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Chapter 5 Homeostasis and Transport

Chapter 5 Homeostasis and Transport. Homeostasis & Transport. BIG IDEAS: Cell Membranes help organisms maintain homeostasis by controlling what substances enter and leave the cell. Some substances can cross the cell membrane without any energy input from the cell.

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Chapter 5 Homeostasis and Transport

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  1. Chapter 5 • Homeostasis and Transport

  2. Homeostasis & Transport • BIG IDEAS: • Cell Membranes help organisms maintain homeostasis by controlling what substances enter and leave the cell. • Some substances can cross the cell membrane without any energy input from the cell. • Some substances require a cell to expend energy to enter or leave the cell.

  3. How Materials Enter and Leave Cells For cells to remain alive, a certain combination of chemicals must be able to be present inside its cell membrane. The cell membrane is one of the structures that helps maintain this special environment inside and outside the cell. • How does the cell move materials into and out of a cell? • One way molecules of a substance get into and out of a cell is by a process known as passive transport • Passive transport is the diffusion or movement of molecules across a cell membrane. It does NOT REQUIRE any ENERGY input from the cell.

  4. The Cell Membrane The cell membrane is Selectively Permeable. Meaning, it allows the passage of some substances and blocks other or not required substances.

  5. The Cell Membrane • This selectively permeable membrane only allows certain things in/out of the cell. • Made of protein and lipids • BILAYER-two layers; the head of the molecules face outward while the tails face inwards. • PHOSPHOLIPID-molecule that makes up the cell membrane. Has two parts. • 1. The phosphate head (hydrophilic – water loving) • 2. Two lipid tails (hydrophobic – water hating)

  6. Passive transport Molecules diffuse or move from an area of higher concentration to an area of lower concentration. THEY MOVE DOWN A CONCENTRATION GRADIENT! • Substances crossing the cell membrane without any input of energy by the cell – move down their concentration gradient • Types: • Simple Diffusion • Osmosis • Facilitated Diffusion • Ion Channels • http://www.youtube.com/watch?v=JShwXBWGMyY

  7. ?? Concentration Gradient DOWNA CONCENTRATION GRADIENT. • = a gradient results from an unequal distribution of dissolved molecules across the cell membrane. When this happens, solutes downconcentrationgradient. • This kind of movement is called diffusion.

  8. Diffusion • Diffusion Stops when…Molecules reach EQUILIBRIUM • The concentration of the molecules is the same throughout a space. • No more diffusion! But molecules keep moving. • EXAMPLE: food coloring, cookie smell in your house, etc. • The simplest type of passive transport is diffusion. Diffusion is the natural movement of molecules from an area of high concentration to an area of low concentration. • Molecules naturally intermingle as a result of their kinetic energy of random motion.

  9. Diffusion

  10. Diffusion

  11. Diffusion Across a Cell Membrane REMENBER - The cell membrane is Selectively Permeable. There are tiny pores or holes in it that allow some molecules to diffuse into the cell. For example, oxygen molecules diffuse into your blood stream through the membranes of cells in your lungs. http://videos.howstuffworks.com/hsw/23424-cell-diffusion-across-the-cell-membrane-video.htm

  12. Osmosis Osmosis takes place through passive transport. • A cell is made up mostly of water and dissolved substances. Water can move into or out of a cell through the cell membrane. • The diffusion of water through a cell membrane is called osmosis.

  13. Osmosis • Osmosis maintains the balance of water inside and outside the cell. • Question?? • If there is more salt outside of the cell, will water move into the cell or out of the cell?? • The direction that water moves depends on the amount of dissolved substances inside and outside of a cell. • If there are more dissolved substances inside the cell, water will move into the cell and vise-versa. • Water will move to where there is LESS WATER.

  14. Water goes where it aint !!

  15. Example of Osmosis http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf

  16. The net movement of water, or osmosis, depends on the type of environment the cell is in. Three types of environments: Isotonic Hypertonic Hypotonic 3 Types of Environments

  17. Isotonic: • Concentration of water is equal inside and outside of the cell. • Water will diffuse into and out of the cell at an equal rate • No net movement of water. • Cell stays the same.

