Cells and Their Environment Chapter 4 p 74-84

Homeostasis A biological balance Cells, tissues, organs, and organisms must maintain a balance. Cells do so by controlling and regulating what gets into and out of the cell.

Transport Passive Active Transport that does not require chemical energy to occur ie: diffusion and osmosis Active The movement of any substance across a cell membrane with the use of chemical energy ie: Na+/K+ pump

DIFFUSION Process by which molecules spread from an area of high concentration to an area of low concentration Concentration gradient: a difference in the concentration of a substance Examples: Oxygen diffusing into cells Beaker of water with food coloring Smell of perfume in a room ***Molecules are in constant motion

Diffusion animations http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.html http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

Osmosis Diffusion of water through a membrane from an area of high concentration to an area of low concentration. What determines the direction in which water molecules diffusion across a cell membrane? **the concentration of water and of solutes dissolved in the solution

http://www. stolaf. edu/people/giannini/flashanimat/transport/osmosis http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html http://www.wiley.com/legacy/college/boyer/0470003790/animations/membrane_transport/membrane_transport.htm

Think about it… What happened if you eat salty foods? Grass wilts if you add too much fertilizer…WHY?

Cells can be found in 1 of 3 solutions: HypOtonic 2. Hypertonic 3. Isotonic

HYPOTONIC Concentration of solute molecules in the environment outside of the cell is lower than that in the cell. Water moves in

Red blood cell

Hypertonic Concentration of solute molecules outside the cell is greater than that in the cell Water moves out

Isotonic Concentration of solute molecules outside cell and inside are equal. **equilibrium

Facilitated diffusion Use of carrier to “help” move molecules across a membrane Passive: energy Y or N? Gradient: H to L Example: glucose

Filtration Type of Transport: Passive Using pressure to push something through the cell membrane Energy needed?? Example…what organ in your body filters

Active transport Movement of substances through a membrane from a low to high concentration with the use of energy. ATP: energy form Usually Low to high concentration “Against a gradient” Example: Na/K pump.

Active Transport http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html

Some molecules are too large to pass thru membrane Some molecules are too large to pass thru membrane!!! Even with use of energy Endocytosis…movement of substances into the cell by transport vesicles into the cell. Exocytosis… movement of substances outside of the cell by transport vesicles into the cell

Endocytosis

Exocytosis

http://www.coolschool.ca/lor/BI12/unit4/U04L05.htm http://www.wiley.com/college/boyer/0470003790/animations/membrane_transport/membrane_transport.htm http://www.teachersdomain.org/asset/tdc02_int_membraneweb/