate group from a molecule of ATP. -This compound then receives a proton from NADPH and releases a phosphate group producing PGAL. -The reactions make ADP, NADP+, and phosphate which are used again in the Light Reactions. Step 3: -Most PGAL is converted back to RuBP to keep the Calvin cycle going. -Some PGAL leaves the Calvin Cycle and is used to make other organic compounds including amino acids, lipids, and carbohydrates. -PGAL serves as the starting material for the synthesis of glucose and fructose. -Glucose and fructose make the disaccharide sucrose, which travels in solution to other parts of the plant (e.g., fruit, roots).
