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Chapter 7: Membrane Structure and Function - Coggle Diagram
Chapter 7:
Membrane Structure and Function
7.1
Cellular membranes are fluid mosiacs of Lipids and proteins
Amphipathic
Having both a hydrophilic region and a hydrophobic region.
Fluid mosaic model
cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids.
Proteins
Proteins are essential molecules in living organisms, accounting for over 50% of the dry mass of most cells.
Transmembrane Proteins
A type of integral protein that spans the entire membrane.
Peripheral Proteins
A protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer.
Integral Proteins
A transmembrane protein spans the membrane with hydrophobic parts inside the lipid layer and hydrophilic parts exposed to water on one or both sides.
Lipids
Lipids are a diverse group of hydrophobic molecules,
Glycolipids
A lipid with one or more covalently attached carbohydrates.
7.2
Membrane structure results in selective permeability
Selective Permeability
A property of biological membranes that allows them to regulate the passage of substances across them.
Transport Proteins
A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.
Aquaporins
A channel protein in a cellular membrane that specifically facilitates osmosis, the diffusion of free water across the membrane.
7.3
Passive transport is diffusion of a substance across a membrane with no energy investment
Diffusion
The random thermal motion of particles of liquids, gases, or solids. In the presence of a concentration or electrochemical gradient, diffusion results in the net movement of a substance from a region where it is more concentrated to a region where it is less concentrated.
Concentration Gradient
A region along which the density of a chemical substance increases or decreases.
Osmosis
The diffusion of free water across a selectively permeable membrane.
Tonicity
The ability of a solution surrounding a cell to cause that cell to gain or lose water.
Isotonic
Referring to a solution that, when surrounding a cell, causes no net movement of water into or out of the cell.
Hypertonic
Referring to a solution that, when surrounding a cell, will cause the cell to lose water.
Hypotonic
Referring to a solution that, when surrounding a cell, will cause the cell to take up water.
Osmoregulation
Regulation of solute concentrations and water balance by a cell or organism.
Turgid
Very firm
Flaccid
Limp
Plasmolysis
A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.
Facilitated Diffusion
The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure.
Channels
Ion Channels
A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.
Gated Channels
A transmembrane protein channel that opens or closes in response to a particular stimulus.
7.4
Active transport uses energy to move solutes against their gradients
Active Transport
The movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and requiring an expenditure of energy.
Sodium-Potassium Pump
A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into 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.
Electrochemical Gradient
The diffusion gradient of an ion, which is 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.
Proton Pump
IAn 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.
Contransport
The coupling of the “downhill” diffusion of one substance to the “uphill” transport of another against its own concentration gradient.
7.5
Bulk transport across the plasma membrane occurs by exocytosis and endocytosis
Exocytosis
The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane.
Endocytosis
Cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane.