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The Cell Membrane

The Cell Membrane. Cell Membrane. All membranes of a cell have a similar basic structure: proteins floating in a double layer of lipids. Lipids are responsible for the isolating functions of a membrane Proteins control the exchange of substances and communication with the external environment.

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The Cell Membrane

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  1. The Cell Membrane

  2. Cell Membrane • All membranes of a cell have a similar basic structure: proteins floating in a double layer of lipids. • Lipids are responsible for the isolating functions of a membrane • Proteins control the exchange of substances and communication with the external environment

  3. Cell Membrane • The cell membrane is also known as a phospholipid bilayer: • (Bi means two) • Each layer is made up of: • Phosphate heads- polar, hydrophilic • Hydrophilic= water loving • Fatty acid tails- nonpolar, hydrophobic • Hydrophobic= water scared

  4. A closer look at the lipid bilayer…

  5. A closer look at the protein structure inside the membrane…

  6. Cellular Transport

  7. Components of a Solution 1. Solute - the part of the solution that is being dissolved (ex: kool-aid powder)

  8. Components of a Solution 2. Solvent - the part of the solution that is doing the dissolving (ex: water)

  9. Types of Cellular Transport Passive Active

  10. Passive Transport *Definition: movement with the concentration gradient (moves from an area of HIGH concentration to an area of LOW concentration) • does not require energy Simple Diffusion Animation

  11. What’s happening?

  12. Examples of Passive Transport • Diffusion the movement of solutefrom an area of HIGH concentration to an area of LOW concentration

  13. The diffusion of solutes across membranes

  14. Examples of Passive Transport • Facilitated Diffusion: the movement of solutes through the protein channels of the cell membrane from an area of HIGH concentration to an area of LOW concentration

  15. Two models for facilitated diffusion Facilitated Diffusion Animations

  16. Examples of Passive Transport • Osmosis the movement of WATER (the solvent) through the cell membrane from an area of HIGH concentration to an area of LOW concentration

  17. Importance of Cellular Transport: Helps the cells (and the body) maintainhomeostasis (if there is too much of something in a cell, transport it out; if there is not enough of something in a cell, transport it in)

  18. Hypertonic, Hypotonic, and Isotonic Solutions

  19. How does Passive Transport affectmy cells?

  20. 80% H2O 80% H2O 80% H2O 70% Water30% Dissolved Substances 100% Distilled Water 80% Water20% Dissolved Substances Predict… What would happen to the animal cells in each beaker?

  21. 80% H2O 100% Distilled Water Which way did the water move? Why did the cell get so big?

  22. 80% H2O 80% Water20% Dissolved Substances Which way did the water move? Why did the cell stay the same size?

  23. 80% H2O 70% Water30% Dissolved Substances Which way did the water move? Why did the cell get so small?

  24. Importance of Cellular Transport: Helps the cells (and the body) maintainhomeostasis. Homeostasis – when a system can regulate its environment to remain stable

  25. There are 3 possibilities for the direction of water movement 1. Water can move out of the cell. 2. Water can move into the cell. 3. There can be no net movement of water. There are special names for these…

  26. Hypertonic If the environment… has a higher solute concentration than the cell. Then outside fluid is… hypertonic. Water diffuses… out of the cell. Effect on the cell… Loses water (loses mass) and shrivels up H₂O

  27. Hypotonic If the environment… has a lower solute concentration than the cell. Then outside fluid is… hypotonic. Water diffuses… into the cell. Effect on the cell… Gains water (gains mass) and expands H₂O

  28. Isotonic If the environment… and the cell have equal concentrations of solutes. Then outside fluid is… isotonic. Water diffuses… into and out of the cell at equal rates (no net movement). Effect on the cell… mass stays the same and so does the cell

  29. The water balance of living cells

  30. Active Transport * movement of solute against the concentration gradient (low concentration to high concentration) * requires energy

  31. What is this cell doing?

  32. Endocytosis • Cells bring large in particles using cell membrane • There are 2 types: • Phagocytosis • Pinocytosis • Channel proteins are used to bring in large molecules.

  33. Phagocytosis • Your white bloods cells also do this. • This is the ingestion of large particles. Amoeba

  34. Pinocytosis • Tiny pockets form along cell membrane, and pinch off into vacuoles inside the cell. Sometimes called “Cell Drinking”

  35. Exocytosis • This is how the cell gets rid of waste.

  36. The three types of endocytosis in animal cells

  37. Review: passive and active transport compared

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