311DCh39 - Ch 39 pg 821 849;790 Etiolation morphological...

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Ch. 39 pg. 821 – 849;790 Etiolation – morphological adaptations for growing in darkness De-Etiolation – “greening”; when a shoot reaches sunlight the plant undergoes changes; elongation of stem slows, leaves expand; roots elongate; shoot produces chlorophyll Receptors – proteins that undergo conformational changes in response to a specific stimulus Phyotchrome – a photoreceptor; receptor involved in de-etiolation; occurs in cytoplasm Second messengers – small, internally produced chemicals that transfer and amplify the signal from the receptor to other proteins that cause the response; each activated phytochrome molecule may give rise to hundreds of molecules of secondary messengers Light causes phytochrome to undergo change that leads to increases in second messengers cyclic GMP (cGMP) and Ca2+. Changes in cGMP levels leads to ionic changes within the cell and activates protein kinases that activate other enzymes via phosphorylation; activation of phytochrome can open Ca channels and increase cytosolic levels to influence other channels and kinases Two mechanisms signal pathway can activate an enzyme: 1. Stimulating transcription of mRNA for enzyme (transcriptional
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This note was uploaded on 02/01/2011 for the course BIO 311D taught by Professor Reichler during the Spring '08 term at University of Texas.

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311DCh39 - Ch 39 pg 821 849;790 Etiolation morphological...

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