PowerPoint Learning Quest

Biology 9Unit 5: Cell Biology (Part 2)

Created by: Jeff Wolf and Mike Graff

Objectives: After completing this Learning Quest the student

will…Describe the function of a cell membrane.Explain the step-by-step process of cell transport.Describe, in detail the processes of selective permeability, passive transport, diffusion, osmosis, facilitated diffusion, passive transport, and active transport.

Directions1. Follow the instructions in

the Anticipation Guide found in this PowerPoint Presentation.

2. Follow the instructions and answer all questions found in the Learning Guide.

3. Follow the instructions in the Conclusion Guide.

4. ALL THREE GUIDES CAN BE FOUND IN THIS LEARNING POWERPOINT QUEST.

Anticipation Guide (Page 1)

The focus of this unit will be on how cells receive nutrition and dispense of waste through the very complex cell membrane. First let’s review the function of the cell membrane and how molecules move into and out of the cell via the cell membrane.

Anticipation Guide (Page 2)

To understand the constant movement of molecules into and out of the cell through the cell membrane one must first understand two concepts: selective permeability and diffusion.

Anticipation Guide (Page 3)

Selective permeability means that a membrane allows some substances to cross over more easily than others. Selective permeable membranes such as a cell membrane can “select” which molecules it will allow into and out of the cell and which molecules it will not allow into and out of he cell. Much of what can diffuse across the plasma membrane is based upon the size and chemical makeup of the molecule.Transport proteins, found built into the cell membrane assist in the movement of molecules through passive and active transport. The cell membrane along with the transport proteins work together to in a process called diffusion. An example of a transport protein.

Anticipation Guide (Page 4)

Diffusion is the tendency for molecules of a substance to spread out into any available space. Molecules are often wandering randomly when energy called thermal motion or heat is applied. However, a diffusion of a population of molecules can be directional.For example, look at the diagram (a) to the right. Now imagine that a membrane separating pure water from a solution a food coloring dye mixed with water. We first must assume that the membrane is permeable to the dye molecules. Therefore, the membrane will allow dye molecules through the membrane in both directions. The dye molecules will move into the other side of the membrane until there is an equilibrium or an equal mount of dye molecules on both sides of the membrane. Don’t forget that molecules are in a constant state of motion.

Anticipation Guide (Page 5)

Simply put, a substance when it comes into contact with a membrane will diffuse from an area that is more concentrated to an area which is less concentrated. This diffusion across a membrane is called a passive transport.Next let us move onto the Learning Guide to find out the specific operations of the cell membrane.

Learning Guide (Page 1) As mentioned, in the Anticipation Guide, throughout the thin layer of the cell membrane are found protein transports that assist in the diffusion process. One type of transport is known as passive transport. This particular type of transport is passive because the cell does not used any energy in order for the diffusion of molecules to take place. Although, the membrane does not exhibit any energy during passive transport, selective permeability still takes place.

Learning Guide (Page 2)The passive transport of water molecules across a selectively permeable membrane is called osmosis. As seen in the diagram to the left, the membrane is permeable to water but not to the solute. Therefore, the water within the tube does not transfer equally because the solution to the left of the membrane is hypotonic and the solution to the right hypertonic. Let us exam the difference between these two types of solutions.

Learning Guide (Page 3)A hypotonic solution is a solution with a low solute concentration and a high water concentration.A hypertonic solution has a high solute concentration. As seen in the diagram, the hypotonic solution has a low solute concentration and a higher water concentration.Thus, water will diffuse across the membrane from the hypotonic solution to the hypertonic solution to establish and equilibrium. This is the process of osmosis.

Learning Guide (Page 4) When a cell is said to have an equal concentration of solute on both sides of the cell membrane that solution is said to be isotonic. Refer to page 77 – Figure 4.26It is very important for a animal cell or plant cell to balance water gain or loss. When a cell balances the input and output of water equally, it is said to have a Isotonic solution (a).When a cell has more water coming into through the membrane than leaving this cell has a hypotonic solution (b)Finally, when a cell has more water leaving through the membrane than coming into through the cell membrane, this cell has a hypertonic solution ( c ) .

Learning Guide (Page 5)Cell membranes not only have passive transports but also has active transports, as well.Active transports require energy from the cell in order to move molecules across the cell membrane. As seen in the diagram to the right. Active transports uses ATP, produced by the cell’s mitochondria, as an energy source to transport molecules across the membrane.

An example of an active transport transferring molecules across the membrane with the help of ATP

Learning Guide (Page 6) Over the past few slides we have talked about how small molecules enter and leave the animal or plant cell. Next we will talk about how larger molecules are transported into or out of your cells. This can be accomplished by two processes known as either exocytosis or endocytosis.

Learning Guide (Page 7)When the cell needs to obtain or release large molecules such as a protein; they do this through a process known as exocytosis or endocytosis. When the cell releases larger molecules it packages them into vesicles and moves them closer to the membrane. When the vesicle comes in contact with the cell membrane it opens its container and releases the molecule outside of the cell. This process is known as exocytosis (a).

Learning Guide (Page 8)When the cell needs to take larger molecules into the cell, a vesicle is formed around the molecule. The vesicle is then taken into the cell through a process called endocytosis (b).

Conclusion Guide (Page 1) The two types of Endocytosis include:

a. Pinocytosis – or “cellular drinking” where cells can gulp droplets of fluid.

b. Phagocytosis – or “cellular eating” where a cell engulfs a particle and packages it within a food vacuole

Conclusion Guide (Page 2)Exocytosis and Endocytosis: The movement of large molecules within your cells.

Work Citedhttp://micro.magnet.fsu.edu/cells/animals/images/plasmamembrane.jpghttp://www.usd.edu/~bgoodman/realcell.JPGhttp://www.cneccc.edu.hk/subjects/bio/album/Chapter4/images/PASSIVE_TRANSPORT.jpghttp://lhs.lps.org/staff/sputnam/Biology/U3Cell/endocytosis_1.png

After completing the test, move onto Unit #6.