The Cell Membrane What did you observe about

The Cell Membrane What did you observe about membrane behavior from this video?

Movement Across Membranes Cell membrane is selectively permeable: Look at the membrane model again. How 4. Macromolecules (starches) 3. Large, nonpolar molecules (glucose) 2. soluble molecules (water) 1. Small, non-lipid soluble molecules do (hydrocarbons) you think the following materials get in/out? :

Effect of Phospholipid Structure

Fluidity Watch the membranes – are they rigid? If not, how do they move? Rate molecules move within & across membranes depends on • temperature • structure of hydrocarbon tails in bilayer

Membrane Transport

Solute Movement across Lipid Bilayers • Materials move across membrane in different ways. 1. Passive transport does not require energy input 2. Active transport energy required for substances to cross the membrane. • Small molecules and ions in solution are called solutes, have thermal energy, and are in constant, random motion. • Differences in solute concentration across the

Goal? Reaching Equilibrium! One way to do this is diffusion – direct movement of solutes from areas of high to low concentration NO energy required = PASSIVE transport

Osmosis • Does water move towards high solute concentration? Low solute concentration? • Does water concentration move from high to low or low to high concentration?

Hyper-, Hypo-, & Isotonic

Let’s practice

Hyper-, Hypo-, or Isotonic? (in your notes) • Use arrows to show the direction of water movement into or out of each cell.

Label the Plant Cell • What type of solution are they in?

Label the Red Blood Cells Why should you worry about this? • What type of solution are they in?

Membrane Proteins Affect Ions and Molecules • Transmembrane proteins that transport molecules are transport proteins. • THREE broad classes of transport proteins; each affects membrane permeability: 1. Channels 2. Carrier proteins or transporters 3. Pumps

Movement affects gradient, affects continued movement

Facilitated Diffusion vs. Pumps 1. Facilitated diffusion – PASSIVE transport of substances using specific channel proteins Ex: GLUT-1 transport protein increases permeability of membrane to glucose 2. Protein Pumps – ACTIVE transport using ATP to move substances against concentration gradient Ex: Sodium/Potassium Pump transports Na+ & K+ against electrochemical gradient

Active Transport: Pumps This can set up a gradient that “switches” on the transport of other materials. This is called secondary transport or cotransport.

Active Transport: Endo/Exocytosis

Summary of Membrane Transport • Give examples of types of transport across the membrane. • Diffusion and facilitated diffusion are forms of ____transport and thus move materials down their concentration gradient and ____require an input of energy. • ______transport moves materials against their concentration gradient and _______energy provided by _____or an electrochemical gradient.

Homework Scenario 1. Intraveneous solutions must be prepared so they are isotonic to red blood cells. A 0. 9% salt solution is isotonic to red blood cells. a. Explain what would happen if you placed a red blood cell in a solution of 99. 3% water and 0. 7% salt. b. Explain what would happen if you placed a red blood cell into a solution of 90% water and 10% salt.

2. What would happen to a cell if placed in the following solutions? Explain in detail and illustrate. a. Hypotonic b. Isotonic c. Hypertonic