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| The cell, or plasma, membrane allows some materials to cross it more easily than others. Ex: water passes more easily than Glucose. |
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| A molecule having both a hydrophobic, or water "fearing", portion AND a hydrophillic, or water "loving", part. |
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| A membrane made up of a lipid bilayer with attached and/or imbeddded proteins. |
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| Plasma membrane proteins which penetrate or completely span the phospholipid bilayer. |
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| Proteins loosely bound to the surface of the bilayer. Can be part of an integral protein. |
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| The six kinds of membrane proteins |
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Definition
| 1. Transport; 2. Enzymatic; 3. Signal Transduction; 4. Cell-Cell Recognition; 5. Intercellular Joining; 6. Attachment |
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| Spans the membrane, may provide a hydrophillic channel, may change shape to transport material or may hydrolyze ATP as an energy source to actively pump materials into/out of the cell. |
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| Active site may be on the outside of the cell which is triggered by substances in the ECM. Can also have several enzymes near each other that work together. |
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| May have a binding site into which a specific chemical fits outside the cell which then causes a reaction inside the cell. |
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| Done with glycoproteins on the surface of the cell attached to proteins which identify that cell to other cells. |
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Definition
| Proteins on adjacent cells hook together, briefly, for cell interaction/sharing. |
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| Attachment to the cytoskeleton and ECM |
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Definition
| When attached to the cytoskeleton, it may act to further help maintain cell shape and may stabilize protein location in the membrane. Proteins that adhere to the ECM can coordinate extra and intracellular changes. |
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Definition
| Usually short, branched chains of 15 or fewer sugar units. |
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Definition
| When short, branched carbohydrates are bonded to lipids as in the plasma membrane |
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Definition
| When short, branched carbohydrates are covalently bonded to membrane proteins. |
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Definition
| The glycoproteins on the outer surface of cells are unique to species, individuals and even different cells within an individual. Ex: blood types are realted to variations in the glycoproteins on RBC's. |
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Definition
| Membranes have distinct inside and outside faces. Vessicles fuse with the plasma membrane. Molecules that start on the inside face of the ER end up on the outside face of the plasma membrane. |
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Definition
| Transport proteins which span the plasma membrane. They function by having a hydrophilic tunnel for polar molecules or ions can travel thru. |
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Definition
| A specific channel protein which facilitates water transport across the cell membrane. |
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Definition
| Transport proteins that change shape and hold onto their passengers as they cross the palsma membrane. Substance specific. |
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Definition
| Caused by the molecular energy called thermal motion. The tendency for molecules of any substance to spread out evenly into the available space. |
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Definition
| Once a solution is isotonic, and is in equalibrium, molecules continue to move back and forth across the membrane. They just do it equally. |
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| An area of with a higher, or greater, concentration of a solute. |
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| An area with a lower, or lesser, concentration of a solute. |
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| In passive diffusion molecules travel from the area of higher concentration to an area of lower concentration or down its concentration gradient. This requires no work, or energy expendature, by the cell. Each substance has its own gradient and it is unaffected by the gradient of other substances. Has potential energy. |
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Definition
| Diffusion of a substance across a membrane which requires no energy expendature by the cell. |
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Definition
| The diffusion of water across a selectively permeable membrane. Creates a balance of water between the inside of the cell and its environment. |
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Definition
| The ability of a solution to cause a cell to gain or lose water. |
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| When the concentration of water and/or a given solute is the same both inside and outside the cell. There is no net movement occuring. |
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| Adaptations for maintaining control over water balance between a cells interior and exterior environments. Ex: Paramecium has a membrane less permeable to water than most cells and it has a contractile vacuole to prevent the cell over filling with water. |
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Definition
| "very firm" which is the healthy state for plant cells. |
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Definition
| "limp" or when a plant cell cannot maintain tugidity (the healthy level of firmness in a plant cell) |
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Definition
| When the plant cells membrane pulls away from the cell wall because the cell is in a hypertonic solution and too much water leaves the cell. Causes the cell to wilt and can be lethal. |
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Definition
| How transport proteins help hydrophlilic molecules and ions cross the hydrophobic bilayer without the cell expending any energy. The exact process is still unclear. |
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| A kind of gated channel which "opens" or "closes" based on the needs of the cell. It is controlled by some stimulus which may be chemical or electrical. |
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| Transport which requires energy to be expended by the cell, usually in the form of ATP. Allows the cell to maintain solute concentrations against the concentration gradient. |
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| A form of active transport which requires energy. A transport protein which exchanges sodium for potassium across the membrane. |
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Definition
| The in side of a cell is more negatively charged than is the outside of the cell. This difference in charge creates a voltage of -50 to -200 millivolts across the membrane. The minus sign indicates the inside is the more negative side. |
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Definition
| How ions move across the membrane. This movement goes down both the concentration gradient and the electrical gradient. Ex: Nerve cells |
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| A transport protein that generates a voltage across a membrane. Ex: Sodium Potassium pump in animal cells. |
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| The main electrogenic pump in plant, fungi and bacteria. It actively transports hydrogen ions across the membrane. |
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Definition
| A single ATP-powered pump that transports a specific solute can indirectly drive the active transport of several other solutes. Ex: a plant cells proton pump creates a gradient of H+ ions which then go back across the membrane and drive the active transport of amino acids, sugars, etc. |
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| When the cell exports or secretes macromolecules by the fusion of vessicles with the plasma membrane. Ex: pancreatic cells excrete insulin, neurons excrete nuerotransmitters. |
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| When the cell takes in macromolecules and particulate matter by forming new vessicles from the plasma membrane. The reverse of exocytosis. |
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| Any molecule that binds specifically to a receptor site of another molecule. LDL receptor proteins. |
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