Chapter 3b Cells Membrane transport - Student Notes

Transcription

1 Chapter 3b Cells Membrane transport - Student Notes 1 Transport are permeable Some molecules the membrane; others do 2 Types of Membrane Transport processes No cellular required Substance its processes Energy required Occurs only in cell membranes 3 Passive Processes What determines whether or not a substance can passively permeate a membrane? of substance Channels of appropriate Carrier proteins 4 Processes Simple 1

2 mediated diffusion -mediated diffusion 5 Passive Processes: Simple Diffusion lipid-soluble (hydrophobic) substances diffuse directly through the bilayer 6 Fig. 3.7a, Pg Passive Processes: Diffusion Certain molecules (e.g., glucose, amino acids, and ions) use proteins or proteins, both of which: Exhibit (selectivity) Are saturable; rate is determined by of carriers or channels Can be regulated in terms of and 8 Diffusion Using Proteins integral proteins transport specific (e.g., sugars and amino acids) Binding of substrate causes in carrier 9 Fig. 3.7, pg Facilitated Diffusion Using channels formed by transmembrane proteins selectively transport or 2

3 Two types: channels Always open channels 11 Fig. 3.7c, Pg. 69 Controlled by chemical or electrical 12 Passive Processes: Movement of solvent (water) across a selectively permeable membrane Water diffuses through plasma membranes: Through the Through water channels called (AQPs) 13 Fig. 3.7d, pg Passive Processes: Osmosis Water concentration is determined by because solute particles displace water molecules : The measure of total concentration of particles When solutions of different osmolarity are by a, osmosis occurs until is reached 15 Fig. 3.8, pg Fig. 3.8b pg Importance of Osmosis 3

4 When osmosis occurs, water or a cell in cell disrupts cell 18 Tonicity : The ability of a solution to cause a cell to or : A solution with the same as that of the : A solution having solute than that of the cytosol : A solution having solute concentration than that of the 19 Fig. 3.9, pg Summary of Passive Processes Also see Table Membrane Transport: Active Processes Two types of processes: transport transport Both use to solutes across a living plasma 22 Active Transport Requires (solute pumps) a concentration 4

5 Types of active transport: active transport active transport 23 Primary Active Transport Energy from of causes in transport protein so that bound solutes (ions) are across the membrane 24 Primary Active Transport (Na + -K + ATPase) Located in plasma membranes Involved in primary and secondary of and ions Maintains gradients essential for functions of and tissues 25 Fig. 3.10, pg Fig. 3.10, pg Secondary Active Transport Depends on an gradient created by primary transport stored in ionic is used indirectly to drive transport of 34 Secondary Active Transport 5

6 always transports more than substance at a time system: substances transported in direction system: substances transported in directions 35 Fig. 3.11, pg Fig. 3.10, pg Fig. 3.10, pg Transport Transport of particles,, and fluids across plasma membranes Requires cellular (e.g., ATP) 39 Vesicular Transport Functions: transport of cell transport cell transport, across, and then of cell - Into, & back out, (vesicular) trafficking transport from area or organelle in cell to 40 Endocytosis and Transcytosis Involve formation of often containing bulk /macromolecules 6

7 Often receptor mediated, therefore very selective 41 Fig. 3.12, pg Fig. 3.12, pg Endocytosis engulf solids and bring them into cell s and some 49 Fig.13.3b, pg Endocytosis phase endocytosis ( ) plasma membrane infolds, bringing extracellular fluid and solutes into interior of the cell - absorption in the small intestine 51 Fig.13.3b, pg Endocytosis? endocytosis clathrin-coated pits provide main route for endocytosis and transcytosis Uptake of (think processing) low-density lipoproteins, iron, and insulin 53 Fig.13.3c, pg Exocytosis Examples: 7

8 secretion release!!!! secretion Ejection of 55 Fig. 3.14a, pg Summary of Active Processes 8