Homeostasis and Cell Transport

1. Homeostasis and Cell Transport Chapter 5

2. “Passive Transport” • Crossing cell membrane using NO energy. EXAMPLES: • Diffusion • Osmosis • Facilitated Diffusion • Diffusion through ion channels

3. Diffusion • Movement of molecules from an area of higher concentration to an area of lower concentration. • Concentration gradient: the difference in the concentration of molecules across a distance

4. Diffusion Diffusion is driven entirely by the molecules’ kinetic energy. Moving “down the concentration gradient.”

5. Diffusion • Equilibrium- the concentration of molecules will be the same throughout

6. Osmosis • The process by which water molecules diffuse across a cell membrane from an area of higher concentration to an area of lower concentration • Does not require energy

8. Osmosis • Hypo- : under • Hyper-: over • -tonic : solute (I say “salty”) • Iso-: same or equal • Review: solute + solvent = solution • Net direction depends on relative concentration of solutes on the two sides of the membrane.

9. Directions of Osmosis Hypotonic solution- The solution has lower concentration of solute

10. Directions of Osmosis Hypertonic solution- the solution has a higher concentration

11. Directions of Osmosis Isotonic solution- Concentrations are equal

12. How Cells Deal with Osmosis Contractile vacuoles- pump water out of cells, uses energy, maintain homeostasis

13. How Cells Deal with Osmosis • Turgor pressure- pressure that water molecules exert against the cell wall • Plasmolysis- loss of turgor pressure, plants wilts • Cytolysis- bursting of cells

15. FACILITATED DIFFUSION • Process used for molecules that cannot readily diffuse through cell membrane • Carrier proteins- assist molecules across membrane; each carrier is SPECIFIC for its molecule

17. FACILITATED DIFFUSION • Change shape when combined with molecule • (HL): no energy used • example: Glucose

18. ION CHANNELS • Ions are not soluble in lipid • Proteins provide small passageways across membrane • Move ions (atoms with charge + or -) • (HL)

19. ION CHANNELS • Channel is SPECIFIC for ion • Example: Ca+2 ion channel • Some are always open • Some are gated and open with a stimulus • Stimuli examples: (stretch, electrical, chemical)

20. Active Transport Move materials from an area of lower concentration to an area of higher concentration, or “up” their concentration gradient

21. Active Transport • Crossing cell membrane using energy. • Driven by chemical or ATP energy. • Always from Low concentration to High (LH) • Moving “up the concentration gradient.”

22. Active Transport • Example: Sodium-Potassium Pump (Na+-K+pump)

23. MOVEMENT IN VESICLES • Endo- and Exocytosis • Endo- means “into” • Exo- means “to exit” • -cytosis: “the cell”

24. Endocytosis “Gulping food” Importing “Large packages of lots of small stuff” Pinocytosis: fluid “sipping” Phagocytosis: large particles or whole cells “gulping” .

25. Exocytosis: Exporting substances OUT OF the cell Used to eject: protein products of the cell waste products toxins