 Phospholipid-bilayer  Around outside of cell’s cytoplasm  Semi permeable  Regulates what enters and leaves the cell.  Maintains Homeostasis  Protects and supports the cell.

 movement of molecules from high to low [ ] (concentration)  spreads out evenly until equilibrium is reached

No Movement

 movement of substances across the cell membrane without any input of energy (ATP) by the cell  HIGH [ ] to low [ ] PASSIVE TRANSPORT

Ion Channels & Facilitated Diffusion  move molecules across the cell membrane through carrier/transport proteins  are specific for the type of molecule they help diffuse

 substances can cross the cell membrane with an input of energy (ATP) from the cell  Low [ ] to HIGH [ ]

 the process by which cells ingest “stuff” using vesicles

Exocytosis  the process by which cells release “stuff” (reverse of endocytosis)

Materials: (per group of two students)  1 plastic bag  1 pair of scissors  15 cm of string  1 token per student The Problem: Get the token into the bag according to the following rules:  The token must enter through a solid part of the bag.  The inside of the bag may not be directly open to the external environment.  The token entering the bag must remain clustered together.  You may have your hands in the bag to act as the inside of a cell.

  Exocytosis by paramecium bHg  Endocytosis by amoeba  PL_JrQv0cdUS_Pn4zUe2THWfMS1YHxyxL8 PL_JrQv0cdUS_Pn4zUe2THWfMS1YHxyxL8

OSMOSIS and DIFFUSION

Osmosis = diffusion of water A solution may be one of the following:  hypotonic solution: lower [ ] of solute, a lot of water  isotonic solution: same [ ] of water and solute  hypertonic solution: higher [ ] of solute, less water

Hypotonic – The solution on one side of a membrane where the solute concentration is less than on the other side. Hypotonic Solutions contain a low concentration of solute relative to another solution. Hypertonic – The solution on one side of a membrane where the solute concentration is greater than on the other side. Hypertonic Solutions contain a high concentration of solute relative to another solution.

ELODEA CELLS As viewed under the microscope

- Plasmolysis = cells shrink when turgor pressure is lost - the reason plants wilt

 We will be putting one baby carrot in a small amount of distilled water and another in a small amount of saturated salt water (NaCl).  We will be recording their initial and final masses, and observing any textural changes.  Hypothesis: What do you think will happen to each of these carrots?

 Data:  Day 1:  Mass of each carrot  Weighing boat needs to be clean and dry  Texture/qualitative observations of each carrot

 Osmosis and Diffusion

1. Compare and contrast osmosis and diffusion. 2. Where is osmosis most likely to occur? Diffusion?

1. Do you think osmosis occurred? What is your evidence? 2. Draw a picture of how you think water moved into or out of the carrots in each solution (distilled water and salt water).

1. Obtain one cellulose bag and tie one end in a knot. 2. Put 10 mL of starch solution in the bag. 3. Tie other end of bag securely with a string. 4. Dry the bag. This is now your “cell.” 5. Place 10 drops of iodine in a beaker. 6. Add approximately 150 mL of tap water to the beaker. 7. Observe the color of the “cell” and record its appearance. 8. Place the “cell” in the 150 mL beaker. 9. Observe and record any differences after 15 minutes

1. Did diffusion occur? If so explain which molecules moved and why. 2. Was the dialysis tubing a selectively permeable membrane? If so, explain and provide evidence for how you came to this conclusion.

 Write a script for interviewing a cell including the following:  Series of creative, content-based questions  Interview a cell about maintaining homeostasis  Supply the cell’s answers to the questions