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# Membrane Dynamics

### Week 3

What is osmosis? Diffusion of water across a membrane from areas of increased concentration to an area of decreased concentration
Explain the concept of osmosis 2 compartments separated by a membrane that is permeable to water but not to glucose. So water is able to move from membrane but not glucose. Water moves by osmosis to a more concentrated solution.
Comparing osmolarities solutions with same conc: isometric. solution 1 with greater conc than solution 2: 1 hyper osmotic to 2 . Solution 1 conc less than solution 2: 1 hyposmotic to2.
What is tonicity? Increased tonicity means? Tonicity describes the volume change of a cell at equilibrium. INCREASED tonicity, INC concentration of solutes DECREASED conc of water
When the cell in the solution swells solution is hypotonic
When the cell doesn't change size solution is isotonic
When cell shrinks solution is hypertonic
What is bulk flow? Explain. Bulk flow is the most general form of biological transport. Both gases & liquids are fluids. In bulk flow, a pressure gradient causes fluid to flow from regions of higher pressure to regions of lower pressure.
Passive vs. Active Transport Passive: does not require the input of energy. Active: requires the input of energy from some outside source such as ATP
Define Diffusion The movement of molecules from an area of higher concentration to an area of lower concentration
Properties of Diffusion (7) Passive process, high conc to low conc, net movement until conc is equal, rapid over short distances, directly related to temperature, inversely related to molecular weight size, in open system or across a portion
Homeostasis Does not mean equilibrium. Body has 2 distinct fluid compartments: the cells & fluid that surrounds the cell.
Cell membrane Acts as a barrier to create distinct intracellular & extracellular compartments. Although the contents in compartments differ, homeostasis keeps it in a dynamic steady state
4 Categories of Membrane Proteins (Protein Mediated Transport) Structural proteins, Enzymes, Membrane receptor proteins, Transporters (channel + carrier proteins)
What is Protein-Mediated Transport? A process which involves solutes crossing membranes with the help of membrane proteins.
Channel Proteins They form open, water-filled passageways. Classified according whether their gates are open or closed. Open-> gates open allowing ions to move back & forth w/o regulation. Gated--> closed state mostly
What controls the opening & closing of gated channels? Chemically gated channels: controlled by intracellular messenger molecules/extracellular ligands that bind to channel protein. Voltage gated channels: according to electrical state of cell changing. Mechanically gated channels: respond to physical forces
Carrier Proteins 2nd type of transport protein. Change conformation to move molecules. Facilitated diffusion uses carrier proteins. move solutes in & out of cells
Why are movements of materials between & within compartments necessary and how is it accomplished? It is necessary for communication and is accomplished by mass law and biological transport.
What happens in mediated transport for the process to be known as facilitated diffusion? Transport is passive & moves molecules down their concentration gradient & if net transport stops when concentrations are equal on both sides of the membrane.
What happens in mediated transport for the process to be known as active transport? If protein-mediated transport requires energy from ATP/ other outside source & moves substance against its concentration gradient
What do structural proteins do? Maintain cell shape & form cell junctions
What do membrane-associated enzymes do? Catalyse chemical reactions & help transfer signals across the membrane
What are receptor proteins? They are a part of the body's signalling system
What do transport proteins do? They move many molecules into or out of the cell
Created by: meunid

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