Warm-Up organelles 11/8/11 Why would plants need to have both chloroplasts and mitochondria? (Look at function for each) Have out animal and plant drawings to be stamped

Cell Membranes vs. Cell Walls  Cell Membranes regulate what comes into and comes into and out of cells out of cells  Cell Walls provide provide protection and protection and support for support for the cell the cell

Phospholipids make up cell membranes Polar “head” that is attracted to water Non-polar “tails” that are not attracted to water but are attracted to other phospholipid tails

Phospholipids make up cell membranes

Water molecules Water Polar head faces out towards water because of the attraction Nonpolar tails face inward so they are protected from water

Electron micrograph of cell membrane Inside cell layer Outside cell layer

Membranes are picky!!!  Membranes are semi-permeable because they only let certain molecules through  Small and non-polar molecules can pass through easily (water, oxygen, carbon dioxide)  Large and polar molecules cannot pass through without help (starch, glucose, proteins, amino acids, ions)

Diffusion and Osmosis Diffusion- The movement of particles from a region of higher concentration to a region of lower concentration, caused by the random motion of particles. Osmosis- The diffusion of water across a semi-permeable membrane towards the side with higher solute concentration.

Why does osmosis happen? Two factors cause osmosis: 1.A semipermeable membrane allows water molecules to move back and forth through the membrane, but not solute molecules 2.Water molecules “stick” temporarily to any dissolved solute molecules. As a result, water molecules spend more time and accumulate on the side of the membrane with the higher concentration of dissolved solutes.

Solutions  Solute- the substance dissolved in a solution  Solvent- the substance in which a solute is dissolved  Example In a solution of salt dissolved in water: Salt is the solute; water is the solvent

Types of Solutions  hypertonic solution- a solution with a higher solute concentration than what it is compared with.  hypotonic solution- a solution with a lower solute concentration than what it is compared with.  isotonic solution a solution with an equal solute concentration to what it is compared with.

Visual Examples Solution is hypotonic to cell. Cell is hypertonic to solution. Solution is hypertonic to cell. Cell is hypotonic to solution. Solution is isotonic to cell. Cell is isotonic to solution.

Facilitated diffusion The movement of molecules across a cell membrane from an area of higher concentration to an area of lower concentration with the help of a carrier protein. This transport does NOT require energy to happen. Moving large molecules.

Passive transport Passive transport happens spontaneously across the cell membrane. It does NOT require any cellular energy (ATP) because molecules move DOWN their concentration gradients (from high to low concentration). There are two types of passive diffusion: 1.Simple diffusion: molecules pass directly through the lipid bilayer. 2.Facilitated diffusion: molecules are too big to pass through the lipid bilayer. They bind to a carrier protein to diffuse across the membrane.

Passive transport Simple diffusion Facilitated diffusion Carrier protein Concentration Gradient

3 steps in facilitated diffusion 1. Particle binds to one side of carrier protein 2. Carrier protein changes shape 3. Particle diffuses to other side of membrane

Active transport The movement of molecules across a cell membrane from an area of low concentration to an area of higher concentration (“up” or “against” the concentration gradient). Active transport requires the use of energy (ATP).

Starch/Iodine Lab- Lab set up due Wednesday How does the size of molecules affect their diffusion across a semi-permeable membrane?How does the size of molecules affect their diffusion across a semi-permeable membrane? Create two experimental procedures to demonstrate question (pictures or words)Create two experimental procedures to demonstrate question (pictures or words) –Must keep solutions separate –Iodine solution (water with 10 drops of iodine) –Hypothesis is your prediction on what will happen Which molecule will moveWhich molecule will move Where will the color change take placeWhere will the color change take place

Homework:  Section 7.3 assessment questions, due Wednesday