Exam 2 Material Part 1

Exam 2 Material Part 1 - EXAM 1: up through translocation;...

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EXAM 1: up through translocation; plant nutrition and Friday’s lecture will be covered in exam II. Not responsible for CAM, but do need to know the basics of C4. I. Transport of sugars From last lecture: Triose (3-carbon sugar) phosphate: glyceraldehyde-3-phosphate can exit the Calvin cycle In the cytoplasm, synthesized into glucose. Or stays in the chloroplast, synthesized into starch. What happens when glucose builds up in the cytoplasm? Synthesized into sucrose: glucose + fructose and transported to other regions of the plant. A. the direction of translocation : the process of moving sugars to other parts of the plant. The direction of translocation is determined by where the sugars are needed and are being used, i.e. sinks, so we say that Translocation in plants occurs from SOURCES TO SINKS. SOURCES are actively photosynthesizing leaves. SINKS are organs that consume or store sugar: developing roots, roots specialized for strorage developing shoots, storage stems, and fruit formation
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Developing leaves generally require more sugar to expand fully than they can provide themselves, so they are initially sinks, where as once they are mature and actively photosynthesizing, the same leaves becomes a source. Therefore, translocation of photosynthates can be either up or down in a plant. Short distance transport: from mesophyll cell where chloroplasts are to the sieve tube members in the vascular bundles of the leaf B. Phloem loading 1. What happens to the sucrose produced by the Calvin cycle Sucrose moves from mesophyll cells to mesophyll cell to a vascular bundle in the leaf via symplastic or a combination of symplastic and apoplastic transport. From here, sugars are transported in into sieve tube members through a process called 2. phloem loading : REQUIRES ENERGY because these sugars are ACTIVELY transported from the surrounding parenchyma cells
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This test prep was uploaded on 04/07/2008 for the course BIOL 108 taught by Professor Jones/smith during the Spring '08 term at UConn.

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Exam 2 Material Part 1 - EXAM 1: up through translocation;...

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