Lab Safety Biology 111 Lab 2 Properties of Water Osmosis Gloves goggles and closed toed shoes are required Bags purses backpacks must be hung on the bench hook DO NOT open the demonstration petri dishes containing potassium permanganate I will be the ONLY person to handle these dishes Dispose of Lugol s solution in the BASE waste container DO NOT fill waste containers past the indicated lines Keep containers closed when not in use No food or drink in lab Lab 2 Properties of Water Osmosis Whitney wroberson bio tamu edu Help Desk Hours M 8 9am W 9 10am or by appointment Reminders Lab Safety Forms Paper one and Howdy one Goggles If you do not have them Bring me your ID 1 Point has been deducted from your TA Points Closed Toed Shoes If you do not have them Bring me your ID 1 Point has been deducted from your TA Points Timeline Quiz 1 15 mins Lab 2 Intro 20 mins Lab Logistics Safety 5 mins Diffusion Across a Plasma Membrane and Part 2 Understanding pH 2535 mins Water is a solvent 5 mins Properties of Water 10 mins Oil and Vinegar Exp pg 24 5 mins Plasmolysis live Paramecium 20 minutes Analyze Data Clean Up 20 mins Summary 20 mins Potassium Permanganate Demo Will be announced by TA during lab take measurements every 5 mins Objectives Examine and describe the unique properties of water Use three different methods to test the pH of common household products Draw the structure of the plasma membrane and describe four ways substances enter and leave cells Differentiate between diffusion and osmosis Differentiate between passive and active transport Conduct an experiment to test the factors that affect diffusion across a selectively permeable membrane Conduct an experiment to determine water potential in plant cells Water is a Polar Molecule What is a Polar Molecule Hydrogen bonds form between positively charged H atoms and negatively charged atoms Covalent bonds share electrons within a molecule This bond is very strong Tension Cohesion Capillary Action The way plants pull water from the soil Water molecules bind to the cellulose of the plant cell wall Adhesion Surface Tension A measurement of how difficult it is to stretch or break a liquid s surface Transpiration The way plants move water from the roots to the rest of the plant Water The Universal Solvent Water is able to dissolve more and different materials than any other solvent Solute substance that is dissolved Solvent substance that does the dissolving Solution a mixture made up of a solute dissolved in a solvent Ionic Bonds bonds formed from the attraction between and charges Cation atom that loses one or more electrons Anion atom that gains one or more electrons Thermal Properties of Water Water has a high thermal capacity i e water can absorb and retain a lot of heat What areas benefit from the thermal capacity of water It takes a lot of energy to change the temperature of a body of water 1 Water retains heat once it is warmed Density Water is less dense as a solid Ice molecules are more organized and form lattices Ice floats because of the empty space in the lattice Ice has a peak density at 4 C Other Properties of Water Viscosity Water has a low viscosity which allows it to flow easily Which is more viscous Water or Honey Compatibility with Life Everything we know of on Earth requires water to survive pH Water molecules break apart into H and OH ions The log of the concentration of H equals the pH The pH of pure water is 7 What is pH The pH Scale measures acidity and basicity of a given solution More H ions more acidic More OH ions more basic The pH Scale is an inverse logarithmic scale from 0 acidic to 14 basic 7 is neutral on this scale log 10 7 7 log10 7 pH pOH 14 This can be a useful calculation to determine pH and pOH Calculations of pH H x OH 1 x 10 14 This can be used to calculate the concentration of a type of ions in a solution pH pOH 14 This can be used to calculate the pH or pOH pH Indicators Acid Base Indicators Weak acids or bases Gradually changes color over a range of pH values color change interval Anthocyanins Natural compounds that occur in plants ex Red cabbage Change color in different pH solutions Red acidic solutions Purple neutral solutions Green Yellow basic solutions pH Test Paper Paper embedded with pH indicators Good for clear and colored solutions Electronic pH Meters Very precise and accurate Plasma Membrane Plasma Membrane All cells have a plasma membrane Animal cells outer surface of cell Plant Fungi Bacteria plasma membrane lies just beneath the cell wall Comprised of phospholipid bilayer in eukaryotes and bacteria Function Support Protection Regulation of molecules entering leaving cell Where Are the Plasma Membranes Plasma Membranes Diffusion Osmosis Facilitated diffusion Active transport Transport Across the Plasma Membrane Diffusion passive transport solute molecules move from areas of high concentration to areas of low concentration Across a plasma membrane this is limited to hydrophobic molecules or small uncharged polar molecules ex water Osmosis passive transport the diffusion of water molecules Facilitated Diffusion passive transport requires the assistance of proteins to carry solute molecules down their concentration gradient across the plasma membrane hydrophilic molecules Active Transport requires energy input ATP and proteins to move solute molecules against their concentration gradients Transport Across the Plasma Membrane Diffusion These terms are relative i e they must be used in a comparison statement to make sense 3 Types of Solutions1 Hypertonic Solution of interest has a higher solute concentration compared to another solution has a lower water concentration 2 Hypotonic Solution of interest has a lower solute concentration compared to another solution has a higher water concentration 3 Isotonic Solutions have equal water and solute concentrations Diffusion Osmosis wikimedia org Osmotic Turgor Pressure Osmotic Pressure the pressure needed to stop the net movement of water Turgor Pressure pressure that pushes the cell membrane of a plant cell against the cell wall prevents wilting Pipettes Transfer Pipette Serological Pipette Pump Cell phones Cell phones are allowed to be out during this lab to use the timer and to take pictures of the experiment ONLY If I see you texting during lab time I will take your phone for the REMAINDER of the period and will deduct 3 TA points Timeline and Logistics Diffusion Passive Transport of Particles pg 27 1 hr intermittent Start 5 min 10 min