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Photosynthesis

Photosynthesis. Bio 100 Tri-County Tec. College Pendleton, S. C. What are Pathways?. Pathways lead from one place to another Biochemical pathways contains reactions that are linked to each other the products of one reaction serve as the reactants of the next reaction A B C D E

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Photosynthesis

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  1. Photosynthesis Bio 100 Tri-County Tec. College Pendleton, S. C.

  2. What are Pathways? • Pathways lead from one place to another • Biochemical pathways • contains reactions that are linked to each other • the products of one reaction serve as the reactants of the next reaction • A B C D E • Usually there is an enzyme that catalyzes each reaction.

  3. The Major Pathways • Photosynthesis and respiration • Photosynthesis • occurs in green plants • carbon dioxide and water is converted into glucose • energy comes from the sun • chlorophyll is necessary • associated with chloroplasts in eukaryotes

  4. The Major Pathways • Respiration • carried out by all living organisms • glucose is converted to carbon dioxide and the energy in it is released as ATP • one form requires oxygen (aerobic) • some microorganisms can do respiration w/o oxygen (anaerobic) • associated with mitochondria in eukaryotes

  5. Autotrophs vs. Heterotrophs • Autotrophs • use sunlight and inorganic raw materials such as carbon dioxide to make glucose • green plants • Heterotrophs • use glucose from autotrophs to obtain energy • humans and other animals

  6. Photosynthesis

  7. Photosynthesis • Generalized Reaction • sunlight + 6CO2 + 6H2O  C6H12O6 + 6O2 • Green plants in the presence of sunlight take six carbon dioxide molecules and six water molecules and make glucose and six oxygen molecules. • Involves a light energy conversion stage and a carbon dioxide conversion stage

  8. Let there be light… • Light is form of electromagnetic energy traveling in waves that are composed of photons (discrete bundles of energy) • What one sees depends on absorption and/or reflection • ROY G BIV • Time to synthesize some information based on what is seen

  9. Light Energy Conversion-1 • 1. Oxidation-Reduction reactions (redox) • 2. Electrons are knocked loose from chlorophyll by sunlight. • 3. Some of those electrons are jacked up to a higher energy level and when they fall back the energy is used to make ATP. • 4. Cytochromes mediate the process. • 5. The electrons return to chlorophyll.

  10. Light Energy Conversion-2 • 5. Some of the excited electrons are captured by NADP which becomes negative and receives a H+ from the breakdown of water. • 6. The hydroxyl ions from the breakdown of water interact to form water, oxygen and free electrons.

  11. Light Energy Conversion-3 • The oxygen becomes a part of the atmosphere. • The water becomes a part of the water already in the plant cell. • The free electrons are accepted by chlorophyll that lost them to begin with.

  12. Light Energy Conversion-4 • The products of the light energy conversion stage-- • 1. usable energy as ATP • 2. source of usable hydrogen - NADPH • 3. water • 4. oxygen • Useful for the carbon dioxide conversion stage

  13. CO2 conversion • 1. CO2 (1C) is attached to ribulose (5C) using energy from the ATP generated by the LEC reactions resulting in a 6C compound. • 2. The 6C compound immediately breaks down into two 3C compounds (PGAL). • 3. Most of the PGAL is rearranged to form ribulose and the other intermediates in the process of photosynthesis.

  14. CO2 Conversion • 4. Two out of twelve PGAL’s (3C) are used for the production of Glucose (6C) and other substances. • Light energy conversion reactions take place in the grana of the chloroplasts. • Carbon dioxide conversion stage takes place in the stroma of the chloroplasts.

  15. What comes from what? • sunlight + 6CO2 + 6H2O  C6H12O6 + 6O2 • Sunlight comes from the sun • Carbon dioxide --- from animals and plants • Water -- from soil • Glucose -- primarily the CO2 conversion reactions • Oxygen -- light energy conversion react • C3, C4, and CAM plants • Cyanobacteria and their contribution

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