DNA Compare and contrast prokaryotes and eukaryotes with your groupmates Put away everything but a pen or pencil

When Finished with Quiz… Grab a computer for you and the person sitting next to you Log in – if it says you can’t shut off the computer, turn it on and try again Google “PHET simulations” and play around with one of the simulations until everyone is done

Osmosis/Diffusion Activity Work as partners – we’ll begin as a class

Activity 1 Start in one corner Try to move randomly- when you (Carefully) bump into somebody “bounce” the other direction What happens?

Diffusion We call this phenomenon diffusion Things naturally bounce off each other and spread apart – if they can We say things move from “high concentration” to “low concentration”

What does this have to do with cells? Lots of things enter and exit this cell by this process However, they must be able to somehow cross the membrane Cytosol

General Membrane Structure Phospholipids with proteins embedded in the membrane Different membranes have different proteins

Phospholipid Bilayer

Observation 1 Watch the water and oil, do they mix? What happens when we drop food coloring into the oil layer?

Hydrophilic and Hydrophobic Don’t Mix The inside of the membrane is hydrophobic (oily) Which means polar things will not mix well with it Ions will definitely not mix well

Membranes Keeps Cells Separate Most things are either too big to cross the membrane OR they are polar and won’t mix with the membrane Creates an internal environment different from the outside world (i.e. it has enzymes, proteins, sugars, ATP, NADH, FADH etc. floating around)

Simple Diffusion Very small hydrophobic (non-polar) molecules can simply slip between the membranes and cross the hydrophobic layer Water is small enough that some of it can slip through

Facilitated Diffusion Other small molecules need to move through a protein channel (small, polar or ionic compounds)

Observe the Facilitated Diffusion What will happen when we put a channel in the membrane?

Concentration Gradient High Concentration Low Concentration

Equilibrium / No Concentration Gradient No net change in concentration. Molecules still move but on average the concentrations stay the same Medium Concentration

Facilitated Diffusion – 2 molecules

What if We Want to Move Things Against the Gradient? Active Transport! We must invest energy to “pump” molecules

Review Small, non-charged molecules can simply diffuse Small, polar or charged molecules can pass through a protein Energy must be invested to move things against the gradient

Endo/Exocytosis Big things must enter through endocytosis and form a vesicle Big things must exit by exocytosis, where the vesicle becomes part of the plasma membrane

Selective Permeability Membranes control what gets in and what gets out of the cell Protein channels or pumps can be opened and closed

Osmosis Special name for diffusion of water When molecules can’t diffuse, water does Water diffuses towards the more concentrated side until the concentrations are balanced* *or another force is applied