Ion Transport, Resting Potential, and Cellular Homeostasis ...
Maintaining Cellular Homeostasis
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Transcript of Maintaining Cellular Homeostasis
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Maintaining Cellular Homeostasis
How do organisms regulate their body’s internal environment?
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Maintaining Cellular Homeostasis
• The cell membrane is selective – only allowing certain materials to pass through. It is comparable to a gatekeeper – controlling the traffic of substances passing in and out of the cell.
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Maintaining Cellular Homeostasis
• The cell membrane’s selective permeability is essential for maintaining cellular homeostasis – the steady state of operations inside the cell.
Plasma Membrane
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Maintaining Cellular Homeostasis
• The specific processes involved in the movement of substances in and out of the cell and thereby helping to maintain cellular homeostasis are listed below:– Diffusion– Facilitated diffusion– Osmosis– Active transport– Endocytosis– Exocytosis
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Maintaining Cellular Homeostasis
• Diffusion is the process by which molecules move from where they are greater in concentration to where they are lesser in concentration.
• The cell does not have to use any of its energy for this process. The molecules move by their own kinetic energy.
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lipid-soluble molecules(O2, CO2, H2O)
(extracellular fluid)
(cytoplasm)
Simple diffusion
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water molecule
drop of dye
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Maintaining Cellular Homeostasis
• Facilitated diffusion is the process in which substances move from greater to lesser concentration across the cell membrane with the assistance of carrier proteins.
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Maintaining Cellular Homeostasis
• Osmosis is the diffusion of water across a selectively permeable membrane.
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Figure 5.8 Osmosis Modifies the Shapes of Cells
Onion cell osmosis
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Maintaining Cellular Homeostasis
• Active Transport is the movement of a substance across a cell membrane against a concentration gradient; it requires the cell to expend energy.
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Maintaining Cellular Homeostasis
• Endocytosis is the process by which a cell surrounds and engulfs substances. It occurs in two forms: pinocytosis and phagocytosis.
• Pinocytosis is the type of endocytosis in which a cell engulfs fluids.
• Phagocytosis is the type of endocytosis in which a cell engulfs large particles or whole cells.
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Maintaining Cellular Homeostasis
• Exocytosis is the process in which a cell releases large molecules into the cell’s external environment. It works like this: a vesicle inside a cell fuses with the cell membrane and releases its contents to the external environment.
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Homeostasis
• Maintaining internal equilibrium