The Cell Membrane; Active & Passive Transport Chapter 7.3 The Cell Membrane; Active & Passive Transport

Diffusion Molecules tend to “spread out” Move from an area of high concentration to low concentration Requires no energy

Diffusion = The movement of molecules from an area of high concentration to an area of low concentration

Equilibrium

What’s this have to do with cells What’s this have to do with cells? Think about it…cells are like a nation Cells need things like a nation needs things… Exports, imports Has borders Why may a cell need materials to leave or enter a cell? How might this occur?

Cell Membrane Function: the GATEKEEPER 1) 2) 3)

Cell Membrane Structure Characteristics:

Cell Wall Found in most prokaryotes and some eukaryotes (plants, fungi, algae) Main function is support

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

Passive Transport (HighLow) cell uses no energy molecules move randomly Molecules spread out from an area of high concentration to an area of low concentration. (HighLow) Three types:

3 Types of Passive Transport Diffusion Facilitated Diffusion – diffusion with the help of transport proteins Osmosis – diffusion of water

Diffusion In a cell: - cytoplasm a solution of many different substances dissolved in water. As you know: -In any solution, solute particles tend to move from an area where they are more concentrated to an area where they are less concentrated.= Diffusion Diffusion---- the driving force behind the movement of many substances across the cell membrane.

Passive Transport: 1. Diffusion Simple Diffusion Animation Passive Transport: 1. Diffusion Diffusion: random movement of particles from an area of ______ concentration to an area of _______ concentration. (__________________) Diffusion continues until all molecules are evenly spaced (equilibrium is reached)- Note: molecules will still move around but stay spread out. http://bio.winona.edu/berg/Free.htm

7-15 diagram pg 209 Discuss with a friend and DRAW: What would be different in 7-15 if the high concentration of solutes had been inside the cell to start with?

Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) Passive Transport: 2. Facilitated Diffusion A B 2. Facilitated diffusion: diffusion of specific particles through transport proteins(protein channels/carriers) found in the membrane Transport Proteins are specific – they “select” only certain molecules to cross the membrane Transports larger or charged molecules Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) Carrier Protein http://bio.winona.edu/berg/Free.htm

Passive Transport: 2. Facilitated Diffusion Glucose molecules Cellular Transport from a High High Concentration Channel Proteins animations Cell Membrane to a Low Concentration Protein channel Low Transport Protein Through a  Go to Section:

Osmosis: A Type of Facilitated Diffusion Inside of a cell’s lipid bilayer is hydrophobic—or “water-hating.” water has a hard time getting through. Water channel proteins, known as ______________________ allow water to pass right through them. This movement of water is an extremely important biological =

Passive Transport: 3. Osmosis Osmosis animation 3.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.

Rule for Osmosis: Water will get sucked to wherever there is a higher concentration of salt.

Osmosis = The diffusion of water across a selectively permeable membrane ONLY THE WATER is moving.

How Osmosis Works Barrier below is permeable to water but not to sugar. -water molecules can pass through the solute, sugar, cannot.

How Osmosis Works More sugar molecules on the The concentration of water is __________________________ where more of the solution is made of sugar.

How Osmosis Works There is a net movement of water into the compartment containing the concentrated sugar solution. Water will tend to move across the barrier until equilibrium is reached. At that point, the concentrations of water and sugar will be the same on both sides.

How Osmosis Works When the concentration is the same on both sides of the membrane, the two solutions will be ______________ which means “same strength.”

Osmotic Pressure The net movement of water out of or into a cell produces a force known as osmotic pressure. = the force created by the net movement of water through a cell membrane.

Isotonic Solution iso=same Isotonic: The concentration of solutes in the solution is __________________ concentration of solutes inside the cell. Result: Water moves equally in both directions and the cell remains same size!

Isotonic

Hypotonic Solution Hypo=less Hypotonic: The solution has a _______ concentration of solutes and a __________ concentration of water than inside the cell. (_______solute; _______water) Result: Water moves from the solution to inside the cell: Cell Swells and bursts open

Hypotonic

Hypertonic Solution hyper = more Hypertonic: The solution has a ________ concentration of solutes and a ________ concentration of water than inside the cell. (_______ solute; ________ water) shrinks Result: Water moves from inside the cell into the solution: Cell shrinks

Hypertonic

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

How Organisms Deal with Osmotic Pressure Paramecium (protist) removing excess water video Bacteria and plants have cell walls that prevent them from over-expanding. Pressure can damage the cell wall though. A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding. Salt water fish pump salt out of their specialized gills so they do not dehydrate. Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.

Passive Transport Review Requires no energy Diffusion Osmosis = Diffusion of water Facilitated Diffusion: carrier proteins “help” molecules across the membrane like a tunnel

Active Transport (Low  High) cell uses energy actively moves molecules to where they are needed Movement from an area of low concentration to an area of high concentration (Low  High) Three Types:

Types of Active Transport Sodium Potassium Pumps (Active Transport using proteins) Protein Pumps – Example: Sodium / Potassium Pumps are important in nerve responses. Protein changes shape to move molecules: this requires energy!

Active Transport Small molecules pumped into or out of cell by transport proteins on the cell membrane. Transport goes against a concentration gradient Requires cellular energy (ATP)

Types of Active Transport 2. _________________: taking bulky material into a cell Uses energy Cell membrane in-folds around food particle “cell eating” forms food vacuole & digests food This is how white blood cells eat bacteria!

Types of Active Transport 3. __________________Forces material out of cell in bulk membrane surrounding the material fuses with cell membrane Cell changes shape – requires energy EX: Hormones or wastes released from cell Endocytosis & Exocytosis animations

Molecular Transport A considerable portion of the energy used by cells in their daily activities is devoted to providing the energy to keep this form of active transport working. The use of energy in these systems enables cells to concentrate substances in a particular location, even when the forces of diffusion might tend to move these substances in the opposite direction.

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