1.Define a selectively permeable membrane 1.Using Model 1 and 2, what types of molecules can pass through a cell membrane? 1.What are the components of a cell membrane? (model 2)

Cell Membranes Structure and Transport: Chapter Vocab: -Phospholipid Bilayer -Semi-permeable -Passive transport -Diffusion, Facilitated Diffusion, Osmosis -Hypertonic, hypotonic, isotonic -Plasmolysis -Turgidity -Active transport -Endocytosis -Exocytosis

What cellular structures do prokaryotic and eukaryotic cells have in common? All Cells Have a Cellular Membrane

Cellular Membrane Functions Controls what enters and exits the cell Maintains and internal Balance (homeostasis) Provides protection and support for the cell

Structure of Cell Membrane Phospholipid Bilayer = 2 Layers of Phospholipids: – Phosphate head Polar/ Hydrophilic ( water loving) – Fatty Acid Tail non-polar/hydrophobic (water fearing)

Since there is water on the inside and outside of the cell, the water hating lipids hide in the middle of the membrane Polar heads love water & dissolve. Non-polar tails hide from water.

Fluid Mosaic Model The Cell Membrane Also Contains: -Proteins: transport materials and assists in chemical reactions -Cholesterol: helps maintain membrane flexibility/Fluid -Carbohydrate Chains: allows the cell to be recognized by other cells m/watch?v=Qqsf_UJcfBc

Membrane Transport: Selective Permeability Some molecules can pass freely - Small non-polar molecules -Diffusion Some Molecules need the help of Transport Proteins -Polar molecules (glucose) -Larger molecules (starch) -Charged ions (Na+, K+) Transport Protein

Label: 1.Phosphate Head 2.Lipid tail 3.Polar/ hydrophilic region 4.Non-polar hydrophobic region 5.Cholesterol 6.Transport Proteins

concentration gradient. 1.When the concentration of particles on one side of a membrane is higher than on the other, we call this a concentration gradient. 11/26/ “down the gradient.” 2. When this gradient exists, particles naturally move from high to low which we call moving “down the gradient.” Diffusion and a Membrane

Types of Cellular Transport Passive Transport -Cell does NOT use energy -High to Low Active Transport -Cell does use energy - Low to High high low This is gonna be hard work!! high low Weeee!!! Animations of Active Transport & Passive TransportAnimations

Passive Transport DOES NOT USE ENERGY Molecules spread out from an area of high concentration to an area of low concentration 3 Types – Diffusion – Facilitated diffusion – Osmosis

Passive Transport: 1. Diffusion 1.Diffusion: random movement of particles from an area of high concentration to an area of low concentration. (High to Low) Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-Note: molecules will still move around but stay spread out. Small non-polar molecules that can pass freely across the cell membrane Simple Diffusion AnimationSimple Diffusion Animation

2. Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane a.Transport Proteins are specific – they “select” only certain molecules to cross the membrane b.Transports larger or charged molecules c. HIGH TO LOW Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) Passive Transport: 2. Facilitated Diffusion Carrier Protein AB

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

Simple vs. facilitated diffusion 11/26/201519

3.Osmosis: diffusion of water through a selectively permeable membrane Water moves from high to low concentrations Osmosis Osmosis animation Passive Transport: 3. Osmosis

Effects of Osmosis on Life Osmosis- diffusion of water through a selectively permeable membrane Water is so small and there is so much of it the cell can’t control it’s movement through the cell membrane. Water moves freely through pores. Solute (green) to large to move across.

Hypotonic Solution Hypotonic: The solution has a lower concentration of dissolved particles 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)! Osmosis Animations for isotonic, hypertonic, and hypotonic solutionsOsmosis

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

Isotonic Solution Isotonic: The concentration of solutes in the 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) Osmosis Animations for isotonic, hypertonic, and hypotonic solutionsOsmosis

“Tonic” “Tonic” refers to the dissolved materials, not the water. 11/26/ Hyper- means a LOT of dissolved particles. Iso- means the SAME amount of dissolved particles. Hypo- means a LITTLE bit of dissolved particles. Dissolved particles such as a salt like NaCl. Key: Water.

What type of solution are these cells in ? A CB HypertonicIsotonicHypotonic

Question: Question: What would happen to a Plant cell placed into a Hypotonic solution? The Plant cell would swell, but it’s cell wall would protect it from bursting. turgid We refer to this type of cell as turgid. This allows plants to stand up straight. 11/26/201527

How Organisms Deal with Osmotic Pressure Paramecium (protist) removing excess water videoParamecium (protist) removing excess water video Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called tugor pressure. 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.

Types of Cellular Transport Passive Transport cell doesn’t use energy Active Transport cell does use energy high low This is gonna be hard work!! high low Weeee!!! Animations of Active Transport & Passive TransportAnimations

Active Transport cell uses energy (ATP) 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 1. Protein Pumps - transport proteins that require energy to do work Example: Sodium / Potassium Pumps are important in nerve responses. Sodium Potassium Pumps Sodium Potassium Pumps (Active Transport using proteins) Protein changes shape to move molecules: this requires energy!

Types of Active Transport 2. Endocytosis: 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!

Endocytosis

Types of Active Transport 3. Exocytosis: taking bulky material out of a cell Uses energy Molecules are packaged in a vesicle This vesicle fuses with cell membrane Contents are released Hormones or wastes released from cells