Activating Question! Why does your home need to have walls?

Cellular Transport: The Movement of Materials

The Cell Membrane

Why does the cell need a membrane? Protect it from the environment Why does your home need walls? Decide what can go in or out

Plasma Membrane (aka the Cell Membrane) Phosopholipid Bilayer Called the Fluid Mosaic Model Selectively Permeable (or semi-permeable) What does this mean? (on next slide)

Why does the cell need a membrane? The cell membrane … Separates and protects cells from the outside environment Decides what can enter or exit the cell

What it’s made of… Membranes are made of a phospholipid bilayer (bi = two)

Phospholipids Phospholipid composed of hydrophobic tail and hydrophilic head 1. Phosphate head Hydrophilic – water “loving” 2. 2 fatty acid tails Hydrophobic- water “fearing”

WATER WATER Phospholipid Bilayer To keep the hydrophobic lipids away from water, phospholipids form a two-sided bilayer Plasma membrane WATER WATER

Fluid Mosaic Model The membrane also contains cholesterol, and proteins (with carbohydrate chains attached) Cholesterol keeps the lipids from sticking together Proteins move molecules across the membrane – carbohydrate chains help send signals/messages in cell interaction

Fluid Mosaic Model The membrane is not this simple! Fluid Mosaic Model

Checkpoint! How is the cell membrane like the walls of a house?

Checkpoint! A – Thumbs up & B – Thumbs down Which part of this molecule is polar and hydrophilic: A or B? Which part of this molecule is in the middle of the bilayer: A or B? A B

Checkpoint! Why must the membrane be a bilayer?

Activating Question! I plug in a Glade Plug-In at the front of the room… Who will smell it first: the people at the back of the room or the people at the front of the room? Will the people at the back of the room eventually smell it?

Selectively Permeable Only certain things can pass through the membrane Cells want to maintain homeostasis, stable internal conditions despite changes in its environment

Dynamic Equilibrium Diffusion occurs so that there is an equal concentration of particles on both sides of the membrane

Passive (no energy) Active Types of Transport Passive (no energy) Active (requires energy)

Passive Simple Diffusion Osmosis Passive Transport Passive Simple Diffusion Osmosis Facilitated Diffusion Movement of materials from that does not require energy (ATP)

High Concentration Low Concentration

What is happening here???

Types of diffusion: Simple (diffusion) – diffusion across cell membrane Facilitated diffusion - On next slide Osmosis – the diffusion of water

Simple Diffusion The passive movement of material straight through the cell membrane from an area of high concentration to an area of low concentration Concentration- the amount of solute in a solution (ex. Salt in water)

Facilitated Diffusion Diffusion of polar, hydrophilic particles that is helped by proteins in the membrane

Facilitated Diffusion Polar and hydrophilic molecules cannot move through lipids, so they move through proteins The molecules are still moving from high concentration to low concentration Still passive transport that does NOT require energy but does require the use of proteins in the membrane . .

Diffusion vs. Facilitated Diffusion

Factors affecting diffusion Concentration—diffusion always goes from high concentration to low concentration Concentration gradient: when there is an uneven distribution of molecules (concentration) across the membrane Temperature—the higher the temperature, the faster diffusion occurs Molecular Size—the bigger the molecule, the longer diffusion takes

Checkpoint! Put 1 finger up for A. Put 2 fingers up for B. Through diffusion, in which direction do particles move: A- high concentration low concentration B- low concentration high concentration

Checkpoint! What is the end result of diffusion?

Checkpoint! Will diffusion occur faster in boiling water or ice water?

Active Transport Movement of materials from low concentration to high concentration Moves through a protein pump that requires energy in the form of (ATP) Molecules move against the concentration gradient

Sodium-Potassium Pump Mechanism of active transport that moves potassium ions (K+) into and sodium ions (Na+) out of the cell

Checkpoint! Through active transport, in which direction do particles move: A- high concentration low concentration B- low concentration high concentration

Checkpoint! In order to move Na+ and K- through the membrane, what is the energy that must be used?

