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DNA

DNA. Compare and contrast prokaryotes and eukaryotes with your groupmates Put away everything but a pen or pencil. When Finished with Quiz…. Grab a computer for you and the person sitting next to you Log in – if it says you can’t shut off the computer, turn it on and try again

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DNA

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  1. DNA • Compare and contrast prokaryotes and eukaryotes with your groupmates • Put away everything but a pen or pencil

  2. When Finished with Quiz… • Grab a computer for you and the person sitting next to you • Log in – if it says you can’t shut off the computer, turn it on and try again • Google “PHET simulations” and play around with one of the simulations until everyone is done

  3. Crossing the Membrane

  4. Osmosis/Diffusion Activity • Work as partners – we’ll begin as a class

  5. Activity 1 • Start in one corner • Try to move randomly- when you (Carefully) bump into somebody “bounce” the other direction • What happens?

  6. Diffusion • We call this phenomenon diffusion • Things naturally bounce off each other and spread apart – if they can • We say things move from “high concentration” to “low concentration”

  7. What does this have to do with cells? • Lots of things enter and exit this cell by this process • However, they must be able to somehow cross the membrane Cytosol

  8. General Membrane Structure • Phospholipids with proteins embedded in the membrane • Different membranes have different proteins

  9. PhospholipidBilayer

  10. Observation 1 • Watch the water and oil, do they mix? • What happens when we drop food coloring into the oil layer?

  11. Hydrophilic and Hydrophobic Don’t Mix • The inside of the membrane is hydrophobic (oily) • Which means polar things will not mix well with it • Ions will definitely not mix well

  12. Membranes Keeps Cells Separate • Most things are either too big to cross the membrane • OR they are polar and won’t mix with the membrane • Creates an internal environment different from the outside world(i.e. it has enzymes, proteins, sugars, ATP, NADH, FADH etc. floating around)

  13. Simple Diffusion • Very small hydrophobic (non-polar) molecules can simply slip between the membranes and cross the hydrophobic layer • Water is small enough that some of it can slip through

  14. Facilitated Diffusion • Other small molecules need to move through a protein channel (small, polar or ionic compounds)

  15. Observe the Facilitated Diffusion • What will happen when we put a channel in the membrane?

  16. Concentration Gradient High Concentration Low Concentration

  17. Equilibrium / No Concentration Gradient • No net change in concentration. Molecules still move but on average the concentrations stay the same Medium Concentration Medium Concentration

  18. Facilitated Diffusion – 2 molecules

  19. What if We Want to Move Things Against the Gradient? • Active Transport! • We must invest energy to “pump” molecules

  20. Review • Small, non-charged molecules can simply diffuse • Small, polar or charged molecules can pass through a protein • Energy must be invested to move things against the gradient

  21. Endo/Exocytosis • Big things must enter through endocytosis and form a vesicle • Big things must exit by exocytosis, where the vesicle becomes part of the plasma membrane

  22. Selective Permeability • Membranes control what gets in and what gets out of the cell • Protein channels or pumps can be opened and closed

  23. Osmosis • Special name for diffusion of water • When molecules can’t diffuse, water does • Water diffuses towards the more concentrated side until the concentrations are balanced* • *or another force is applied

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