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| living things need energy to survive. energy comes from food. energy in food comes from sunlight. |
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| plants and some other types of organisms are able to use light energy from the sun to produce food. organisms that make their own food are autotrophs. |
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| organisms, such as animals, that must obtain energy from foods they consume are heterotrophs. |
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| an important chemical compound that cells use to store and release energy also called adenosine triphosphate. used by all types of cells as they basic energy source. consists of: adenine, ribose (5 carbon sugar), and 3 phosphate groups (key to ATP's ability to store and release energy) |
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| has 2 phosphate groups instead of 3. a cell can store small amounts of energy by adding a phosphate group to ADP. |
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| the key cellular process identified with energy production. the process in which green plants use the energy of sunlight to convert water and carbon dioxide into high energy carbohydrates and oxygen |
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| wanted to see if plants got their food and energy by taking material out of the soil- proved false. he concluded that it actually came from the water, which was true but he only got part of it. he didn't realize carbon dioxide also played a major role. |
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| Priestley put a candle under a jar and watched the flame die- concluded that the flame needed oxygen to stay lit. then he put a plant under the jar with the candle and the flame relit- he concluded that the plant released oxygen. |
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| showed that the effect observed by Priestley occurred only when the plant was exposed to light- concluded light is necessary for plants to produce oxygen. |
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| Van Helmont + Priestley + Ingenhousz = |
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| in the presence of light, plants transform carbon dioxide and water into carbohydrates and they also release oxygen |
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| equation for photosunthesis |
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6CO2 + 6H2O → C6H12O6 + 6O2
carbon dioxide + water →(light) sugar + oxygen |
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| photosynthesis also requires light and chlorophyll. plants gather suns energy with light absorbing molecules called pigments. main plant pigment- chlorophyll. light is a form of energy so any compound that absorbs light also absorbs energy from that light. |
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| 2 main types of chlorophyll- chlorophyll a and chlorophyll b. chlorophyll absorbs light well in the blue-violet and red regions of the visible spectrum. chlorophyll does not absorb light well in the green region of the spectrum, green light is reflected by leaves- why plants look green. when chlorophyll absorbs light, much of the energy is transferred directly to electrons in chlorophyll molecule, raising energy levels of electrons. high energy electrons make photosynthesis work. |
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| photosynthesis in plants takes place inside chloroplasts |
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| chloroplasts contain thylakoids- saclike photosynthetic membranes. |
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| thylakoids are arranged in stacks known as grana. a singular stack is a granum. |
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| proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems, which are the light collecting units of the chloroplast |
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| reactions of photosystems |
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| light-dependent reactions and the light-independent aka Calvin cycle |
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| light-dependent reactions take place within the thylakoid membranes and the calvin takes place in the stroma |
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| region outside the thylakoid membranes |
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| when sunlight is absorbed, electrons gain a great deal of energy. cells use electron carriers to transport these high-energy electrons from chlorophyll to other molecules. one carrier molecule is NADP+ |
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| transports electrons. accepts and holds 2 high energy electrons along with a hydrogen ion (H+) which converts NADP+ into NADPH. this conversion is one way some of the energy of sunlight can be trapped in chemical form. |
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| NADPH carries high energy electrons to chemical reactions elsewhere in the cell. these high energy electrons are used to help build a variety of molecules the cell needs including carbohydrates like glucose |
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| light-dependent reactions |
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use energy from sunlight to produce oxygen gas and convert ADP and NADP+ into energy carriers ATP and NADPH
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| light-dependent reaction steps |
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- photosystem II- light absorbed by photosystem II is used to break up water molecules into energized electrons- hydrogen ions and oxygen
- electron transport chain- high energy electrons from photosystem II move thru electron transport chain to photosystem I
- photosystem I- electrons released by photosystem II are energized again in photosystem I. enzymes in the membrane use the electrons to form NADPH. NADPH is used to make sugar in the Calvin Cycle.
- hydrogen ion movement- the inside of the thylakoid membrane fills us with positively charged hydrogen ions. this action makes the outside of the thylakoid membrane negatively charged and the inside positively charged.
- ATP formation- as hydrogen ions pass thru ATP synthase, their energy is used to convert ADP into ATP
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| uses ATP and NADPH to produce high energy sugars. takes place in the stroma and does not require light. |
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- CO2 enters the cycle- 6 carbon dioxide molecules are combined with six 5-carbon molecules to produce twelve 3-carbon molecules
- energy input- energy from ATP and high energy electrons from NADPH are used to convert the twelve 3-carbon molecules into higher energy forms
- 5-carbon molecules regenerated- the 10 remaining 3-carbon molecules are converted back into six 5-carbon molecules, which are used in the next cycle
- 6-carbon sugar produced- two 3-carbon molecules are removed from the cycle to produce sugars, lipids, amino acids, and other compounds.
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| factors affecting photosynthesis |
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| water, temperature, and intensity of light |
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