Lab 1: Microscopy and Biological Illustrations

• Parts of the Microscope

  • OCULAR = the lens you look through, also known as an eyepiece at the top of the microscope (10X)

  • OBJECTIVE LENS = the lenses that scan the specimen located on the revolving nose piece

    • four of them - 4X, 10X, 40X and 100X

      • 4X = scanning objective

      • 10X = medium power

      • 40X = high power

      • 100X = oil immersion

  • REVOLVING NOSE PIECE = the disc shaped housing for the objective lenses

  • STAGE = the large platform below the revolving nosepiece which contains the objectives

  • STAGE CLIPS = hold the specimen slide in place

  • BASE = supports the microscope and contacts the table

  • ARM = the ‘handle’

  • LIGHT SOURCE = the light used to illuminate the specimen, typically adjustable

  • CONDENSER = a third set of lenses located under the stage that collects the light rays from the light source and focuses into a single point on the specimen - does NOT magnify the specimen - instead changes the resolution of the specimen

  • COURSE ADJUSTMENT KNOB = the larger knob used for initial lens focussing at low power, larger movements

  • FINE ADJUSTMENT KNOB = the smaller knob on top of the course knob used for precise focussing under higher power

  • IRIS DIAPHRAGM = the means of adjusting the amount of light striking the object

• Types of Microscopes

  • PARFOCAL = an image in focus at one magnification will be almost is focus as you increase magnification

  • PARCENTRAL = an object in the centre of the field of view at 4X or 10X will still be centred when swapping up to 40X

• Calculations

  • Total Magnification - multiplying the eyepiece magnification by the objective magnification

    • 10X ocular x 4X objective = 40X total mag.

  • Field of View/Magnification

    • field of view #1 x magnification #1 = field of view #2 x magnification #2

  • Average Object Size

    • size of field of view/ # of objects across the field

  • Conversions

    • 1m = 1,000mm

    • 1mm = 1,000um (micrometers)

    • 1mm = 1,000,000nm

    • 1um = 1,000nm (nanometres)

• RESOLUTION FACTORS:

  • wavelength of light (inverse relationship)

  • refractive index

    • medium, the light shines through (oil, air, water)

  • numerical aperture (proportional relationship)

    • calculated from certain physical properties of lens the angles at which light enters and leaves the lens

• CONTRAST = based on the differential absorption of light by the different components of the specimen - can be improved by adding stains

• Important to Illustrations

  • FIELD OF VIEW = everything that can be seen in the circle of light that is projected when looking through the ocular

  • WORKING DISTANCE = distance between the tip of the objective and the surface of the specimen

  • DEPTH OF FIELD = refers to the thickness of the specimen of focus (constant value for each objective)

  • SCALE = diameter of field of view/ # of objects that can fit

• Biological Illustrations How To:

  • always in pencil

    1. a circle to indicate field of view

    2. descriptive title centred beneath the drawing

       • specimen depicted (fixed or living)

       • whole mount (w.m.), cross section (x.s.), longitudinal section (l.s.)

    3. indicate minimally:

       • name of slide (genus species?)

       • kingdom

       • total magnification

       • labelled structures (what are they list)

    4. draw to scale and include size scale

       • measure directly the object size or work backwards and estimate

    5. label structures and connect with ruled straight line

    6. make sure it is recognizable to you or others

    7. finalize drawing

    8. add:

       • student name

       • laboratory section

       • instructor’s name date

• Experimental Components

  • SAMPLE = unidentified solution or experimental mixture

  • NEGATIVE CONTROL = substance that does not react in the test

    • a known negative (compared to sample)

  • POSITIVE CONTROL = substance that does react in the test

    • known positive (compared to sample)

Lab 2: Biological Macromolecules and Food Analysis

• Reagents:

  • Benedict’s Reagent

    • tests for reducing sugars based on their ability to reduce weak oxidizing agents

      • Inorganic = blue

      • very high monosaccharide/disaccharide concentration = reddish orange

      • high monosaccharide/disaccharide concentration = orange

      • moderate monosaccharide/disaccharide concentration = yellow orange

      • low monosaccharide/disaccharide concentration = yellow

      • very low monosaccharide/disaccharide concentration = green

      • Polysaccharide = blue (no change)

  • Lugol’s Reagent

    • tests for the presence of starch using iodine/potassium

      • starch present = blue

      • no starch = amber (no change)

  • Sudan IV

    • used to identify the presence of lipids in liquids

      • lipids = red

      • no lipids = clear/translucent

  • Biuret’s Reagent

    • copper based solution will react with peptide bonds producing a colour change (will not react to free amino acids)

      • no protein or peptides = blue

      • proteins = purple

      • peptides = pink

  • Ninhydrin Reagent

    • detects free amino acids and proline (ring structure amino group) with a colour change

      • free amino group/acid = purple or violet

      • proline/ non-free amino groups = yellow

  • 3,2,5-Triphenyl Tetrazolium Chloride

    • oxidized tretrazolium is colourless and turns pink when reduced

      • active ETC = pink or red

      • non-active ETC = colourless

Lab 3: A Closer Look at Cells

• Four Features of ALL Cells

  • plasma membrane

  • ribosomes

  • DNA

  • cytoplasm

• Why Stain?

  • typically use methylene blue

    • the dye accumulates in the nucleus/chromatin

Lab 4: Diffusion and Osmosis

• Active vs Passive Transport

  • Active Transport = when energy is required to drive the transfer of a substance across the membrane against the concentration gradient

  • Passive Transport = does not require the input of energy and flows with the concentration gradient (diffusion)

• Types of Diffusion:

  • Simple Diffusion - when small non-polar molecules can easily slip through the lipid bilayer

  • Facilitated Diffusion - when substances need the help of protein gates to diffuse across the membrane

  • Osmosis - diffusion of water molecules across a selectively permeable membrane or plasma membrane

    • low solute concentration (high water) to high solute concentration (low water)

    • spontaneous process

      • OSMOLARITY = the measure of solute concentration in a solution

• Water Pressure in Plants

  • Turgor Pressure = the pressure of the cytoplasm against the cell wall

    • these cells are said to be Turgid or have Turgidity

  • Plasmolysis = cytoplasm/cell membrane shrinks away from the cell wall as water is lost to the hypertonic environment

    • Cyclosis = streaming of the cytoplasm

• Water in Red Blood Cells

  • Lysed = the destruction of a cell by the influx of water

    • if it is a red blood cell specifically - haemolysis

  • Crenate/shrivelled = water moves out of the cell

Lab 7: Cell Respiration and Photosynthesis

• AEROBIC = oxygen-requiring process

• ANAEROBIC = a non-oxygen-requiring process