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Definition
1. Isolate cell content from the external environment
2. Regulate the exchange of essential substances
3. Allow communications between cells
4. Create attachments in and between cells
5. Regulate biochemical reactions |
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| Phospholipids form a bilayer with hydrophilic heads and hydrophobic tails (with more saturated phospholipids are more fluid) (with more cholesterol are less fluid) |
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| May be attached to membrane by a hydrophobic group. May be embedded in membrane. Many are glycoproteins (protein with a carbohydrate attached. |
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| Receive and respond to messages from outside the cell |
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| Glycoproteins with carbohydrates, on the outside of the membrane, cell specific |
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| Promote chemical reactions |
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| Anchored to cytoskeleton or extra cellular matrix or to other cells |
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Definition
1. Channel proteins = form a channel/ pore that selectively allows molecules to get through
2. carrier proteins = bind to and carry molecules across the membrane |
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| Cell membranes are viewed as two-dimensional solutions of oriented globular proteins and lipids |
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| Two Types = passive transport and energy-requiring transport |
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Definition
Diffusion of molecules or ions across membrane down a concentration gradient (high>low)
-Simple diffusion
-Facilitated diffusion
-Osmosis |
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Definition
| Very small molecules with no net charge |
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Hydrophilic molecules (ions/polar molecules)
Channel proteins - selectivity for shape and charge of what they allow through the pore
Carrier protein - endose protein to allow to go through / can change its shape to allow different proteins through |
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Definition
| Diffusion of water across a selectively permeable membrane from a high concentration gradient to low (simple diffusion/facilitated by aquaporin channels) |
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| Energy-Requiring Transport |
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Definition
Movement of molecules or ions across membrane agains concentration gradient (low>high)
1. Active Transport
2. Endocytosis
3. Exocytosis |
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Definition
| Requires a protein that spans the membrane, a binding site specific to the molecule, and a binding site for energy carrier such as ATP |
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Definition
Engulfed by membrane into the cell.
-Pinocytosis = liquids into cell
-Receptor-mediated endocytosis = receptor based molecules into cell
-Phagocytosis = engulfing large particles |
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Definition
Out of the cell.
Membrane bound vesicles fused with a plasma membrane. |
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