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Unformatted text preview: BIOL 112 – Lab Review Lab 1: The Microscope and Experimental Design • Hypothesis : A tentative explanation for a well-framed question • Four objective lenses: o Scanning objective (3.2x) o Low power objective (10x) o High power objective (40x) o Oil immersion objective (100x) • Total magnification = magnification of eyepiece x magnification of objective x magnification of binocular tube (1x) • Coarse focus = only on scanning and lower power objectives • Selective staining: o Safranin red = lignified cell walls o Fast green = cellulose cell walls o Crystal violet = starch grains • Controls: o Negative : Something you know for a fact does not cause the desired effect, ensures no false positive If the response of your unknowns looks like the response in the negative control, you know that the unknown is not having the effect you are looking for. o Positive : Something you know for a fact causes the response you want Confirms the variable produces the effect you are looking for. Lab 2: Microbiology I – Bacteria • Summary: Plating Serratia marcescens and counting colonies at incubation intervals of 30 mins. • Pathogens: Bacteria that cause Disease • Morphology o Cocci = spherical o Bacilli = rods, cylindrical o Spirilla = helical • Most bacteria divide by fission • Doubling / Generation Time: The time required for one cell to divide into two • Describing colonies: o Round or irregular shape o Convex or flat o Pigmented or non-pigmented o Indication of consistency – buttery, hard, mucoid • Binomial nomenclature: Capitalized genus, followed by lower case species • Gram positive (purple/blue) = thick peptidoglycan wall, retains dye • Gram negative (red/pink) = thin peptidoglycan wall, does not retain dye • # of generations of bacteria: 2^n = b/B o n = # of cell generations o b = # of cells at t, ex. t = 120 min o B = # of cells at t = 0 Lab 3: Cell Membrane Transport • Summary: o Placing pieces of beet in different concentrations and types of alcohols to observe the permeability of alcohols. More pigment released = more penetration. o Slices of turnip put into KCl at different temperatures – 2˚C and 25˚C, and a water (control). Higher temperature = more transport (faster rate of diffusion/osmosis) • Brownian movement: Dye particles in water - each particle is constantly being bumped by moving water by molecules which collide with the dye particles setting them in random motion. Other examples = pollen grains in water. • Diffusion: Movement of molecules from high concentration to low concentration. Dynamic equilibrium is eventually established. • Osmosis: Diffusion of solvent across a semi-permeable membrane • Hypotonic solution : [inside cell] > [outside cell], solvent rushes in cell, causes it to swell and possibly burst • Hypertonic solution: [outside cell] > [inside cell], solvent leaves cell, causing it to shrink • Isotonic solution: [inside cell] = [outside cell], no net movement • When beet cells are damaged by alcohol, the red pigment betacyanin is released.When beet cells are damaged by alcohol, the red pigment betacyanin is released....
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This note was uploaded on 02/15/2012 for the course BIOL 112 taught by Professor Lasko during the Winter '08 term at McGill.
- Winter '08