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CLASS NOTES CHAPTER 8 – PHOTOSYNTHESIS ENERGY & LIFE 1. Life requires energy. 2. The sun is the source of energy. 3. Energy can change from one form to another. Examples: light, heat, electrical, chemical 4. Chlorophyll (chloroplasts) in green plants traps the sun’s energy and converts it into chemical energy (stored in bonds of glucose molecules) for use by all living things. OBTAINING ENERGY 1. autotroph (producer)– an organism that is able to use light energy from the sun to produce food “auto-“ means “self” “troph” means “to eat” example: plants, algae, some bacteria 2. heterotroph (consumer) – an organism that obtains energy from the other organisms “hetero-“ means “other” example: animals ENERGY 1. The activities of the cell are powered by chemical fuels. 2. ATP (adenosine triphosphate) “energy molecule” one of the principal chemical compounds that living organisms use to store energy composed of: a. adenine – nitrogen containing compound b. ribose – a sugar with 5 carbon molecules c. three phosphate groups 3. ADP (adenosine diphosphate) has a structure similar to ATP but it only has 2 phosphate groups 4. Releasing energy from ATP Energy is released when the P-P bond is broken ATP ADP + P + energy released 5. Storing energy in ADP Energy is stored when an additional P (phosphate group) is added to ADP ADP + P + energy added ATP 6. Electron transport chain Series of protein channels in membranes that pumps out H+ then slowly lets them back in through a protein channel. The back leak of H+ provides energy to add a phosphate (P) to ADP to form ATP NADPH is the electron carrier used in photosynthesis 7. Using Biochemical energy ATP provides energy to move ions across the cell membrane (active transport) ATP provides energy for movement within the cell ATP provides energy for the production and processing of proteins 8. ATP and Glucose ATP lasts for only a few seconds so it’s not efficient in storing large amounts of energy for long periods of time Glucose (sugar) stores more than 90 times the chemical energy as a molecule of ATP Therefore, it is more efficient for cells to keep only a small supply of ATP. Cells can produce ATP from ADP by breaking down glucose. PHOTOSYNTHESIS sunlight carbon dioxide + water glucose (sugar) + oxygen chlorophyll Chloroplast pigment – light absorbing molecule that absorbs the energy from the sun chlorophyll is the main pigment in plants 1. there are 2 types – chlorophyll a and chlorophyll b chlorophyll appears green because it reflects the green wavelength of light carotene –plant pigment that appears red and orange leaves appear green in the spring and summer because of active photosynthesis during the fall photosynthesis slows down, chlorophyll decreases and leaves appear red, orange and yellow due to the carotenes contains saclike membranes called thylakoids thylakoids are arranged in stacks called grana stroma – liquid like material found in the space of the chloroplast Composed of 2 parts: Light Reaction Calvin Cycle (Light independent Reaction) Light Reaction occurs in thylakoid membrane of chloroplast Sunlight is trapped by chlorophyll energy from the sun is stored in ATP water is split and oxygen is released. Hydrogen is used in the Calvin Cycle Electron transport chain- NADPH is formed. NADPH provides energy to make sugar in the Calvin cycle Calvin cycle (Light independent Reaction) Does not need light Occurs in stroma of chloroplast Carbon dioxide enters from the atmosphere Carbon from carbon dioxide is “fixed” (turned into) glucose. Sugar is released