Questions Describe how the cell membrane helps maintain homeostasis. Explain what affect more cholesterol would have on the cell membrane. Explain what the proteins in the cell membrane do. 1

Explain how the cell membrane helps maintain homeostasis. Agenda for Thursday Nov 19 th 1.Quiz 2.Start Gummy bear lab 3.Diffusion/osmosis notes 2

Vocab Solute – stuff we want to dissolve Solvent – substance in which something dissolves Concentration – amount of a solute dissolved in a given volume of solution – A lot = concentrated – A little = dilute 3

Passive transport No energy needed Particles move from high concentration to low concentration Particles flow until equilibrium is reached – No change in concentration on each side Diffusion = particles moving across membrane Osmosis = water moving across membrane 4

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Diffusion and Membrane Membrane has selective permeability – Polar/nonpolar regions on lipid bilayer Cannot pass through: Ions (salts dissolved in water) Hydrophilic molecules (glucose) Macromolecules 6

Facilitated Diffusion Protein in membrane move particles across 7

Facilitated Diffusion Carrier proteins – Change shape 8

Osmosis Diffusion of water across membrane 9

What is wrong with the cartoon? Agenda for Friday Nov 20 th 1.Go over cell worksheets 2.Finish gummy bear lab 3.Finish notes 4.Osmosis practice sheet Test Tuesday 10

Osmosis Isotonic – concentration of solute is the same inside and outside cell – Water enters and leaves at same rate 11

Osmosis Hypotonic – concentration of solute is greater inside the cell, more water outside cell – Cells gain water – Animal cells can burst – Cell wall prevents plant cells from rupturing Turgor pressure supports the cell A cell under pressure is turgid 12

Osmosis Hypertonic – concentration of solute is greater outside the cell – Cells lose water – Animal cells shrivel up – Plants: membranes pulls away from the cell wall The cell wall is rigid and does not shrink 13

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Active Transport Substances moving from low to high concentrations – Need energy Use proteins in membrane 15

Na/K ATPase Pump Found in animal cells Helps maintain levels of sodium and potassium Uses energy (ATP) to move 3 Na ions out of the cell and 2 K into the cell High levels of sodium on outside creates a gradient 16

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Coupled Transport Linked, simultaneous transport of two substances across a cell membrane Create a high concentration gradient on 1 side – Protein channels open & allow other particles (sucrose/sugar) to move across membrane – Spend very little energy 18

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Transport of Large Particles Endocytosis – brings substance into cell 20

Transport of Large Particles Exocytosis – expels stuff from cell – waste, substances (hormones) produced by cell 21

In passive transport, particles move from what to what concentration? Agenda for Monday Nov 23 rd 1.Go over homework 2.Go over lab 3.Review stuff 22