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.

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Explain how the cell membrane helps maintain homeostasis.

Agenda for Thursday Nov 19th 1.Quiz2.Start Gummy bear lab3.Diffusion/osmosis notes

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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

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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

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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

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Facilitated Diffusion

• Protein in membrane move particles across

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Facilitated Diffusion

• Carrier proteins – Change shape

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Osmosis• Diffusion of water across membrane

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What is wrong with the cartoon?

Agenda for Friday Nov 20th 1.Go over cell worksheets2.Finish gummy bear lab3.Finish notes4.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

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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

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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

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Active Transport

• Substances moving from low to high concentrations– Need energy

• Use proteins in membrane

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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 gradient16

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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

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Transport of Large ParticlesEndocytosis –brings substance into cell

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

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In passive transport, particles move from what to what

concentration?

Agenda for Monday Nov 23rd 1.Go over homework2.Go over lab3.Review stuff

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