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54 Cards in this Set
- Front
- Back
Plasma Membrane Functions |
- provides physical isolation from the extracellular fluid, so that the cytoplasm is kept different from extracellular fluid - controls molecules that enter and exit the cell - has receptors that allow the cell to recognize molecules and other cells in the surrounding environment |
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Structure of the plasma membrane is described by what model? |
Fluid Mosaic Model |
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What is the plasma membrane composed of? |
Lipids and Proteins |
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Bilayer of phospholipids |
The basic component of the plasma membrane |
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What does bilayer mean? |
That the phospholipids lie in two distinct layers |
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Hydrophilic |
Polar heads: water-loving |
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Hydrophobic |
Non-polar tails: water-hating |
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What's inserted in the phospholipid bilayer? |
Cholesterol Molecules |
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What keeps the membrane fluid and flexible? |
Phospholipid and Cholesterol Molecules |
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What does cholesterol prevent? |
Close packing of phospholipids at low temperatures |
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Transmembrane Proteins |
some proteins span through the width of the membrane |
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Surface Proteins |
Other proteins are partially embedded on the inside or on the outside of the membrane |
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2 arrangements of proteins associated with plasma membrane |
Transmembrane Proteins & Surface Proteins |
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3 types of proteins in the plasma membrane |
Receptor Proteins, Channel Proteins, Carrier Proteins |
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Receptor Proteins |
Allow specific extracellular molecules to bind them and trigger a response (a change) in the cell's activity |
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Channel Proteins |
Form a channel (a pore) that allows water, ions, and other solutes to travel through the membrane, bypassing its lipid portion |
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Carrier Proteins |
Different from channel proteins as they first bind and then transport solutes across the plasma membrane. Change shape as the molecule binds to them and open toward the other side of the cell and release the molecule |
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Where are carbohydrates found? |
Outer surface of the membrane |
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Cell-to-cell identification |
Prevents the immune system from attacking the body's own cells and tissues - Glycoproteins, Gylcolipids |
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Permeability |
the "leakiness" of the plasma membrane. reflects the ease with which dissolved materials can cross the plasma membrane |
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What are the factors that affect whether a molecule can cross a membrane? |
Size & shape, electric charge, & lipid solubility |
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What does passive force use? |
Concentration gradient for substance to transport it. Moves it from higher to lower concentration. moving the substance down |
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What does active force use? |
Uses ATP as an energy source to transport the substance. Moves from lower to higher. Moves up 'against' the concentration gradient |
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Passive Transport |
Any type of transport that uses passive force |
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Active Transport |
Any type of transport that uses the active force |
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Kinds of Passive Transport |
Diffusion, Osmosis, Facilitated Diffusion |
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Kinds of Active Transport |
Active transport (solute pumping), Vesicular Transport (Endocytosis and exocytosis) |
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What do all solutions contain? |
A solute (solid) and a solvent (liquid) |
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What happens when a solute is mixed with a solvent? |
The molecules move randomly and take up available space |
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What is diffusion? |
The movement of solute molecules from an area of higher to lower concentration; DOWN the concentration gradient |
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What can lipid soluble molecules do? |
Diffuse through the plasma membrane easily as they are able to diffuse through the lipid portions of the membrane |
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What do ion and water soluble substances do? |
They're not lipid soluble so they must pass through the membrane channels to enter the cytoplasm |
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What is an example of diffusion in the body? |
Transport of respiratory gases between the lungs and blood |
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What is osmosis? |
Diffusion of water (solvent) across a selectively permeable membrane. Occurs from higher to lower concentration of water |
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Three Characteristics of Osmosis |
1. Diffusion of water molecules across a selectively permeable membrane 2. Occurs across a selectively permeable membrane that is freely permeable to water, but not freely permeable to all solutes 3. Water flows from low solute concentration to high solute concentration |
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Osmotic Pressure |
The force with which pure water moves into a solution as a result of its solute concentration |
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What happens when the concentration of solutes is higher in a solution? |
The higher its osmotic pressure is |
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Tonicity |
The ability of an extracellular solution to cause a cell to gain or lose water; based on the concentration of solutes |
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Hypertonic Solution |
Solution with higher solutes |
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Hypotonic Solution |
Solution with lower solutes |
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Isotonic Solution |
If solutes are equal in both solutions |
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When does osmosis always occur? |
From a hypotonic to a hypertonic solution |
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2 types of carrier-mediated transport processes |
Facilitated Diffusion & Active Transport |
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What do membrane proteins bind to? |
Specific ions and molecules and carry them across the membrane |
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What can carrier mediated transport processes be? |
Passive (no ATP required) or Active (ATP dependent) |
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What does facilitated diffusion use? |
Carrier proteins to passively move larger molecules, like glucose and amino acids down their concentration gradient. Insoluble in lipids and too large to pass through membrane channels |
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What does an exchange pump do? |
Move two ions in opposite direction. Ex. sodium-potassium exchange pump |
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Active transport always involves carrier protein called what? |
Pump |
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Vesicular Transport |
Moves substances either into or out of cell in small membrane sacs called vesicles |
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What does vesicular transport require? |
Energy from ATP |
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2 major categories of vesicular transport |
1. Endocytosis: vesicles enter into cells 2. Exocytosis: vesicles exit the cells |
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What does endocytosis involve? |
The packaging of extracellular materials in a vesicle at the cell surface for import into the cell |
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3 major types of endocytosis |
1. Receptor-mediated Endocytosis: molecules bind to receptors on the surface, and the membrane pinches off to for a vesicle 2. Pinocytosis: 'cell drinking; is the formation of vesicles filled with fluid 3. Phagocytosis: 'cell eating' is the formation of vesicles containing large particulate matter |
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How does exocytosis occur? |
The reverse of endocytosis 1. Vesicles form inside the cell and travel to the plasma membrane 2. The membrane of the vesicle fuses with the plasma membrane of the cell 3. The membrane ruptures and contents of the vesicle are released outside the cell |