Cellular Transport: Part I Diffusion and Osmosis 8 classes until break!

Cellular Transport Overview Cells need to get things in and out of themselves How does a cell get things in, and out, if itself? What structure creates a barrier between the inside and the outside of a cell?

Diffusion All molecules have a certain amount of energy in them We often experience this energy in the form of kinetic energy and thermal energy What is kinetic energy? What is thermal energy? Do ALL molecules have this kind of energy?

Diffusion All molecules have a certain amount of energy This causes molecules to move around, resulting in a uniform distribution of molecules Molecules will diffuse until their concentration is balanced Say what? Let’s look at some demonstrations… Dye in water Scent in air

Diffusion Diffusion is: The net movement of molecules or atoms from a region of high concentration to a region of low concentration Demonstrations: Watch dye in water diffuse throughout the beaker What is the solvent? What is the solute? Scented molecules in air

Diffusion Molecules move from an area of higher concentration to an area of lower concentration

Diffusion How much energy did we have to exert to get the molecules to diffuse? How much energy do cells have to exert to get important molecules to diffuse? They take advantage of this natural phenomena! But, wait a second. Cells have a barrier between their insides and the outside world. Can things diffuse across this barrier? I am glad you asked! The cell membrane is SELECTIVELY PERMEABLE

Crossing the Cell Membrane To understand how cells move things in and out, you need to understand the cellular membrane What is a cell membrane made up of? Lipids, proteins, and carbohydrates Phospholipid bilayer Cell membranes only allow certain materials through Selectively permeable or Select permeability

Crossing the Cell Membrane Selectively Permeable to gases and small uncharged polar molecules What are some examples?

Facilitated Diffusion Diffusion across a membrane using carrier proteins. This is Still Passive Transport

Osmosis (because water is special…) Movement of a solvent (water) across a membrane toward a higher concentration of a solute (salt) Put another way…”water chases salt” Water will move across a semipermeable membrane to balance the concentrations of the solution Let’s look at a picture

Osmosis (because water is special…) 26 blue, 13 red vs 26 blue, 26 red 2:1 vs 1:1 26 blue, 13 red vs 52 blue, 26 red Maintains the 2:1 ratio

Solution Types Isotonic – Equal concentration in cell as compared to solution Hint: Iso means equal or same. Ex: Isosceles Triangle Hypotonic – Lower concentration of solutes in the solution than in the cell Hypertonic – Higher concentration of solutes in the solution than in the cell Remember….”water chases salt”…so which direction does water move? link

Passive Transport Review The movement of substance into and out of the cell without the use of energy is called passive transport Diffusion Food coloring diffusing in water on its own Scent traveling from one side of the room to the other Osmosis Water diffusing across membrane Facilitated Diffusion No energy required

Quiz your knowledge! When more water goes in through a cell membrane than out of it, the solution around the membrane is… If the solution surrounding a cell has lower concentration of solutes than the cell, water will move into a cell through osmosis, causing it to expand. What kind of solution is surrounding the cell? When the concentrations of solutes inside and outside a cell are the same (equal), the two environments are said to be….

Passive Cellular Transport Summary Three types: Diffusion, Facilitated Diffusion, Osmosis Application to the real world: Shipwreck Lab For Next Class: Homework is to create a study tool for vocabulary Vocabulary quiz next class Finish the Shipwreck Lab