Unit 4 Part B – Cell Membrane and Cell Transport

Vocabulary  Cell Membrane  Semipermeable  Lipid  Phospholipid  Phospholipid Bilayer  Hydrophobic  Hydrophillic  Passive Transport  Osmosis  Diffusion  Facilitated Diffusion  Homeostasis  Solute  Solvent  Concentration  Hypertonic  Hypotonic  Isotonic

Recap WHAT IS A CELL? - A COL - The basic unit all life - Surrounded by a membrane 2 Types of Cells 1. Prokaryotic 2. Eukaryotic Fundamental Differences?

PROK v EUK! Prokaryotic Cell -Most Common -No nucleus -First organisms on earth Eukaryotic Cell - Nucleus - Membrane bound organelles

Cell Membrane Functions - Protection - Regulation All cells have an outer plasma membrane that regulates not only what enters the cell, but also how much of any given substance comes in. “Gatekeeper” Separates a cell from its environment

Semi permeability: Cell membranes are semipermeable Also called selectively permeable - Some substances can pass - Some substances cannot pass

Cell Membrane and Homeostasis Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells Homeostasis- COL - Stable internal environment

Phospholipid Bilayer Function- Phospholipids are organized into a bilayer (2 layers) Arrangement- Phospholipid - Hydrophilic head Affinity to water Can interact with water - Hydrophobic tails Insoluble in water Does not interact with water

Lipid Structure Glycerol Fatty Acid

Lipid Bilayer The nonpolar regions ( hydrophobic) face the interior of the bilayer -No interaction with water The polar regions (hydrophilic) face outward where they interact with the water inside and outside of the cell.

Phospholipid Hydrophilic Hydrophobic

Water Insolubility Amino acids Sugars Oxygen Carbon dioxide Can dissolve in water Lipids do not dissolve in water

Soluble v Insoluble Soluble - A substance that can be dissolved Insoluble - Cannot be dissolved

Transport Passive Transport Passive- does NOT require Energy 1.Diffusion 2.Osmosis 3.Facilitated Diffusion

Passive Transport Every living cell exists in a liquid environment Tasked to keep its internal conditions constant (homeostasis) Cell membrane regulates what enters and leaves the cell Passive Transport - Diffusion

Diffusion Particles moving from an area of high concentration to an area of low concentration H  L

Diffusion Diffusion and the cell membrane Suppose a substance is present in unequal concentrations on either side of the cell membrane ◦If this substance can cross the membrane, its molecule will tend to move toward an area that is less concentrated until it is evenly distributed ◦Equilibrium  Even after this is reached, molecules in a solution will continue to move in both direction

Facilitated Diffusion RECAP - Cell membranes are build around a lipid bilayer - Most molecules that past through are small What happens when molecules cannot pass by themselves? - Enter: Facilitated Diffusion Proteins in the cell membrane act as carriers (channels) making it easier for certain molecules to pass Glucose can pass through these protein carriers These “channel” proteins help the diffusion of glucose across the membrane Hundreds of proteins have been found that allow particular substances to cross the membrane Specific

Facilitated Diffusion

Osmosis - Facilitated Diffusion - Movement of water through a semi permeable membrane - Water molecule move from an area of high solute concentration to an area of low concentration - H  L

Osmosis and Facilitated Diffusion - The inside of the bilayer is hydrophobic, causing water molecules to have a tough pass through - Channel proteins allow water to pass right through the bilayer

Osmosis P. 210 Fig 7-17 A - The barrier is semipermeable to water but not sugar - In the diagram: -More sugar on the right side than the left -Water will move towards the high concentration of sugar until equilibrium is reached