1. Homeostasis, Cell Membrane, & Transport Notes
Unit 2
Fall 2014

2. Bellringer 9/19/14
Correct your bellwork from Monday: “lower, increase”
Which organelle has digestive enzymes that breaks down waste and bacteria?
A. nuclear membrane
B. mitochondria
C. lysosome
D. ribosome
Which organelle is described as “little grains floating around inside the cell and on the rough ER where proteins are made”?
Ribosome
Nucleus
Mitochondria
Centriole

3. Bellringer 9/22/14
Correct your bellwork from Monday:
Q1. lysosome, Q2. ribosome
Put your project on the front table (where the bins are). MAKE SURE YOUR NAME IS ON THE LOWER RIGHT HAND SIDE!!
Complete the extra credit on your progress report if you have it.
In an animal cell, which of the following structures would be used for locomotion?
A. flagellum
B. plasma membrane
C. microtubules
D. secretory vesicle

4. Homeostasis Homeostasis = maintaining stable internal conditions
Keeping everything the same
Cells are always trying to maintain homeostasis!!

5. Examples of Homeostasis in your body
Blood sugar levels
Temperature
pH in blood
Water balance

6. Remember this? 

7. What maintains homeostasis in a cell?
The cell membrane
The cell membrane controls what enters and exits the cell!!
Acts like border patrol

8. Cell Membrane
Cell Membrane is selectively permeable: it allows some substances in and keeps others out

9. Cell Membrane
Referred to as the Phospholipid Bilayer: 2 layers of phospholipids with proteins and cholesterol scattered throughout

10. Cell Membrane: Phospholipid
Phosphate heads
Close to the water in the cytoplasm and outside of the cell
Face outward because they are HYDROPHILIC
Fatty acid tails
Face inward because they are afraid of water (HYDROPHOBIC)!!
Creates a barrier between the inside and outside of the cell

11. Fluid Mosaic Model
The cell membrane is often referred to as a “fluid-mosaic model”
Mosaic because of the proteins and cholesterol embedded in the phospholipid bilayer
Fluid because cell membranes have the consistency of vegetable oil at body temperature, so substances can move across it!!
Fluid Mosaic Model:

12. Proteins in the Membrane
Span the phospholipid bilayer
May be passive or active
Two types: carrier & channel

13. Types of Cell Transport
Passive Transport: requires no energy (ATP) Active Transport: requires energy (ATP)

14. Passive Transport
Three types:
Diffusion
Osmosis
Facilitated Diffusion

15. Diffusion
Molecules automatically move from areas of high concentration to low concentration
Why? Because molecules are constantly moving & colliding
Diffusion continues until it is equal everywhere in space = equilibrium

16. Diffusion Examples Teabag placed in hot water
Strong perfume or cologne sprayed in a room (think middle school locker room)
Oxygen diffuses from blood cells in the blood stream into muscles

17. Concentration Gradients
Molecules always move down their concentration gradient
Moving from high concentration to low

18. Osmosis The diffusion of water is called osmosis
Osmosis = water moving from high concentration to low concentration

19. Osmosis
When two fluids on opposite sides of a membrane have different solute concentrations, water will always move from high concentration to low concentration

21. Solutes & Solvents
Solute = substance that is dissolved in a solvent to make a solution
Solvent = substance in which a solute is dissolved

22. Making Koolaid Solutes = Koolaid powder & sugar Solvent = water
Koolaid drink = solution

23. Hypotonic Solution
The concentration of solutes outside of the cell is less than the concentration inside of the cell
There is more water outside of the cell than inside of the cell
More water will enter the cell than leave the cell so the cell will swell and can possibly burst

24. Hypertonic Solution
The concentration of solutes outside of the cell is greater than the concentration inside of the cell
There is more water inside of the cell than outside of the cell
More water will leave the cell than enter the cell so the cell will shrink or shrivel.

25. Isotonic Solution
The concentration of solutes outside of the cell is equal to the concentration inside of the cell
There is the same amount of water inside of the cell as outside of the cell
Equal amounts of water will enter and leave the cell so the size of the cell will not change

26. Animal Cells
Shrivel Stay the same Lyse

27. Plant Cells What keeps plant cells from lysing (bursting)?
Cell Walls!!

28. Osmosis Practice

29. More Osmosis Practice
: Egg Osmosis

30. Diffusion is great, but…
What if a cell needs to move large or polar molecules that can’t get through the membrane?
What if a cell needs to move a molecule AGAINST the concentration gradient? (lower concentration to higher concentration)

31. Diffusion is great, but…
Cells need a way to help molecules across a membrane that can’t go across by themselves
Two options:
Facilitated Diffusion
Active Transport

32. Facilitated Diffusion
Type of diffusion that uses membrane proteins to help molecules across if they are too large or polar
Does not take any energy  powered by the concentration gradient
Still a PASSIVE form of transport!

33. Facilitated Diffusion

34. Facilitated Diffusion
Carrier Proteins work by grabbing the molecule, changing shape, and flipping it across the other side like a revolving door

35. Facilitated Diffusion
Channel Proteins work by creating a tunnel through which molecules can pass

36. Active Transport
When a cell wants to move against it’s concentration gradient (from low concentration to high concentration) it needs energy.
Requires ATP!
Three types of Active Transport:
Protein Pumps
Endocytosis
Exocytosis

37. Sodium Potassium Pump Special just for Na+ and K+ ions
Uses membrane proteins called protein pumps to move molecules
Moves Na+ and K+ against their concentration gradients in order for your nerve cells to work properly

38. Na+ and K + PUMP See a movie about Na+ - K+ pump
Animation from:
See a movie about Na+ - K+ pump

39. Proton Pump Moves protons (H+) across membranes using a protein pump
Special just for H+ ions
Can change the pH levels needed for certain reactions
Example: lysosomes need acidic conditions in order to break down cellular waste

41. Endocytosis Active transport (requires ATP!)
Uses vesicles to carry substances INTO the cell
Can move molecules from low concentration to high
Examples in cells:
Unicellular organisms eat this way
White blood cells get rid of bacteria this way

42. Exocytosis Active transport (requires ATP!)
Uses vesicles to release substances OUT of the cell
Can move molecules from low concentrations to high concentrations
Examples in cells:
Golgi bodies release packaged proteins this way

43. Review!!