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Section 4-1 1 way cells maintain homeostasis is controlling movement of substances across cell membrane Cells must use energy to transport some substances.

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Presentation on theme: "Section 4-1 1 way cells maintain homeostasis is controlling movement of substances across cell membrane Cells must use energy to transport some substances."— Presentation transcript:

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2 Section way cells maintain homeostasis is controlling movement of substances across cell membrane Cells must use energy to transport some substances across cell membrane Other substances move across cell membrane w/out energy = Passive Transport

3 Section 4-1 Diffusion: Movement of sub from area of high [ ] to area of low [ ] by random motion of particles Many substances enter/leave cells by diffusing across cell membrane

4 Section 4-1 Osmosis: Diffusion of water down its [ ] gradient through a selectively permeable membrane; type of passive transport where no ATP energy is needed

5 Section possible directions of water movement: Water moves out : Water diffuses out of cell, cell shrinks; sol’n that causes cell to shrink is hypertonic sol’n Water moves in : Water diffuses into cell, cell swells; sol’n that causes cell to swell is hypotonic sol’n No net water movement : Sol’n that produces no ∆ in cell volume is isotonic sol’n isotonichypertonichypotonic Red Blood Cell

6 Section 4-1 Diffusion Through Ion Channels Protein Ion Channel: protein channel through which ions can cross cell’s membrane

7 Section 4-1 Facilitated Diffusion Carrier proteins: Bind to a specific substance on 1 side of membrane and carry sub across cell mem (Facilitated diffusion) and release it on the other side; no ATP energy needed

8 Section 4-2 Active Transport: Transport sub across cell mem against its [ ] gradient; uses ATP energy

9 Section 4-2 Sodium-Potassium Pump: Important carrier protein mem pump; transports 3 Na + out of cell and 2 K + into cell; uses ATP; important for nerve/muscle cell functioning

10 Section 4-2 Substances, proteins/polysaccharides, are too large to be transported by carrier proteins; so, moved across cell mem by vesicles Endocytosis: Movement of sub into cell by vesicle Exocytosis: Movement of sub out of cell by vesicle

11 Section 4-2 Receptor proteins: protein binds to specific signal molecule, enables cell to respond to a signal molecule


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