Warm Up 10/27 (Hint: Cells & Their Environment Guided Reading, pg 21 of notebook) 1)Define homeostasis 2) Draw a phospholipid. Label the nonpolar and polar portions of the phospholipid. 3) Label the different type of proteins in the cell membrane in the picture.

Cell Transport Substances can enter and leave the cell in many ways Sometimes, energy is needed, and other times, it is not…

Diffusion Diffusion occurs when substances move from an area of high concentration to an area of low concentration (when a concentration gradient exists) This does not require energy

Passive Transport Occurs when substances cross the cell membrane down their concentration gradient (they “diffuse” across the membrane) This does NOT require energy

Passive Transport Simple diffusion allows small nonpolar molecules to pass directly through lipid bilayer (ex: oxygen) Facilitated diffusion occurs when transport proteins help substances that can’t pass directly through lipid bilayer (ions and polar molecules) cross the membrane. –Even though transport proteins are involved, energy is NOT required!

Passive Transport Simple Diffusion Facilitated Diffusion

Osmosis Osmosis is the diffusion of water molecules across a cell membrane Osmosis allows cells to maintain water balance as their environment changes Since water molecules are polar, they must diffuse through special transport proteins (a form of facilitated diffusion)

Predicting Water Movement If in biology, there is a constant need to achieve equilibrium, where will the water move? 80% water 20% sugar 20% water 80% sugar Water will move into the cell The cell will expand This solution is HYPOTONIC

Predicting Water Movement If in biology, there is a constant need to achieve equilibrium, where will the water move? 20% water 80% sugar 80% water 20% sugar Water will move out of the cell The cell will shrink This solution is HYPERTONIC

Predicting Water Movement If in biology, there is a constant need to achieve equilibrium, where will the water move? 50% water 50% sugar 50% water 50% sugar Water will move into and out of the cell evenly The cell will remain the same This solution is ISOTONIC

Predicting Water Movement A solution is HYPERTONIC when it has a higher concentration of solutes and lower concentration of water than the cell – water will move out of the cell A solution is HYPOTONIC when it has a lower concentration of solutes and higher concentration of water then the cell – water will move into the cell A solution is ISOTONIC when it has an equal concentration of solutes and solvents than the cell – water will move into and out of the cell evenly with no net gain or loss

Predicting Water Movement The solutions in which these red blood cells are in are… HypertonicHypotonicIsotonic