Chapter 4 Cells and Their Environment

1. Chapter 4 Cells and Their Environment

2. Section 4-1 • 1 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 waterdown its [ ] gradientthrough a selectively permeable membrane;type of passive transport where no ATP energy is needed

5. Section 4-1 • 3 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 ishypotonic sol’n • No net water movement: Sol’n that produces no ∆ in cell volume is isotonic sol’n Red Blood Cell isotonic hypertonic hypotonic

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