  18. 2. Hypertonic • More water inside the cell, less outside. • More solutes outside the cell than INSIDE the cell. • Water moves out of the cell until equilibrium is reached. • Net movement of water is out of the cell. • Can cause the cell to shrink or shrivel. • Crenation in animal cells • Plasmolysis in plant cells

  19. 3. Hypotonic • More water outside the cell, less inside the cell. • More solutes inside, less solutes OUTSIDE the cell. • Net movement of water into the cell. • Can cause cell to burst. • CYTOLYSIS-cells take in so much water that they burst.

  20. The Effects of Osmosis on Animal Cells osmosis

  21. Osmosis in Plants Remember Plant cells store water in vacuoles. http://www.kscience.co.uk/animations/turgor.htm FYI - Plants whose cells do not have enough water appear dry and may droop. However, once the plant receives water, its cells may absorb the water through osmosis. Once water is absorbed into its cells, the plant swells. It will probably stand up straight and appear healthy. This is referred to as “Turgor” and is determined by osmosis.

  22. Plant cell membranes can be seen pulling away from their cell wall, in a process called plasmolysis, as their cells lose water. DRAWOsmosis in Plant Cells • Plant Cell • Cell Wall Vacuole Cytoplasm Cell Membrane • The Cell absorbs water …But the cell wall stops • by osmosis… the cell from expanding

  23. DRAW Cells in 3 Types of Solution! crenation cytolysis plasmolysis

  24. SALT SUCKS!!! Wherever there is more solute (i.e. salt, sugar), that is where water will be pulled to  WATER WILL MOVE TO WHERE IT AINT!! Remember:

  25. Respond to the following in your journal: Why do supermarkets have sprinkler systems set up in their produce section? Explain. Do Now

  26. Facilitated Diffusion Like diffusion, molecules are still moving from an area of higher concentration to an area of lower concentration. • Facilitated Diffusion: • Facilitated diffusion is the form of passive transport in which carrier proteins embedded in the cell membrane help or facilitate the movement across it. • It does not require the cell to use any energy.

  27. Ion Channels Like diffusion, molecules are still moving from an area of higher concentration to an area of lower concentration. • Some ions are important for cell functions (Na+, K+, Ca2+ and Cl-) • Since they are charged and hydrophilic, they can’t get across the lipid bilayer. • Ion channels – specific membrane proteins that help ions get across c ell membrane – some are always open, some are gated and require a stimuli to open. • EXAMPLE: impulse from nerve travels to muscle cell-causes some gated channels to open. • It does not require the cell to use any energy.

  28. Active Transport Most plants get water and minerals they need from their roots. Minerals enter the root by active transport. Active transport is also needed to move certain waste materials out of a cell. • Active Transport: • Movement through the cell membrane that • is the opposite of diffusion. • Molecules of certain substances move through the cell membrane from an area that is less crowded to an area that is more crowded is called ACTIVE TRANSPORT. • Energy is needed to move these materials across the cell membrane - Molecules move AGAINST the concentration gradient!! • http://www.youtube.com/watch?v=STzOiRqzzL4&feature=related

  29. Types of Active Transport • Cell Membrane Pumps • Endocytosis • Exocytosis

  30. Cell Membrane Pumps • SODIUM (Na+)/Potassium (K+) Pump • Uses a special carrier molecule. • K+ (potassium) goes into the cell. • Na+ (sodium) leaves the cell • Uses energy from the cell • Carrier proteins also help out in active transport and work against the concentration gradient: • Low High • Similar to facilitated diffusion, but a cell’s energy is required.

  31. Passive vs. Active Transport Low Concentration High Concentration Passive Transport High Concentration Active Transport Low Concentration

  32. Endocytosis & Exocytosis Cells have two processes of moving large particles across the cell membrane: Endocytosis and Exocytosis Endocytosisis the process by which the cell Membrane wraps around the large particle, forms a vesicle, and pulls it inside the cell. Once inside, the vesicle releases the particle. • 2 Ways: • 1. Pinocytosis-movement of solute or fluid into the cell. • 2. Phagocytosis-movement of large food particles or entire microorganisms into the cell.

  33. Endocytosis & Exocytosis Exocytosisis exact opposite. When the cell wants to get rid of a large particle, it encloses the particle inside a vesicle. The vesicle fuses with the cell membrane and the cell can then release the particle. http://media.pearsoncmg.com/bc/bc_campbell_biology_7/media/interactivemedia/activities/load.html?7&G

  34. Endocytosis & Exocytosis

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