At the end of this unit you should

At the end of this unit you should be able to explain why the following occurs… § http: //www. youtube. com/watch? v=H 6 N 1 Ii JTmnc

Questions of the day… What keeps cells from exploding? Why do they “mist” or spray water at the grocery store? How does your body get the nutrients it needs in and the waste nutrients out of each cell?

Which cells have Cell Membranes?

Cell Membranes vs. Cell Walls § Cell Membranes regulate what comes into and out of cells § Cell Walls provide protection and support for the cell

Electron micrograph of cell membrane

Phospholipids make up cell membranes Polar “head” that is attracted to water Non-polar “tails” that are not attracted to water but are attracted to other phospholipid tails

Phospholipids make up cell membranes

Water molecules Polar head faces out towards water because of the attraction Nonpolar tails face inward so they are protected from water Water

Membranes are picky!!! § Membranes are semi-permeable because they only let certain molecules through § Small and non-polar molecules can pass through easily § Large and polar molecules cannot pass through without help § http: //www. youtube. com/watch? v=6 Rd 2 b Ep 380 w

Both water and nutrients can move in and out of cells.

Diffusion discusses the movement of particles Diffusion- The movement of particles from a region of higher concentration to a region of lower concentration, caused by the random motion of particles. Ex: Body Spray Food Coloring/Water

§ Osmosis- The diffusion of water across a semi-permeable membrane towards the side with higher solute concentration.

Draw a picture where molecules would diffuse out of a membrane

Draw a picture where molecules would diffuse into a membrane

Osmosis discusses water movement: § If there is more water outside(less particles)… § Water will move into the cell § If there is more water inside (more particles) § Water will move out of the cell

Draw a picture where water would move into the cell

Draw a picture where water would move out of a cell

Visual Examples Water will move into cell Water will move out of cell. Water will stay put.

Where will particles diffuse?

Lets set up a Lab § Purpose: To determine if glucose and starch are permeable through a model cell membrane. § Hypothesis:

Glucose § bonds have some areas of charge (somewhat polar) § http: //www. 3 dchem. com/molecules. asp? ID=423#

Starch Few areas of Charged bonds § Picture

How could we check for the presence of starch? § Starch turns black in the presence of Iodine

How could we check for the presence of sugar? § Glucose test strips tell presence of sugar

How could we set up an experiment to see if starch and sugar will move through a membrane?

Procedure: MATERIALS § § § 3 -150 m. L beaker 1 -10 m. L graduated cylinder 10% IKI solution 2 Glucose Test Strips 2 pieces of string (10 -20 cm)

Materials Continued § § 1 -20 cm piece of dialysis tubing 1 -100 m. L graduated cylinder 1 -Scissors Starch/Glucose Solution

§ 1. Record color of Initial Solutions § 2. Record Glucose presence of Starch/Glucose Solution (Done by Miss H) § 3. Obtain one piece of Moist Dialysis tubing § 4. Seal one end of the tube by folding the end over and tying with thread to form an open bag

§ 5. Obtain 10 m. L of Starch/Glucose Solution in your graduated cylinder § Fill your bag with Starch/Glucose solution (about 10 m. L) § Leave about 2 cm of room at the top of bag. § Squeeze excess air of of bag § Place your bag in the 150 m. L beaker and completely cover with 10% Iodine Solution

Procedure Continued. . § Tie up bag as shown by Miss H § Wait 10 minutes and remove your cell from the iodine. § Use scissors to empty contents of your cell into a clean beaker § Observe color and contents of the cell § Test contents for glucose § Test the iodine solution for glucose

What Data should we take?

Observations inside and outside of cell membrane Initial Cell Contents Color Glucose Test Strip Initial Beaker Final Cell Contents Final Beaker