Endocytosis Process by which a large substance enters a cell without passing through the membrane. The substance enters through the formation of vesicle from the membrane

Phagocytosis & Pinocytosis Phagocytosis (Cell eating) - The process of membrane folding that enables cells to bring “food” into the cell EX: White blood cells ingest bacteria Pinocytosis (Cell drinking) - The process of membrane folding that enables cells to bring “water” (extracellular fluids) into the cell

Exocytosis Process of moving particles out of a cell using extensions of the cellular membrane how wastes are excreted from cells Intracellular vesicle moves to plasma membrane and fuses with it to release wastes

Activating Question Can you drink too much water? Explain.

YES! SACRAMENTO, Calif.- A woman who competed in a radio station’s contest to see how much water she could drink without going to the bathroom died of water intoxication. Jennifer Strange, 28, was found dead in her suburban Rancho Cardova home hours after taking part in the “Hold Your Wee for a Wii” contest in which a radio station promised a Nintendo Wii video game system for the winner.

Hyponatremia http://www.youtube.com/watch?v=WBXNCp dBFqQ Drinking too much water is called water intoxication, or hyponatremia, which means that your blood is too diluted and does not contain enough salt. Without the right balance of salt and water, your brain cells swell and burst, leading to death! http://www.youtube.com/watch?v=WBXNCp dBFqQ How does your body maintain balance?

Osmosis The diffusion of water through a selectively permeable membrane

Concentration Gradient A difference in concentration on opposite sides of the cell This makes diffusion and osmosis possible!

Osmosis-another look… Tonicity – A measure of the solute concentration in a solution

Hypertonic Solution Higher concentration of solute outside of the cell than inside The water moves out of the cell into the solution, causing the cell to shrink

Hypotonic Solution Higher concentration of solute inside the cell than outside the cell Water moves from the solution into the cell, causing it to swell or burst (lysis) Beneficial for plant cells – causes turgor pressure. In a hypotonic solution plants are turgid

Isotonic Solution Equal concentration of solute on both sides of the cell Water moves freely in to and out of the cell to maintain homeostasis.

Types of Solutions http://tonicity

Why doesn’t the plant cell undergo lysis?

Effect of Osmosis on Cells Practice In your table, draw what your cell would look like in each case. Use arrows to indicate the direction of water flow Effect of Osmosis on Cells Animal Cell Solution Before After Isotonic Hypotonic Hypertonic

Explain what is happening in this cartoon…

Observations! Take observations and draw the cells at the end of the video! Red Blood Cells in Hypotonic Solution: http://www.youtube.com/watch?v=EA_ss8ZkjAM Red Blood Cells in Hypertonic Solution: http://www.youtube.com/watch?v=IRQLRO3dIp8&feature=fvwrel

Clicker Quiz Time! 1. If you soak your hands in dishwater, you may notice that your skin absorbs water and swells into distinct wrinkles. This is because your skin cells are ____________ to the __________ dishwater. a. hypotonic, hypertonic b. hypertonic, hypotonic c. hypotonic, hypotonic d. isotonic, hypotonic e. hypertonic, isotonic

2. You decide to buy a new fish for your freshwater aquarium 2. You decide to buy a new fish for your freshwater aquarium. When you introduce the fish into its new tank, the fish swells up and dies. You later learn that it was a fish from the ocean. Based on what you know of tonicity, the most likely explanation is that the poor little fish went from a(n) _____________ solution into a(n) ____________ solution. a. isotonic, hypotonic b. hypertonic, isotonic c. hypotonic, hypertonic d. hypotonic, isotonic e. hypertonic, hypotonic

The concentration of solutes in a red blood cell is about 2% The concentration of solutes in a red blood cell is about 2%. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions? a. a hypertonic sucrose solution b. a hypotonic sucrose solution c. a hypertonic urea solution d. a hypotonic urea solution e. pure water

Sea water is dangerous to drink because… a. one cup of sea water contains enough sodium to poison you b. sea water is hypertonic to your body tissues and drinking it will cause you to lose water by osmosis c. sea water is isotonic to your body fluids and you will absorb too much water, causing your cells to burst d. the salt causes hypertension and you will promptly die of a stroke e. it contains toxic levels of iodine