Warm-up Turn to page 178 in your textbook and answer questions 1 through 4.

Chapter 8.1 Cellular Transport

Let’s review what you already know 1. Why is the plasma membrane said to be selectively permeable? 2. Define diffusion. 3. What is a solution? What is the solvent and solute of a solution? 4. Define concentration gradient.

Section Objectives Explain how the processes of passive and active transport occur and why they are important to cells. Predict the flow of water in a hypotonic, hypertonic, or isotonic solution.

Osmosis: Diffusion of Water Osmosis is the diffusion of water through a membrane The plasma membrane does not limit the passage of water through the membrane Water moves to reach equal concentrations on both sides of the membrane

Osmosis: Diffusion of Water Osmosis is controlled by the concentration gradient If two different solutions are separated by a selectively permeable membrane that allows water only to pass through, water will flow to the side of the membrane where the water concentration is lower (high to low)

Osmosis: Diffusion of Water

Isotonic Solution – A solution where the concentration of dissolved substances is the same as the inside of the cell No net water movement

Osmosis: Diffusion of Water Hypotonic Solution – A solution where the concentration of dissolved substances is lower in the solution outside of the cell than inside of the cell Net water movement into the cell

Osmosis: Diffusion of Water Hypertonic Solution – A solution where the concentration of dissolved substances outside of the cell is greater than inside of the cell Net water movement is outside of the cell

Osmosis: Diffusion of Water The thing to remember about osmosis is that water always moves from an area of high concentration to low concentration until balanced Osmosis can affect the shape of a cell as well, as seen in the pictures on the next slide, plant cells can with stand greater change than animal cells

Isotonic Solution - the cell is stable Hypotonic Solution - the cell has gained water Hypertonic Solution - the cell has lost water

Warm Up Turn to page 218 of your textbook and answer questions 6 & 7. What do you think will happen when a freshwater paramecium is placed in salt water?

Passive Transport There are two types of cellular transport – Passive transport – movement of particles across a membrane without the use of energy – Active transport – movement of particles across a membrane which requires energy

Passive Transport Passive transport moves with the concentration gradient (from high to low) Facilitated diffusion is diffusion through a membrane with the help of a transport protein

Passive Transport Passive transport includes: Diffusion/Osmosis Facilitated Diffusion by a channel protein Facilitated Diffusion by a carrier protein **Concentration Gradient **

Active Transport Active transport requires energy because it moves against the concentration gradient (from low to high concentration)

Active Transport Active transport also includes: – Endocytosis – engulfing large particles – Exocytosis – expulsion of large particles

Section Review 1. What controls the diffusion of water through a membrane? 2. Which way will water move in a hypertonic solution? A hypotonic solution? 3. Distinguish between active and passive transport. Give examples.