Happy Birthday Alexandra & Cameron!!!! Date: November 23, 2015 Aim #29: How can the process of diffusion and the structure of the cell membrane help the cell maintain homeostasis? HW: Cell Web Quest due Tuesday 12/1 QUIZ- Tuesday/Wednesday (Aim #’s 24-26) Unit 3 Test- Monday (12/7)/Tuesday (12/8) Do Now: Warm-Up Notebook Date Title of Activity Page # 11/23 Other Organelles 52

Aim #29: How can the process of diffusion and the structure of the cell membrane help the cell maintain homeostasis?

1) What is diffusion? The net movement of particles from where they are more concentrated to where they are less concentrated. 2) What do we mean when we say concentration? The amount of a particular substance

It’s all about concentration

3) The reason diffusion occurs is because molecules are always… MOVING

Why are particle always moving? ENERGY Particles are in constant motion because they have energy

4) What is the end result of diffusion? The number of particles are now evenly distributed This is called: Dynamic Equilibrium

Dynamic Equilibrium YES At this point, the number of particles have spread themselves out equally throughout the beaker. 5) Are the particles still moving after dynamic equilibrium has been reached? YES

An illustration of diffusion:

6) What are the two Conditions for diffusion to occur? There must be a concentration gradient 2) There must be no barrier blocking the movement of particles.

What is a concentration gradient? The difference in concentration between a region of high concentration and a region of lower concentration. Does this picture illustrate a concentration gradient?

What do we mean by a barrier? Will diffusion take place? YES Will diffusion take place now? NO The particles must be free to move down their concentration gradient in order for diffusion to occur.

Does diffusion take place across the cell membrane? Yes, the cell is: Selectively Permeable

Why do some things get through the cell membrane? Small molecules are more likely to get through the cell membrane compared to big molecules

Cell Membranes are: Selectively Permeable A selectively permeable membrane allows some substances to cross the membrane more easily than others and blocks the passage of other substances altogether.

8) What is facilitated diffusion? transport proteins help move materials from high to low concentration

9) What is the main job of the cell membrane? HOMEOSTASIS & TRANSPORT Cell membranes helps organisms maintain _____________ by controlling what substances may enter or leave cells To stay alive, a cell must exchange materials such as food, water, & wastes with its environment Blank = homeostasis