Biology Lecture 14 - Exam 3
Biology Lecture 14 - Exam 3 BIO 121 A
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This 2 page Class Notes was uploaded by Devin Mart on Friday March 25, 2016. The Class Notes belongs to BIO 121 A at Missouri State University taught by Dr. Durham in Spring 2016. Since its upload, it has received 10 views. For similar materials see General Biology in Biology at Missouri State University.
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Date Created: 03/25/16
Mart 1 Lecture 14: Photosynthesis ● Plants and other autotrophs are the producers of the biosphere. ○ Photosynthesis is the process by which plants use sunlight to synthesize foods, this nourishes the living world directly and indirectly. ○ Autotrophs produce organic molecules from CO₂ and other inorganic raw materials, these can be separated by the source of energy that drives their metabolism. ■ Polyautotrophs use light as their energy source, ex. plants, algae. ■ Chemoautotrophs use energy from oxidizing inorganic substances, including sulfur and ammonia, ex. Bacteria. ○ Heterotrophs live on organic compounds produced by other organisms, the consumers of the biosphere. ● Chloroplasts are the site of photosynthesis within a plant. ○ Chlorophyll is a green pigment responsible for the absorption of light to provide energy for photosynthesis. ○ Chloroplasts are mainly found in mesophyll cells. ■ O₂ exits the cell while CO enters the leaf through tstomata. ● The primary pathway of photosynthesis is this reaction, CO₂ + 2H₂ O → CH₂ O + H₂ O + O₂ . ○ Light reactions convert solar energy to chemical energy. ■ Energy captured from light by the chlorophyll drives the production of ATP, through the process of photophosphorylation, the source of energy that is later used to drive the production of carbohydrates. ○ The Calvin cycle is the set of chemical reactions that take place in chloroplasts during photosynthesis, the cycle is lightindependent because it takes place after the energy has been captured from sunlight. ■ The Calvin Cycle incorporates CO₂ into an organic molecule vicarbon fixation ○ The action spectrum measures the change in photosynthetic activity as wavelength varies, this is unique for each pigment. ○ There are two possible routes for electron flow: ■ Noncyclic electron flow produces both ATP and NADPH. ■ Cyclic electron flow is a process of biasing light reaction outputs so that photophosphorylation is increased. ○ Chloroplasts and mitochondria generate ATP by the same mechanism: chemiosmosis. ● The Calvin cycle converts CO₂ to sugar. Mart 2 ○ The use of ATP and NADPH allows the cycle to generate sugar, glyceraldehyde3phosphate (G3P). ○ Rubisco is an enzyme present in chloroplasts, involved in fixing carbon dioxide during photosynthesis and in oxygenation of the resulting compound during photorespiration., this is a key enzyme. ■ C₃ plants is during the stage in photosynthesis in which the carbon is split into a 3 carbon sugar, 3phosphoglycerate. ● Photorespiration is a respiratory process in plants by which they take up oxygen in the light and give out some CO₂ . ■ C₄ plants is the stage in photosynthesis in which the CO₂ is fixed into a fourcarbon compound. ● Mesophyll cells incorporate CO₂ into organic molecules. ● PEP carboxylase fixes CO₂ efficiently. ○ Crassulacean acid metabolism (CAM) is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. ■ In a plant using CAM, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide. ● On a global scale, photosynthesis is the most important process to the welfare of life on Earth.
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