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Chapter 7: Membrane Structure and Function - Coggle Diagram
Chapter 7: Membrane Structure and Function
Cell Transportation
Passive Transportation
Diffusion of a substance across a membrane with no energy investment
Doesn't Require ATP
Moves down the concentration gradient
Concentration Gradient
A region along which the density of a chemical substance increase or decreases
Each substance diffuses down its own gradient
They're unaffected by other substances concentration gradients
Represents potential energy
Diffusion
The movement of molecules from high to low solute concentration
Semi-Permeable Membrane
Has different effects on the rates of diffusion of various molecules
Allows small, uncharged, and nonpolar molecules through
Driven by the random thermal motion of molecules
Facilitated Diffusion
The movement of water from low to high solute concentration but, with the help of various movements
Carrier Proteins
Provide corridors that allow specific molecules or ions to cross the membrane
Hydrophilic Passage
Allows water molecules or small ions to diffuse quickly from one side to another
Channel Proteins
Undergo a subtle change in shape that somehow translocates the solute-binding site across the membrane
Also known as Ion channels
Osmosis
The movement of water from low to high solute concentration
Requires a semi-permeable membrane
Water always follows the higher concentration of solute
Tonicity
The measure of osmosis
The ability of a solution surrounding a cell to cause that cell to gain or lose water
Hypotonic
Refers to a solution that, when surrounding a cell, will cause the cell to take up water
Water diffuses across the membrane but, it's entering the cell faster than it's entering the cell
The cell swells
Animal Cell
Hypotonic environment makes an animal cell lysed
Plant Cell
Hypotonic environment keeps a plant cell stable
Known as a turgid plant cell
Isotonic
Refers to a solution that, when surrounding a cell causes no net movement of water into or out of the cell
Water diffuses across the membrane but, at the same rate both in and out
Animal Cell
Isotonic environment keeps animal cells stable
Known as a normal animal cell
Plant Cell
Isotonic environment makes a plant cell flaccid
Hypertonic
Refers to a solution that, when surrounding a cell, will cause for the cell to lose water
Water diffuses across the membrane but, it's leaving the cell faster than it's entering the cell
The cell shrivels
Animal Cell
Hypertonic environment makes an animal cell shriveled
Plant Cell
Hypertonic environment makes a plant cell plasmolyzed
Osmoregulation
Regulation of solute concentrations and water balance by a cell or organism
Organisms that lack cell walls must have other adaptations
Aquaporins
Water channel proteins
Facilitate the massive levels of diffusion of water that occur in plant cells and animal cells
Active Transportation
Uses energy to move solutes against their gradients
Requires ATP
The movement of molecules from low to high concentration
Moves against the concentration gradient
Sodium-Potassium Pump
A transportation protein in the plasma membrane of animal cells that actively transport sodium out of the cell and potassium into the cell
Endocytosis
Takes substances into the cell
Phagocytosis
The cell is eating (solids)
Pinocytosis
The cell is drinking
Exocytosis
Takes substances out of the cell
Membrane Potential
The difference in electrical charge (voltage) across a cell’s plasma membrane due to the differential distribution of ions
Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances
Ranges from about -50 to -200 millivolts (mV)
Electrochemical Gradient
The diffusion gradient of an ion
Affected by both the concentration difference of an ion across a membrane (a chemical force) and the ion’s tendency to move relative to the membrane potential (an electrical force)
Electrogenic Pump
An active transport protein that generates voltage across a membrane while pumping ions
Stores energy that can be used for cellular work
Proton Pump
An active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process.
Cotransport
The coupling of the “downhill” diffusion of one substance to the “uphill” transport of another against its own concentration gradient.
When active transport of a solute, indirectly drives transport of other substances
Cellular Membrane
Fluid mosaics of lipids and proteins
Structure
Lipids and Proteins are staple ingredients of membrane
Most abundant lipids are Phospholipids
Phospholipids are amphipathic molecules, containing hydrophobic and hydrophilic regions
Most membrane proteins are also amphipathic
Integral Proteins
Penetrate the hydrophobic interior of the lipid bilayer
Transmembrane Proteins
Other integral proteins extend only partway into the hydrophobic interior
Peripheral Proteins
Are loosely bound to the surface of the membrane, often to exposed parts of integral proteins
Functions
Proteins are responsible for transportation, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton/extracellular membrane
Carbohydrates are also important
In the cell membrane, used for cell to cell recognition
Cell-cell recognition
A cell’s ability to distinguish one type of neighboring cell from another
Covalent Bonds
Glycolipids
A lipid with one or more covalently attached carbohydrates
Glycoproteins
A protein with one or more covalently attached carbohydrates
Fluid Mosaic Model
The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids
Fluidity of Molecules
A membrane remains fluid as temperature decreases until the phospholipids settle into a closely packed arrangement and the membrane solidifies
Membranes rich in unsaturated fatty acids and cholesterol are more fluid than rich in saturated fatty acids
Membranes must be fluid to work properly
Fluidity affects both the permeability and the ability of membrane proteins to move where their function is needed
When a membrane solidifies, its permeability changes, and enzymatic proteins in the membrane may become inactive if their activity requires movement within the membrane
Membranes that are too fluid cannot support protein function either