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The conversion of light energy to chemical energy that is stored in sugars or other organic compounds; occurs in plants, algae, and certain prokaryotes |
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An organism that obtains organic food molecules without eating other organisms or substances derived from other organisms. Autotrophs use energy from the sun or from oxidation of inorganic substances to make organic molecules from inorganic ones. |
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An organism that obtains organic food molecules by eating other organisms or substances derived from them |
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Leaf cells specialized for photosynthesis. In C3 and CAM plants, mesophyll cells are located between the upper and lower epidermis; in C4 plants, they are located between the bundle-sheath cells and the epidermis. |
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A microscopic pore surrounded by guard cells in the epidermic of leaves and stems that allows gas exchange between the environment and the interior of the plant |
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The dense fluid within the chloroplast surrounding the thylakoid membrane and containing ribosomes and DNA; involved in the synthesis of organic molecules from CO2 and water |
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A flattened, membranous sac inside a chloroplast. Thylakoids often exist in stacks called grana that are interconnected; their membranes contain molecular "machinery" used to convert light energy to chemical energy |
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A green pigment located in membranes within the chloroplasts of plants and algae and in the membranes of certain prokaryotes. Chlorophyll a participates directly in the light reactions, which convert solar energy to chemical energy |
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The process of generating ATP from ADP and phosphate by means of chemiosmosis, using a proton-motive force generated across the thylakoid membrane of the chloroplast or the membrane of certain prokaryotes during the light reactions of photosynthesis |
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A quantum, or discrete quantity, of light energy that behaves as if it were a particle |
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An accessory pigment, either yellow or orange, in the chloroplasts of plants and in some prokaryotes. By absorbing wavelengths of light that chlorophyll cannot, carotenoids broaden the spectrum of colors that can drive photosynthesis |
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A light capturing unit located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes, consisting of a reaction-center complex surrounded by numerous light-harvesting complexes |
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Ribulose biphosphate carboxylase, the enzyme that catalyzes the first step of the Calvin cycle (the addition of CO2 to RuBP) |
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Glyceraldehyde 3-phosphate, the product of the Calvin cycle. Also serves as an intermediate in several central metabolic pathways in all organisms |
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A metabolic pathway that consumes oxygen and ATP, releases carbon dioxide, and decreases photosynthetic output. Generally occurs on hot, dry, bright days hen the stomata close and the O2/CO2 ratio in the leaf increases, favoring the binding of O2 rather than CO2 by rubisco |
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The two stages of photosythesis |
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The light reactions, in which solar energy is captured and transformed into chemical energy and the Calvin cycle, in which the chemical energy is used to make organic molecules of food |
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The original chloroplast was a photosynthetic prokaryote that lived in an ancestor of euk. cells |
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What drives the synthesis of organic molecules in the chloroplast? |
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The light energy absorbed by chlorophyll |
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6CO2+ 12H20 + Light energy = c6H12O6 + 6o2 + 6 H2O |
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the direction of electron flow |
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Photosynthesis as a redox process |
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CO2 becomes reduced to glucose, and 6 h20 becomes oxidized to 6 02 |
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Nicotinamide adenine dinucleotide phosphate |
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solar power to reduce NADP+ to NADPH by adding a pair of electrons along with an H+ |
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The light reactions generate |
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ATP, using chemiosmosis to power the addiction of a phosphate group to ADP |
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the initial incorporation of carbon from CO2 into an organic compound by an autotrophic organism (plant, photosynthetic organism, or a chemoautotrophic prokaryote) |
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The calvin cycle reduces the fixed carbon to |
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carbohydrate by addition of electrons. |
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The reducing power of the calvin cycle is provided by |
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NADPH, which acquired its electrons in the light reactions |
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Thylakoids or the chlotoplast are the sites of |
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Calvin cycle occurs in the |
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light is a form of energy known as |
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electromagnetic energy, which travels in rhythmic waves |
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substances that absorb visible light are known as |
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a graph that profiles the relative effectiveness of different wavelengths of radiation in driving a particular process |
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an action spectrum is prepared by |
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illuminating chloroplasts with light or different colors and then plotting wavelength against come measure of photosynthetic rate such as CO2 consumption or O2 release |
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an important function of some carotenoids , they absorb and dissipate excessive light energy that would otherwise damage chlorophyll or interact with oxygen forming reactive oxidative molecules that are dangerous to the cell |
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compounds with antioxidant properties |
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What happens when chlorophyll and other pigments absorb light? |
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The colors corresponding to the absorbed wavelengths disappear from the spectrum of the transmitted and reflected light, but energy cannot disappear |
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When a molecule absorbs a photon of light |
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one of the molecules electrons is elevated to an orbital where is has more potential energy, then the pigment molecule is excited |
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The only photons absorbed are |
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those whose energy is exactly equal to the energy difference between the ground state and an excited state |
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a complex of proteins associated with a special pair of chlorophyll a molecules and a primary electron acceptor. located centrally in a photosystem, this complex triggers the light reactions of photosynthesis. |
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excited by light energy, the pair of chlorophylls |
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donates an electron to the primary electron acceptor, which passes an electron to an ETC |
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light drives the synthesis of ATP and NADPH by |
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energizing the two photosystems embedded in the thylakoid membranes of chloroplasts |
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a route of electron flow during the light reactions of photosynthesis that involves both photosystems 1 and 2 and produces ATP, NADPH, and O2. The net electron flow is from H20 to NADP+ |
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a complex of proteins associated with pigment molecules (chlorophyll a, b, and carotenoids) that captures light energy and transfers it to reaction-center pigments in a photosystem |
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a route of electron flow during the light reactions of photosynthesis that involves only photosystem 1 and that produces ATP but not NADPH or O2 |
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an ETC assembled in a membrane pumps protons across the membrane as electrons are passed through a series of carriers that are progressively more electronegative. |
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redox energy to s proton motive force, potential energy stored in the form of an H+ gradient across a membrane |
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In chloroplasts the source of electrons |
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The thylakoid membrane of the chloroplast pumps protons from the |
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stoma into the thylakoid space which functions as the H+ resevoir |
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How do the reactant molecules of photosynthesis reach the chloroplast in leaves? |
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CO2 enters leaves via stomata and water enters via roots and is carried by leaves to veins |
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1. 6 carbon dioxide molecules combine with six 5-carbon molecules forming twelve 3-carbon molecules. |
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2. The 12 3-carbon molecules are converted into high-energy forms. |
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3. 2 of the 12 3-carbon molecules are removed and the plant uses them to produce sugars, lipids, amino acids, and other compounds. |
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Step four of Calvin Cycle |
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4. The 10 3-carbon molecules change back into six 5-carbon molecules, which combine with 6 more carbon dioxide molecules. |
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Explain why photorespiration lowers photosynthetic output for plants |
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Photorespiration decreases photosynthetic output by adding oxygen, instead of carbon dioxide to the calvin cycle. as a result, no sugar is generated (no carbon is fixed) and o2 is used rather than generated |
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