The Cell Membrane AP Biology

Transcription

1 The Cell Membrane

2 Warm Up What would happen if you gave a patient an IV of pure water? a. Their blood cells would shrink. b. Their blood cells would burst. c. The patient would slowly become rehydrated. d. I would be promoted for my outstanding level of medical care.

3 What you need to know You need to predict how molecules move across membranes You need to know the difference between active and passive transport

4 Overview Cell membrane separates living cell from surroundings Controls traffic in & out of the cell selectively permeable hydrophobic vs hydrophilic Made of phospholipids, proteins & other macromolecules

5 Phospholipids Fatty acid tails hydrophobic Phosphate group head hydrophilic Arranged as a bilayer Phosphate Fatty acid Aaaah, one of those structure function examples

6 Movement across the Cell Membrane

7 Diffusion Diffusion movement from high low concentration

8 Diffusion Move from HIGH to LOW concentration passive transport no energy needed movement of water diffusion osmosis

9 Diffusion through phospholipid bilayer What molecules can get through directly? fats & other lipids inside cell NH 3 lipid salt What molecules can NOT get through directly? polar molecules H 2 O ions outside cell sugar aa H 2 O salts, ammonia large molecules starches, proteins

10 Channels through cell membrane Membrane becomes semi-permeable with protein channels specific channels = specific materials inside cell H 2 O aa sugar NH 3 salt outside cell

11 Facilitated Diffusion Diffusion through protein channels channels move specific molecules across cell membrane no energy needed open channel = fast transport low facilitated = with help high The Bouncer

12 Active Transport Cells may need to move molecules from low to high concentration protein pump used costs energy (ATP) low conformational change ATP high The Doorman

13 Active transport Many models & mechanisms ATP ATP antiport symport

14 Getting through cell membrane Passive Transport Simple diffusion diffusion of nonpolar, hydrophobic molecules lipids high low concentration gradient Facilitated transport through a protein channel high low concentration gradient Active transport diffusion against concentration gradient low high uses a protein pump requires ATP ATP

15 Transport summary simple diffusion facilitated diffusion active transport ATP

16 How about large molecules? Moving large molecules into & out of cell through vesicles & vacuoles endocytosis phagocytosis = cellular eating pinocytosis = cellular drinking exocytosis exocytosis

17 The Special Case of Water Movement of water across the cell membrane

18 Osmosis is diffusion of water Diffusion of water from high concentration of water to low concentration of water Across membrane

19 Concentration of water Direction of osmosis is determined by comparing total solute concentrations Hypertonic - more solute, less water Hypotonic - less solute, more water Isotonic - equal solute, equal water water hypotonic hypertonic net movement of water

20 Managing water balance Cell survival depends on balancing water uptake & loss freshwater balanced saltwater

21 Water regulation Contractile vacuole in Paramecium ATP

22 Osmosis.05 M.03 M Cell (compared to beaker) hypertonic or hypotonic Beaker (compared to cell) hypertonic or hypotonic Which way does the water flow? in or out of cell

23 Exit Ticket: Justify Why! An animal cell is placed in a saltwater solution. Predict what might happen to the cell when exposed to this solution. Describe the solution too. Is it hypertonic, hypotonic, or isotonic?

24 Any Questions??