Cell Boundaries Part 2


Published on

part 2 of cell boundary notes

Published in: Technology, Business
1 Like
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Cell Boundaries Part 2

  1. 1. What happens when we reach equilibrium? <ul><li>Particles continue moving across membrane but in both directions! ***No more changes in concentration </li></ul>
  2. 2. Problems for diffusion… <ul><li>Things too large </li></ul><ul><li>Charged molecules </li></ul><ul><ul><li>Positive/negative </li></ul></ul><ul><ul><li>Opposites attract but likes do not… </li></ul></ul><ul><ul><li>These all present serious problems for things getting across membranes… </li></ul></ul>
  3. 3. If things can cross a membrane we call the membrane PERMEABLE If things canNOT cross a membrane we call the membrane IMPERMEABLE
  4. 4. Biological membranes are… <ul><li>SEMI-PERMEABLE </li></ul><ul><li>Aka… </li></ul><ul><li>Selectively permeable </li></ul><ul><li>Cell membranes are picky </li></ul>
  5. 5. Osmosis <ul><li>Water (H2O) can pass easily through most biological membranes </li></ul><ul><li>Def: </li></ul><ul><ul><li>Diffusion of Water through a semi-permeable membrane </li></ul></ul>
  6. 6. How Osmosis works… <ul><li>We have water molecules and some other molecules, let’s say sugar </li></ul><ul><li>If we have more water on one side of the membrane (HIGH conc. of H2O), then the water will diffuse across… </li></ul><ul><li>Membrane will let water thru but not sugar </li></ul><ul><li>Water can move back and forth (not sugar) </li></ul>
  7. 7. Water moves from areas of HIGH conc. To areas of LOW conc. <ul><li>Water moves across till equilibrium is reached </li></ul><ul><li>Isotonic: </li></ul><ul><ul><li>when conc. of water = conc. of sugar </li></ul></ul><ul><li>Hypertonic: “above strength” </li></ul><ul><ul><li>When we begin with more sugar in water </li></ul></ul><ul><ul><li>More concentrated sugar solution on side A </li></ul></ul><ul><li>Hypotonic: “below strength” </li></ul><ul><ul><li>When we end with less sugar </li></ul></ul><ul><ul><li>Dilute sugar solution on side A </li></ul></ul>
  8. 9. Osmotic Pressure <ul><li>We will discuss later… </li></ul><ul><ul><li>PLEASE read page 186 </li></ul></ul><ul><ul><li>This is a confusing concept… </li></ul></ul>
  9. 10. How do big molecules diffuse across a membrane so quickly if the membrane is selectively permeable?
  10. 11. Facilitated Diffusion <ul><li>What does facilitate mean? </li></ul><ul><li>Proteins are the extra help </li></ul><ul><li>“escorts” across the membrane </li></ul><ul><li>We call these protein channels… </li></ul><ul><ul><li>Allow specific things thru </li></ul></ul>
  11. 12. Facilitated Diffusion (continued) <ul><li>FAST </li></ul><ul><li>SPECIFIC </li></ul><ul><li>Still diffusion so we only see it from high concentration to low </li></ul><ul><li>Does NOT require energy </li></ul>
  12. 15. What about when we want to go against the concentration? (From low concentration to high?)
  13. 16. What do we need??? <ul><li>ENERGY!!!! </li></ul>
  14. 17. ACTIVE transport <ul><li>Process that moves molecules against the concentration gradient </li></ul><ul><li>Requires ENERGY </li></ul><ul><li>A protein pumps small molecules and ions across a cell membrane against the conc. gradient </li></ul><ul><li>To pump large molecules and clumps… </li></ul><ul><ul><li>2 other processes: </li></ul></ul><ul><ul><ul><li>Exocytosis </li></ul></ul></ul><ul><ul><ul><li>Endocytosis </li></ul></ul></ul><ul><ul><ul><li>The can change shape of membrane </li></ul></ul></ul>
  15. 18. Types of Active transport <ul><li>Molecular Transport </li></ul><ul><ul><li>When small ions and molecules are carried across membrane </li></ul></ul><ul><li>Endocytosis </li></ul><ul><ul><li>Endo- means…. </li></ul></ul><ul><ul><li>-Cyto- means… </li></ul></ul><ul><ul><li>-sis mean…. </li></ul></ul><ul><li>Exocytosis </li></ul><ul><ul><li>Exo- means…. </li></ul></ul><ul><ul><li>-Cyto- means… </li></ul></ul><ul><ul><li>-sis mean…. </li></ul></ul>
  16. 19. Molecular Transport <ul><li>Proteins are used to pump small molecules and ions across membrane even against the conc. Gradient </li></ul><ul><li>The cell devotes a lot of ENERGY to pumping things across membrane </li></ul><ul><li>Potassium, calcium, and sodium are some things that need to pumped across </li></ul>
  17. 20. Endocytosis <ul><li>When cells need to take in large material </li></ul><ul><li>Process of taking material into the cell by process of infolding, or pockets, of the cell membrane </li></ul><ul><li>Pocket breaks loose from cell membrane and forms a vacuole inside the cell </li></ul><ul><li>Two Types… </li></ul><ul><ul><li>Phagocytosis </li></ul></ul><ul><ul><li>Pinocytosis </li></ul></ul>
  18. 22. Two types of endocytosis: <ul><li>1. Phagocytosis </li></ul><ul><ul><li>“ cell eating” </li></ul></ul><ul><ul><li>Extensions of cytoplasm surround the particle and package it within a food vacuole </li></ul></ul><ul><ul><li>Cell then engulfs the package </li></ul></ul><ul><ul><li>Amoebas </li></ul></ul><ul><li>2. Pinocytosis </li></ul><ul><ul><li>“ cell drinking” </li></ul></ul><ul><ul><li>When cell needs to take up liquid </li></ul></ul><ul><ul><li>Tiny pockets in cell membrane form </li></ul></ul><ul><ul><li>Fill with liquid </li></ul></ul><ul><ul><li>Then pinch off to form vacuoles inside of cell </li></ul></ul>
  19. 25. Exocytosis <ul><li>Exo- means… </li></ul><ul><li>Cyto means… </li></ul><ul><li>Sis means… </li></ul><ul><li>When cell releases large amounts of material </li></ul><ul><li>Excretes stuff </li></ul><ul><li>Membrane of vacuole surrounding particle inside cell fuses with the cell membrane </li></ul><ul><li>The contents in vacuole are then forced out of the cell </li></ul><ul><li>We see this in removal of water by contractile vacuoles </li></ul>