Diffusion Particles in a solution move from an area of more concentration to an area of less concentration. Particles must be small to cross the cell membrane. No proteins are required Sometimes channel proteins help No Energy is required. More concentration Less concentration

Diffusion Particles will move from an area of high (more) concentration to an area of low (less) concentration until EQUILIBRIUM is reached.

Equilibrium Equal amounts of solute on both sides of a membrane. Even when equilibrium is reached, particles will continue to diffuse in both directions, but the concentration won’t change.

Semi - Permeable Membrane Some substances can pass across and others cannot.

Osmosis Osmosis is the diffusion of water through a selectively permeable membrane. Small water molecules move from an area of greater water concentration (more pressure) to an area of lesser water concentration (less pressure). No proteins are required but they often help. Sometimes aquaporin proteins help. No Energy is required.

Osmosis Isotonic www.biologycorner.com/resources/osmosis.jpg

Potato Slice Set-up Procedure: Feel the texture of the potato slices. Record your observations in the data table on the worksheet. (You only need to fill in the gray boxes now because all potatoes should feel the same at the start of the experiment). Put one slice into a petri dish of distilled water, one slice into a petri dish of salt water and the leave the third slice in the tray exposed to air. Record the time in the data table below. Wait for one hour: You will be visiting the rest of the stations and finishing the notes during this time.

Distilled Water Salt water

Egg Osmosis Lab Observe the egg in the container labeled “observation egg.” You can pick the egg up but please be gentle. It will break! This egg has had the shell dissolved off in vinegar. What you are touching is the cell membrane of the egg. It is semi-permeable and thus will let some materials in and out of the cell but not all. Pick up an Egg Osmosis Lab worksheet and complete questions 1-7. Use the definitions on the slide to help you. Fill in the original circumferences provided in the data table. We will finish this lab tomorrow.

Egg without Shell

Eggs in different solutions

Types of Solutions Isotonic solution: Same strength The solute concentration is the same inside and outside the cell. Hypertonic solution: Above strength The solute concentration is higher in in the solution surrounding the cell than inside. Hypotonic solution: Below strength The solute concentration is lower in the solution surrounding the cell than inside.

Passive Transport Facilitated diffusion is the passive transport of materials transport proteins. Passive means that no energy is needed. Move from high concentration to low No ENERGY is required. The particles are too big for normal diffusion so they pass through protein channels in the membrane.

Facilitated Diffusion

Different types of proteins can help.

Active Transport Active Transport: Materials move against a concentration gradient. (Less concentration to more concentration) ENERGY!! (ATP) is required. Protein “pumps” use energy to change shape and push materials across the membrane. More concentration Less concentration Energy

Active (energy) vs Passive (no energy)

Active Transport by the Cell Membrane Endocytosis: a cell takes material into the cell by infolding of the cell membrane. No proteins needed because cell membrane folds to enter cell. Phagocytosis: cell-eating (food vesicles) Exocytosis: moving large molecules across the membrane out of the cell. Both require a lot of Energy!!!

Exocytosis – leaving the cell

Endocytosis – entering the cell