Lab 1 notes osmosis smartboard
- 1. Lab 1 Notes Osmosis & Diffusion Atoms/ molecules • Make up cells • Have kinetic energy • Are constantly in motion • Bump into each other & change direction • Results in diffusion (random movement of molecules from area of higher concentration to lower concentration) e.g. opening bottle of perfume in a room Diffusion • Vital to many life functions in a cell • Allows for nutrient transport without expenditure of excess energy • Allows O2 and CO2 exchange in the lungs and between body’s intercellular fluid and the cells • Aids in transport of nutrients and H2O in xylem of plants • Allows for absorption of H2O into roots Dynamic Equilibrium • Atoms & molecules evenly distributed • Concentrations equal
- 2. • Movement doesn’t stop • No net movement from one area to another Selectively permeable membrane • Only allows movement of certain solutes (O2, CO2, C6H12O6) and water (H2O) • Plasma membranes • Dialysis tubing Osmosis • Type of diffusion • Movement of H2O through semi permeable membrane • H2O moves from area of high water potential (hypotonic solute concentration) to a region of lower water potential (hypertonic solute concentration) Solute+ • Substance being dissolved • May be solids, liquids, or gases Solvent • Dissolving substance • H2O universal solvent
- 3. • H2O most common solvent in living things Types of solutions 1.Isotonic • Equal concentrations of solute in both solutions • Dynamic equilibrium reached • Net movement between solutions equals zero 3% NaCl 97% H2O 3% NaCl 97% H2O 2.Hypertonic • Solution with higher concentration of solute than a compared solution • H2O diffuses into the cell • Cytolysis (bursting occurs in animal cells due to too much water flowing into the cell • Saltwater fish & other animals in hypertonic solutions must find ways to retain water • Produces turgor pressure inside of plant cells as water contains to move inward putting pressure against the plant cell wall 1% NaCl 99% H2O 3% NaCl 97% H2O
- 4. 3.Hypotonic solutions • Solution with a lower solute concentration than a compared solution • H2O diffuses out of the hypotonic solution • Cells shrink or crenate as they loose H2O; called plasmolysis • Animal cells lose shape & shrivel up • In plant cells, turgor pressure decreases pulling plasma membrane away from cell wall; plants wilt • Paramecia in freshwater ponds must develop mechanisms to pump out excess water 3% NaCl 97% H2O 1% NaCl 99% H2O Water Potential Ψ • Used by botanists to determine movement of H2O into & out of plant cells • Represented by Greek letter psi (Ψ)
- 5. • Includes 2 components --- pressure & solute potential • Ψ = Ψp + Ψs • H2O moves from area of higher water potential (higher free energy & more H2O molecules) to an area of lower water potential (lower free energy & fewer H2O molecules) • H2O diffuses down a water potential gradient • Water potential of pure H2O at atmospheric pressure is zero (Ψ = O) • Water potential values can be zero, positive, or negative Two factors affecting water potential 1. Addition of solute • Lowers water potential • Inversely proportional to water potential • Always a negative value since pure water is zero 2. Pressure potential • Increasing pressure increase water potential • Directly proportional to water potential • Usually positive in living cells
- 6. • Increasing Ψ p causes a positive value; pressing on bulb of eyedropper causes water to be dispensed • Decreasing Ψ p results in a negative value; cells pull or suck in water Determining Solute Potential • Ψ s = -iCRT • i – ionization constant (equals 1 for sucrose because sucrose doesn’t ionize in water) • C = molar concentration • R = pressure constant (R = 0.0831 liter bars/ mole oK • T = temperature oK (273o + oC of solution) • Example: l.0 M sucrose solution at 22oC under standard atmospheric conditions ψ s = -I x C x R x T ψ s = -1 (1)(.0831)(273+22) ψ s = -1(1)(.0831)(295) ψ s = -24.51 bars • ψ = ψ p + ψ s therefore, ψ = o + (-24.51)