Excess salt in the gut causes water inflow by osmosis resulting in profuse

Excess salt in the gut causes water inflow by osmosis

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Excess salt in the gut causes water inflow by osmosis, resulting in profuse diarrhea and consequent dehydration and electrolyte imbalance. Not good.
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Transduction: Ca 2+ , another 2 nd messenger Normally Ca ++ concentration in the cytosol (cytoplasm fluid) is kept low. It can be 10,000 times less concentrated in the cytosol than in blood. Ca ++ is pumped out of the cell or into the endoplasmic reticulum (darker blue = more Ca ++ ). If Ca ++ is increased in the cytosol, this can cause a variety of reactions depending on the cell type, such as muscle cell contraction, secretion of cell produces, & cell division.
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Transduction via 2 nd messengers IP3 and Ca ++ G-protein Phospholipase inositol trisphosphate (IP3) IP3 is a 2nd messenger made of a membrane phospholipid IP3 acts as a ligand and activates a ligand-gated Ca ++ channel in the endoplasmic reticulum Ca ++ zooms out of the ER by diffusion. Ca ++ does its thing, often via activating a protein called calmodulin, which is a Ca 2+ binding protein that activates protein kinases or protein phosphatases lumen
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Cellular responses include: -Rearrangement of cytoskeleton (e.g., for cell movement) -Transcription by activation of protein factors -Regulation of cell metabolism (e.g., breakdown of sugars) Following transduction, cellular responses to signals
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Transcription response. The transcription response is similar to what we saw for testosterone, except in this case it is activated by a series of transduction steps.
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Signal amplification One signal molecule causes a huge response. hundreds of millions of glucoses are released Epinephrine example, and the breakdown of glycogen
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Cellular response: Specificity Epinephrine as a signal molecule affects liver cells differently than heart cells -Liver breaks down glycogen to produce glucose -Heart cells (muscles) contract – pump faster to move blood (and the glucose produced in the liver) around the body so it can reach muscle cells Why the different responses? Because receptor and transduction proteins control a cell’s responses, and different cell types have different collections (types) of receptors and transduction proteins.
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Cellular response: Specificity One signal molecule can yield different results depending upon cell type A. Single response by a cell B. Dual response by a cell C. Cross-talk (cooperation) among receptors, controlling transduction D. Single response, but different receptor in a different kind of cell. A B C D
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Cellular response: speed Molecules must diffuse through the cytoplasm to interact. Proteins move slowly because of their size (much more slowly than 2 nd messengers) To improve speed, signaling-pathway enzymes may be attached to scaffolds that hold them in adjacent positions, so they can activate the next protein more rapidly.
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