Bell work 1.Please pick up the study guide from the side table. 2.You will have a test on cell membrane structure and function on Monday. 3.Complete side 1 of the study guide. 4.Study guide will not be collected until day of the test.

The importance of homeostasis Cells depend on the body environment to live and function. Homeostasis keeps the body environment under control and keeps the conditions right for cells to live and function. Without the right body conditions, certain processes (eg osmosis) and proteins (eg enzymes) will not function properly.

Why is homeostasis important for cells? Living cells depend on the movement of chemicals around the body. Chemicals such as oxygen, carbon dioxide and dissolved food need to be transported into and out of cells. This is done by the processes of diffusion and osmosis, and these processes depend on the body's water and salt balance, which are maintained by homeostasis. Cells depend on enzymes to speed up the many chemical reactions that keep the cell alive and make it do its job. These enzymes work best at particular temperatures, and so again homeostasis is vital to cells as it maintains a constant body temperature.

Homeostasis and Diffusion Homeostasis maintains the correct body conditions in order for diffusion to take place. Remember: Particles continue to move from a high to a low concentration until all the particles are evenly and randomly distributed.

Osmosis Osmosis is simply a special type of diffusion. It occurs when water molecules pass through a partially permeable membrane. Some membranes in plant and animal cells allow certain particles to pass through them but not others. They are partially permeable membranes.

Which side has a higher concentration of water?

Predict: What will happen to the water levels on each side of the membrane?

Osmosis and homeostasis Osmosis is the overall movement of water from a dilute solution to a more concentrated solution through a partially permeable membrane. This is still like diffusion, as the water is moving from a higher concentration of water to a lower concentration of water. When the concentration of water is the same on both sides of the membrane, the movement of water will be the same in both directions. At this point, the net exchange of water is zero, and the system is in equilibrium.

Direction of water flow depends on tonicity of solutions inside and outside of the membrane. CELL IN HYPOTONIC SOLUTION (low/below) CELL IN ISOTONIC SOLUTION (same/normal) CELL IN HYPERTONIC SOLUTION (high/above)

Compare the internal environment to the external environment.

Which direction will water move? Cell___________________ Surroundings___________ Cell___________________ Surroundings___________ Cell___________________ Surroundings____________

What is causing the change in shape of the red blood cell? Red blood cell in Isotonic solution

When does a cell undergo cytolysis?

Why don’t plant cells undergo cytolysis?

When do plant cells undergo plasmolysis?