Teacher Preparation • Slice a potato so the slices are approximately the same thickness • Place ½ the slices in a beaker of salt water & the other ½ in a beaker of distilled water. (Do 30 minutes ahead of class start so water movement happens) Around mid-morning prepare a second set of beakers for the afternoon classes. (Use plastic beakers or bowls) • Run off boot camp arrows and diffusion cards • Run off osmosis worksheet
Biology 4B Investigate and Identifycellular processes including: homeostasis, permeability, energy production, transportation of molecules, disposal of wastes, function of cellular parts, and synthesis of new molecules.
What Happened? • Your teacher will pass around two beakers containing cut up vegetables and water. Salt water is the liquid in one of the beakers. The other beaker contains distilled water. Feel the vegetables. • Are the vegetables firm or soft? • Compare the feel between the two bowls • What happened to cause this difference? We will discuss it in a few minutes.
The Beaker I am showing you contains water I will place a drop of food coloring in it. Please watch and try to explain what is happening We will revisit this later in the period. BEAKER
Each of the vegetable slices you felt is composed of thousands of cells that are bound together Each one of these cells is held together by a cell membrane or plasma membrane In your biology class, you learned that all living things are made of cells
Outside of cell Carbohydrate chains Proteins Cell membrane Inside of cell (cytoplasm) Protein channel Lipid bilayer Cell Membrane The Cell or Plasma Membrane Surrounds and Holds a Cell Together. It also controls what substances can enter or leave a cell.
In or Out? How is a window screen similar to a cell or plasma membrane? Read on to find out. 1.What are some things that can pass through a window screen? 2.What are some things that cannot pass through a window screen? Why is it important to keep these things from moving through the screen? 3. The cell is surrounded by a cell membrane, which regulates what enters and leaves the cell. Why is it important to regulate what moves into and out of a cell?
Like a screen the cell/plasma membrane is semi-permeable or selectively permeable Water NaCl Salt Starch Lugol’s Iodine C6H12O6 Glucose Inside Cell Outside Cell Which substances can go through the pores? Pores Answer: Water, Lugol’s, Glucose (Starch, Salt are too big!)
SOLUTIONS • Is a homogenous mixture of a solute in a solvent • Solute - molecule that is dissolved • Solvent - what dissolves the molecule • *Concentration-the amount of solute in the solvent (3% salt & 97% water)
Solution Examples: ½% Milk = .5% fat and 99.5% milk/water 1% Milk = 1% fat and 99% milk/water 2% Milk =2% fat and 98% milk/water
Kinetic Energy • Energy of Motion • Molecules are always in motion • Solids - slow • Liquids - medium • Gases-fast
Diffusion • Movement of a substance from high concentration to low concentration (kinetic energy) ( Ex: Diffusion of smoke, perfume etc in a room.)
Equilibrium-Discuss Beaker Demo • When the rate of particles into or out of an area is equal. (The particles do NOT quit moving but their net movement is zero)
Osmosis - movement of water from high concentration to low concentration Dialysis Tubing Bag Contains 10% Starch and 90% Water 20% Lugol’s Iodine 80% Water If the dialysis tubing bag is placed in the Lugol’s Iodine bowl what will happen? (The tubing has pores) Answer: Lugol’s Iodine will diffuse in the bag from high to low concentration, osmosis will occur and water will come out of the bag from high to low concentration but starch molecules are too big to pass through the bag.
Diffusion of Sugar and Osmosis of Water Movement from higher concentration to lower concentration
Osmosis & Diffusion Can Occur at the same time Which Substance will move and why? Distilled Water has no minerals; so it is 100% water The distilled water molecules will move by osmosis into the glucose solution; the glucose will diffuse into the distilled water. In both cases substances move from high to low concentration. This solution is 8% glucose; the rest is water (92%)
Boot Camp Cards & Arrows Class Participation
Perfect Situation: If a cell with 3% salt solution is in an equal solution of 3% salt, then equilibrium is reached and concentrations are equal. Water goes in & out of cell at the same rate *Notice: normal appearance Water molecules still move but they move equally in and out of the red blood cells.
If a cell with 3% *salt solution is placed in a 10% salt solution outside the cell then water would leave the cell and the cell dehydrates and shrinks *Notice: shrunken appearance Water leaves cell
Problems with Osmosis If a cell with a 3% * salt solution inside the cell (97% water) is placed in distilled water (100% water), then it could lyse (or burst) Water goes in *Notice: swollen appearance
CONCENTRATION • Concentration-the amount of solute in the solvent The more concentrated a substance is, the faster it diffuses.
PARTICLE SIZE Particles with more mass move slower than those with less mass. In this picture a crystal of iodine (brown) and crystal of methylene blue (blue) were place on clear agar for 15 minutes. Which one diffused more? The iodine has less mass.
TEMPERATURE Atoms & Molecules movement increases with increased temperature In this previous slide it took 15 minutes for the diffusion to happen. This petri dish was placed on a hot plate and the iodine and methylene blue diffused in two minutes. Why?
WHAT HAPPENED? • Explain in terms of osmosis why the salt water vegetables felt limp? • Explain, in terms of osmosis, why the distilled water vegetables felt very turgid. (Hard) 99% H2O 1% salt 99% H2O 1% salt 80% H2O 20% Salt Salt Water 100% H2O Distilled Water
*Think about it! • A cucumber is normally 99% water and 1% salt. Explain what would happen and WHY, if: • The cucumber were placed in a solution of distilled water. (Distilled water is 100% water) • The cucumber were placed in a solution of 80% water & 10% salt. • The cucumber were placed in a solution of 99% water & 1% salt.
Practice Questions When a sea urchin egg is removed from the ocean and placed in freshwater, the egg swells and bursts. Which of these causes the water to enter the egg? A Coagulation B Sodium Pump C Active Transport D Osmosis
Practice Questions The picture shows a cell model and the solutions associated with it. In this situation the cell model will- A gain mass B shrink C increase in solute % D start to vibrate
Practice Questions Which of these best explain why a freshwater aquarium would be a dangerous habitat for saltwater fish? A The tissues of the saltwater fish would absorb too much acid B The organs of the saltwater fish would produce too much protein C The organ systems of the saltwater fish would consume too much energy D The cells of the saltwater fish would gain too much water