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. Many substances enter/leave cells by diffusing across cell membrane
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. 3 possible directions of water movement:
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 is hypotonic 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. Diffusion Through Ion Channels Protein Ion Channel:
Section 4-1
Diffusion Through Ion Channels
Protein Ion Channel:
protein channel through which ions can cross cell’s membrane

7. Facilitated Diffusion Carrier proteins:
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. Sodium-Potassium Pump:
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. Movement of sub into cell by vesicle Exocytosis:
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