Section Objectives Explain how the processes of diffusion

Section Objectives Explain how the processes of diffusion, passive transport, and active transport occur and why they are important to cells. Predict the effect of a hypotonic, hypertonic, or isotonic solution on a cell.

Today you will learn about 1. Passive Transport 2. Osmosis 3. Osmosis within the 3 types of solutions.

Osmosis: Movement of Water Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. In a cell, water always moves to reach an equal concentration on both sides of the membrane.

Osmosis: Movement of Water The movement of water across a selectively permeable membrane is called osmosis. Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis within a cell.

What controls osmosis? Unequal distribution of particles, called a concentration gradient, is one factor that controls osmosis. Before Osmosis After Osmosis . Selectively permeable membrane Water molecule Sugar molecule

Osmosis: Diffusion of Water Most cells whether in multicellular or unicellular organisms, are subject to osmosis because they are surrounded by water solutions.

Types of Cellular Transport Weeee!!! Passive Transport cell doesn’t use energy Diffusion 2. Facilitated Diffusion 3. Osmosis 1. high low Active Transport cell does use energy Protein Pumps 2. Endocytosis 3. Exocytosis 1. high This is gonna be hard work!! low

3 Types of Passive Transport 1. Diffusion – molecules move high to low. 2. Facilitative Diffusion – diffusion with the help of transport proteins. 3. Osmosis – Water moves high to low.

Passive Transport: 1. Osmosis: diffusion of water through a selectively permeable membrane. Water moves from high to low concentrations. • Water moves freely through pores. • Solute (green) too large to move across.

Effects of Osmosis on Life Osmosis- diffusion of water through a selectively permeable membrane. There are 3 types of solutions: Isotonic Hypertonic Hypotonic

Isotonic Solutions that contain the same concentration of solutes as the cytoplasm are called isotonic (or normal saline) solutions. There is no net movement of water either into or out of the cell. Cells maintain their normal shape. WATCH VIDEO OF BLOOD IN AN ISOTONIC SOLUTION

Isotonic Solution • Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Isotonic: The concentration of solutes in the external solution is equal to the concentration of solutes inside the cell. Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)

Cells in an isotonic solution(= concentrations) the concentration of dissolved substances in the solution is the same as the concentration of dissolved substances inside the cell. H 2 O Water Molecule Dissolved Molecule

Cells in an isotonic solution H 2 O Water Molecule Dissolved Molecule water molecules move into and out of the cell at the same rate, and cells retain their normal shape.

Cells in an isotonic solution A plant cell has its normal shape and pressure in an isotonic solution.

Hypotonic Solution A hypotonic solution contains less solute (thus, more water) than the cytoplasm of the cells. The water will move into the cells resulting in the swelling and lysis of the cells. WATCH VIDEO OF CRENATED RBCs SUBJECTED TO A HYPOTONIC SOLUTION

Hypotonic Solution • Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water) Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!

Let’s take a closer look! http: //www. coolschool. ca/lor/BI 12/un it 4/U 04 L 06/rbc. html

Cells in a hypotonic solution: dilute solution thus low solute concentration In a hypotonic solution, water enters a cell by osmosis, causing the cell to swell. H 2 O Water Molecule Dissolved Molecule

Cells in a hypotonic solution Plant cells swell beyond their normal size as pressure increases. (plants prefer this –it makes the leaves firm)

Hypertonic Solution A hypertonic solution is a solution that contains more (hyper) solutes than the cytoplasm of the cell. Has less water than the cell and water moves out of the cell. The cells shrink. WATCH VIDEO OF NORMAL RBCs SUBJECTED TO A HYPERTONIC SOLUTION

Hypertonic Solution • Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water) shrink s Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis/crenation)!

Cells in a hypertonic solution: concentrated solution, thus a high solute concentration In a hypertonic solution, water leaves a cell by osmosis, causing the cell to shrink H 2 O Water Molecule Dissolved Molecule

Cells in a hypertonic solution Plant cells lose pressure as the plasma membrane shrinks away from the cell wall. PLASMOLYSIS

Passive Transport When a cell uses no energy to move particles across a membrane passive transport occurs Particles go DOWN their concentration gradient. Diffusion & osmosis are passive transport. Plasma membrane Concentration gradient

Passive Transport by proteins Passive transport of materials across the membrane using transport proteins is called facilitated diffusion. Plasma membra ne Channel proteins Concentrati on gradient

Passive Transport by proteins Some transport proteins, called channel proteins, form channels that allow specific molecules to flow through.

Active Transport active transport : Movement of materials through a membrane against a concentration gradient and requires energy from the cell. Cellular energy Plasma membrane Carrier proteins Concentration gradient Cellular energy

How active transport occurs a transport protein called a carrier protein first binds with a particle of the substance to be transported. Each type of carrier protein has a shape that fits a specific molecule or ion.

Transport of Large Particles Endocytosis is a process by which a cell surrounds and takes in material from its environment. The material is engulfed and enclosed by a portion of the cell’s plasma membrane. resulting vacuole with its contents moves to the inside of the cell Exocytosis is the expulsion or secretion of materials from a cell. Endocytosis Exocytose

Study the diagram below. Which arrow shows the direction the solute molecules would move to achieve homeostasis?

If the membrane shown is permeable to molecules of X, but impermeable to molecules of Y, what will be the result of diffusion over time? A. Molecules of X on each side of the membrane will become equal in concentration. B. Molecules of Y on each side of the membrane will become equal in concentration. C. Molecules of X will increase in concentration on the right side. D. Molecules of Y will increase in concentration on the right side.

Cellular Transport Osmosis

What type of solution are these cells in? A Hypertonic B Isotonic C Hypotonic

Summary What is osmosis? Is osmosis considered passive or active transport? What are the 3 types of solutions involved in osmosis? 1. 2. 3.

How well did you do today? What is Osmosis? A. The movement of molecules. B. The movement of molecules from an area of high concentration to low concentration. C. The movement of water from a low concentration to a high concentration. D. The movement of water from a high concentration to a low concentration.