3.4 Diffusion and Osmosis Somewhere on pg. 30 or 31 If the cell membrane was rigid (solid or hard), as opposed to fluid (oil or liquid like), explain why the membrane would no longer be selectively permeable.
The phospholipids would be unable to move to allow material in or out! 3.4 Diffusion and Osmosis If the membrane was rigid: The phospholipids would not be able to move from side to side or slide past one another The phospholipids would be unable to move to allow material in or out!
3.4 Diffusion and Osmosis Standard 1.a Students know cells are enclosed within a semipermeable membranes that regulate their interaction with their surroundings.
3.4 Diffusion and Osmosis KEY CONCEPT Materials move across membranes because of concentration differences.
3.4 Diffusion and Osmosis Solution: A homogenous mixture of two or more substances, which may be solids, liquids, or gases, or the combination of these. Ex: Salt water Solute: Substance dissolved in another substance Ex: Salt Solvent: Substance doing the dissolving (usually the substance present in the greatest amount) Ex: Water
Which one is the Solute? Solvent? Solution? Water Colored Water Food Coloring Solution Solvent Solute Air Nitrogen (78%) Oxygen, argon, CO2 (22%) Solution Solvent Solute
3.4 Diffusion and Osmosis Passive transport- the movement of molecules across a cell membrane without energy input from the cell There are two types of passive transport. 1. diffusion 2. osmosis
3.4 Diffusion and Osmosis Diffusion: is the movement of molecules in a fluid or gas from a region of higher concentration to a region of lower concentration.
3.4 Diffusion and Osmosis Diffusion: is the movement of molecules in a fluid or gas from a region of higher concentration to a region of lower concentration.
3.4 Diffusion and Osmosis Diffusion: is the movement of molecules in a fluid or gas from a region of higher concentration to a region of lower concentration.
Concentration gradient- the difference in the concentration of a substance from one location to another. Molecules diffuse down their concentration gradient
Diffusion Demonstration (Mini Lab) Materials: 2 Cups, Water, Dye, Salt,Graph Identify the solvent, solute, and solution for each demonstration Hypothesize what is going to happen when you drop the food coloring in the water. Salt in the water? Did your hypothesis match the results? Explain how these experiments demonstrated diffusion
3.4 Diffusion and Osmosis Osmosis is the diffusion of water molecules across a semipermeable membrane. Sugar molecules Water molecules
3.4 Diffusion and Osmosis There are three types of solutions. Same amount of solutes/water inside and outside cell = amounts of water enter and leave the cell Stays the same size! More solutes outside the cell More water inside the cell More water exits cell Shrinks! Less solutes inside the cell More water outside cell More water enters cell Expands!
Osmosis Demonstration (Mini Lab) Materials: 3 cups (labeled), 3 grapes, water, grape juice, sugar, and a scale Label each cup: Water, Sugar water, grape juice Hypothesize what is going to happen when you put a grape in each solution?
Weigh a grape- record its weight in the “Before the grape juice” box Place the grape in the grape juice cup Next partner, weigh a grape, record its weight in the “Before the water” box Place the grape in the water cup Next partner, weigh a grape, record its weight in the “Before the Sugar Water” box Place the grape in the sugar water Wait 24 hrs and record the weight of the grapes
Grapes after 24 hrs Dry off your first grape- be careful! Weigh your grape and record the results Repeat these steps for each of the remaining grapes (Don’t mix them up!) Did your hypothesis match the results? Explain how this experiment demonstrated osmosis
3.4 Diffusion and Osmosis Some molecules cannot easily diffuse across the cell membrane. Facilitated diffusion is diffusion through transport proteins.