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Biology Final Reading Notes

Biology Final Reading Notes - Biology Final Reading Notes...

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Biology Final Reading Notes Chapter 39 :821-835 Potatoe Plant o Etiolation- adaptations for growing in darkness o Deetolation- when the plant reaches light and leaves expand and stem elongation slows Cell Signaling Process Reception Signals are first detected by receptors Proteins that undergo changes in shape in response to a specific stimulus Receptor for detolation is in the cytoplasm (phytochrome) Transduction Transduction of weak signals involves second messengers Second messenger – small molecules and ions in the cell that amplify the signal and transfer it from the receptor to other proteins that carry out the response Signal Transductin in plants: The role of phytochrome in the de-etiolation (greening) response Second messengers- Ca^2+, cGMP Phytochrome Activation by light Opens two signal transduction pathways: o opens ca channels increasing the low concentration o phytochrome changes shape activation guanylyl cyclase enzyme that produces cGMP Response Two main mechanisms by which a signaling pathway can enhance an enzymatic step in a biochemical pathway Post Translational modification – activates pre existing enzymes Preexisting proteins are modified by phosphorylation of specific amino acids which alters the proteins hydrophobicity and activity -cGMP and Ca activate protein kinases directly
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Transcription regulation - increases or decreases the synthesis of mRNA encoding a specific enzyme Transcription factors are activated by phosphorylation in response to the appropriate light conditions The activation of these factors depends on their phosphorylation by protein kinases activated by cGMP or Ca The mechanism by which a signal promotes developmental changes depends on transcription factors Activators increase the transcription of genes Repressors decrease transcription Plant Hormones Hormone- signaling molecule that is produced in tiny amount and transported to other parts of
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