1. Homeostasis
*All living things must maintain a balance regardless of internal and external conditions

2. Homeostasis
The process of maintaining equilibrium in the cell’s internal environment, a resistance to change
*This is similar to a thermostat in your home

4. Important terms to know:
Solute: substance being dissolved in another substance (often the lesser quantity)
Solvent: substance that dissolves another substance
Example: Kool-Aid, Which is the solute and which the solvent?

5. Mixture vs. Compound
Compound: cannot be easily separated by physical methods
The chemical/physical properties are totally different than the properties of the parts

6. NaCl H2O2 Na-very reactive, whitish, Cl-poisonous, green gas
We know this compound as table salt.
H2O2
H2- explosive gas, O2-flammable gas
We know this compound as hydrogen peroxide.

7. Mixture: can be easily separated by physical methods
The chemical/physical properties remain the same

8. Three types of mixtures:
1. Solution: two or more substances in a single phase, does not settle out, it is mixed evenly 
*solute molecules are smaller than in the solvent
ex. Sugar water

9. Three types of mixtures:
2. Suspension: solute larger than solvent will settle out over time, unless the mixture is constantly stirred or agitated 
ex. muddy water-mud settles when not stirred, particles can be separated

10. Three types of mixtures:
3. Colloid: particles of solute and solvent are mainly the same size, gel-like
small particles remain suspended
ex. types of emulsion-oils, waxes
smoke, fog-liquid in gas

11. Each of these mixtures is in our body:
Solution: salt water
Suspension: blood
Colloid: Cytoplasm

12. Major part of cells that maintain homeostasis:
1. Plasma Membrane:
a. Function: boundary between cell and its environment, allows steady supply of nutrients to come into the cell and excess wastes out-too much can be harmful
Cells need nutrients-glucose, amino acids, lipids

13. b. Selective permeability: allows some molecules in and keeps others out
c. Structure:
phospholipid bilayer: two layers of phospholipids back to back
glycerol, fatty acids, phosphate
Nonpolar: phospholipids, no charge
Polar: phosphate can dissolve other substances
(“like dissolves like”…so nonpolar can only dissolve nonpolar)

14. Hydrophobic: water fearing Hydrophilic: water loving
Water is polar, so it can interact with phosphate (facing outside of the cell)
Fatty acids avoid water (face middle of cell membrane)
Hydrophobic: water fearing
Hydrophilic: water loving

15. d. Fluid mosaic model: membrane is flexible, proteins create a pattern on the membrane surface
Transport proteins: allow needed material or wastes to move through the membrane, movement of substances in a mixture

16. Processes used to maintain homeostasis:
1. Diffusion: net movement of particles from an area of higher concentration to an area of lower concentration until it reaches equilibrium
*results due to the random movement of particles, a slow process

18. 3 Key factors of diffusion
1. Concentration: more concentrated, more rapid diffusion
2. Temperature: increase in temp. speeds up the movement of molecules and then diffusion
3. Pressure: increase in pressure, accelerate molecule movement and diffusion

20. Goal of cell is to have:
Dynamic Equilibrium: continuous movement of molecules, same rate in and out of the cell, but no overall concentration change
Concentration gradient:
difference in concentration
across space

21. Processes used to maintain homeostasis continued…
2. Osmosis: diffusion of water across a semi-permeable membrane
water flows to side of cell with less water, where water concentration is low
*water continues to diffuse until it is in equal concentration on both sides of the membrane

23. 3 types of solutions, osmosis in cells
1. Isotonic solution: The concentration of solute inside and outside the cell are the same, so water moves in and out of the cell at the same rate
*shape and size of the cell are normal, do not experience osmosis, water concentration is the same in and out of the cell

24. 3 types of solutions, osmosis in cells
2. Hypotonic: solute concentration is low outside the cell, water concentration or amount is lower inside the cell so water moves into the cell
*shape and size of cell swells beyond normal pressure increases, can cause cytolysis
Result: animal cells can burst, plant cells become firm due to turgor pressure

25. 3 types of solutions, osmosis in cells
3. Hypertonic: solute concentration outside the cell is higher than in the cell, so water concentration or amount is less outside the cell, so water moves out of the cell
*size of cell decrease for animal cells, causes plasmolysis
Result: animal cell shrinks, vacuole in plant cell shrinks, plant wilts

27. Turgor pressure vs. plasmolysis vs. cytolysis
Turgor pressure: in hypotonic cells, when water moves into cell the pressure increases and makes cell rigid
Plasmolysis: water leaves cell and cell wilts
Cytolysis: cells take in too much water and burst, only in animal cells

28. Water regulation in organisms
Single celled: most found in hypotonic environments, lakes and ponds
*Want to avoid bursting, have contractile vacuoles that act as a pump and remove water by contracting

29. 2. Higher level animals: cells in a hypertonic environment: no water, high-salt
Small portion of cells in the brain shrink and cause thirst
Cells in hypotonic environment drink too much water, low salt
*Small patch of cells in brain when they swell trigger nerves in kidney and cause kidney tubules to open up and produce more urine

30. Passive transport: no energy is needed to move the particles across the membrane
Ex. Diffusion and osmosis

31. Moves sugars and amino acids
Facilitated diffusion: passive transport of materials with the help of proteins
Moves sugars and amino acids

32. Active transport: movement of particles through a membrane

33. End of homeostasis notes