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Cell Membranes

Explore the role of cell membranes in separating living from nonliving, understand the functions, structure, and transport mechanisms involved. Learn about passive processes like diffusion, osmosis, and active transport such as endocytosis and exocytosis.

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Cell Membranes

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  1. Cell Membranes Separating Dead from Alive

  2. Identify the radical below. • Amine • Hydroxyl • Carboxyl • Monosaccharide

  3. Identify the molecule shown. • Butene • Propene • Propane • Butane • None of the above are a good response.

  4. What is the function of the molecule shown below? • Energy storage • Component of cell membrane • Fuel source • Regulatory

  5. I. Functions Living part of the cell-legitimate cell organelle Separates living from the nonliving world Semipermeable-regulates what enters and exits the cell Partitions the cell into different regions where different functions take place Participates in chemical reactions Transmits signals between outside of cell and the cytoplasm[

  6. II. Cell membrane characteristics • A. Semipermeable • B. Elastic • C. Wettable • D. Very thin-around 10 um

  7. II. Early model • A. Davison Danielli Model 1. mainly lipid 2. aqueous channels 3. surface protein 4. weaknesses

  8. Phospholipids interacting in water-amphipathic

  9. RBC cell membrane-clearly resembles Davson-Danielli model

  10. III. Fluid mosaic model • A. Main ingredients • Phospholipids • Proteins both intrinsic and extrinsic • Cholesterol • Glycocalyx

  11. Your textbook’s Diagram

  12. B. Protein functions

  13. What do you think the function of this membrane protein might be? • Transport • Cell to cell adhesion • Cell to cell recognition • Energy production

  14. Electron micrograph of cell membrane • http://www.med.uiuc.edu/histo/large/atlas/image/temgi3/75000a1.htm

  15. C. Chemical properties of membrane • 1. Lateral fluidity • 2. Two dimensional fluidity-rapid movement of lipids and proteins • 3. Flexible • 4. Self sealing • 5. Can fuse

  16. C. Chemical properties of membrane • Effect of saturated vs. unsaturated • Role of cholesterol

  17. IV. Function of Cell Membrane-Passive Transport A. Diffusion 1. definition 2. example 3. across cell membrane

  18. Your textbook’s figure of diffusion

  19. IV. Function of Cell Membrane-Passive Transport • B. Facilitated Diffusion 1. mediated by intrinsic protein 2. diffusion gradient-no ATP 3. glucose entrance into cell 4. boy scout analogy

  20. C. Osmosis • 1. Definition • 2. U-tube • 3. Explanation • 4. Common examples • 5. Terms of tonicity • 6. Turgor pressure

  21. In which direction will water move? • A => B and B rises • B => A and A rises • A  B and the sides stay at the same level • No idea

  22. Your textbook’s figure of osmosis

  23. (b) (c) (a) Plasma membrane Nucleus Vacuole Vacuole Vacuolar membrane (tonoplast) Figure 5-13Page 106 Plasma membrane Cytoplasm

  24. V. Function of cell membrane-active transport • A. Definition • B. Endocytosis • 1. Phagocytosis

  25. Phagocytic vesicles

  26. 2. Pinocytosis Pinocytotic vesicle Microvilli Cytosol Figure 5-19Page 111

  27. 3. Receptor mediated pinocytosis 0.25µm (b) Figure 5-20bPage 112

  28. C. Exocytosis

  29. D. Membrane Pumps • Materials are moved against concentration gradient • An integral protein molecule is involved • ATP is necessary • Sometimes membrane potentials are produced • Na ion-K ion pump is an example

  30. ATP ADP 3. The transport protein under- goes a conformational change, releasing three sodium ions outside the cell. 2. A phosphate group is transferred from ATP to the transport protein 1. Three sodium ions bind to the transport protein 4. Two potassium ions bind to the transport protein 6. The transport protein returns to its original shape: Two potassium ions are released inside the cell 5. The phosphate is released Figure 5-15bPage 108 (b)

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