Biolab Notes - PDF

Module 1: The Microscope Microscope -​ See structures too small for the unaided eye -​ Light microscope was invented in 1590 -​ Three elements are needed to form an image: -​ - source of illumination -​ Specimen to be observed -​ System of lenses to focus illumination on specimen...

Module 1: The Microscope Microscope -​ See structures too small for the unaided eye -​ Light microscope was invented in 1590 -​ Three elements are needed to form an image: -​ - source of illumination -​ Specimen to be observed -​ System of lenses to focus illumination on specimen Compound light microscope -​ Uses natural or artificial light -​ Uses series of lenses -​ Condenser -​ Objectives -​ Magnifies and project virtual image into the body tube -​ Intermediate lenses -​ Ocular lens -​ magnifies image from objectives further and project enlarged image into eye Parts of the microscope Mechanical -​ Base: stand that supports microscope -​ Pillar: attaches to one end of base and also supports microscope -​ Handle/Arm: curved metal part from pillar for holding microscope -​ Inclination Screw: For tilting microscope and not included in current designs -​ Body tube: from handle that holds dust shield and nosepiece -​ Ocular Tube or Draw tube: holds eyepiece or ocular lens -​ Revolving Nosepiece: where objectives are attached and allows for their movement -​ Dust shield: above nose piece that protects lenses of objectives -​ Adjustment Screws: pairs of wheels attached to either side of tube -​ Coarse adjustment screw: for scanner scanner and LPO -​ Fine adjustment screw: for HPO and oil immersion -​ Stage: platform with center opening where slide is placed -​ Mirror Rack: holds mirror in place -​ Diaphragm: control amount of light -​ Condenser: below diaphragm; collects and focuses light Magnifying Parts -​ Ocular/Eyepiece: Where operator will look; usually 10x magnification; line is called pointer -​ Objectives: tube like structures on revolving nosepiece -​ Scanner: 4-5x (scanner)  -​ Low power objective (LPO); 10-12x (yellow) -​ HIgh power objective (HPO): 40-60x (blue) -​ Oil Immersion objective: 97-100x; needs cedar oil (white) -​ Total magnification of objectives -​ Scanner: 40x -​ LPO: 100x -​ HPO: 400x -​ Oil Immersion: 1000x Illuminating Parts -​ Mirror - below stage near base to collect and direct light to specimen -​ Diaphragm: control amount of light -​ Three types: iris, plate or fan -​ Condenser: below diaphragm; collects and focuses light Image of a Microscope -​ Inverted -​ Moves to the opposite direction ​ (i.e. move slide to left, image moves right; move slide towards you, image moves away) Magnification -​ Number of times image of object is enlarged by lens -​ Total Magnification = eyepiece magnification x objective magnification -​ Magnification of drawing = size of drawing/actual size of drawing Microscope care -​ Never touch lens with hand -​ Use lens paper or cotton with alcohol to clean lens Module 2: The Plant Cell Parts of plant cell -​ Cell wall -​ Coined by Robert Hooke -​ Fixed shape thats thick and rigid -​ Protects cell from external environments -​ Compared to plasma membrane -​ Flexible and delicate -​ Maintains cell’s internal environment -​ Nucleus -​ Storage and regulate DNA -​ Has nucleolus inside -​ Organelle  -​ Cannot occur in vacuole because it requires input and output from cytoplasm -​ Vacuole -​ Maintain water balance -​ Fluid filled spaces not occupied by cytoplasm -​ In young cell, often small and scattered -​ In old cell, large and fill most of cell -​ Contain substance used by plants -​ Contain ergastic substances like crystals (made of calcium oxalate or carbonate) -​ Crystals come in diff shapes -​ Prismatic (diamond) -​ Druse (star-like) -​ Rosette (star-like with many points) -​ Raphide (needle-like) -​ Cystolith (grape cluster) -​ Cell membrane -​ Provide protection from surroundings -​ Cellulose -​ Responsible for organized arrangement of cells -​ Middle camella -​ Cementing substance between cells -​ Made of calcium and magnesium pectate -​ Chloroplasts -​ Green round bodies -​ organelle -​ Functions -​ Photosynthesis -​ Carbon fixation -​ Movement is called cytoplasmic streaming/cyclosis -​ Direction is clockwise -​ Causes nucleus to be visible -​ Chromoplasts -​ orange/red oblong bodies -​ Provides plants’ color -​ Aids in pollination of seeds -​ organelle -​ Amyloplast -​ Produces starch -​ Stores starch -​ Organelle -​ Cytoplasm -​ Cell component in cell membrane -​ Does nuclear division  -​ Cytosol -​ Fluid part of cytoplasm -​ Does transportation of molecules -​ In the experiment -​ nucleus in onion cell -​ chloroplasts and cytoplasm in hydrilla -​ Chromoplast in tomato cell -​ Amyloplast in potato scrapings (stained) -​ Vacuole in tradescantia spathacea Module 3: Basic Plant cell and Tissue Types -​ Considered basic cells and tissues since they provide essential structural support, storage and metabolic functions -​ parenchyma : storage and photosynthesis -​ Collenchyma: flexible support -​ Sclerenchyma: rigid support -​ Samples of each -​ soft/bast fiber: jute, flax, hemp -​ Hard fibers: sisol, abaca -​ Not at all fibers: cotton, kopok -​ Fibers plus other cells: pineapple Parenchyma -​ Tissue -​ Composed of parenchyma cells -​ Thin-walled -​ Alive at maturity -​ Most common type of cell and tissue, constitution of all soft parts of plant body -​ Fundamental or ground tissue where other tissues are embedded -​ Special types of parenchyma cells carry out the ff: -​ Photosynthesis -​ Storage -​ Respiration -​ Division -​ Protection -​ Secretion -​ Excretion -​ Protective epidermis is composed of parenchyma cells -​ These cells can resume meristematic activity -​ Play important role in wound healing, regeneration, formation of adventitious roots and shoots, and vegetative reproduction -​ Most only have primary non lignified cell walls -​ Some develop secondary walls and become lignified  -​ Chlorenchyma -​ Contain chloroplasts -​ Hydrilla -​ dieffenbachia -​ Storage parenchyma -​ Contain amyloplasts -​ Potato -​ Canna indica petiole -​ Aerenchyma -​ Has large air spaces -​ Stellate parenchyma -​ Highly branched with adjacent cells connected to each other by branches Collenchyma -​ Living tissue -​ Elongated cells with unevenly thickened and non lignified primary walls -​ Simple tissue composed of only collenchyma cell -​ Similar to parenchyma cells -​ Complete protoplasts capable of meristematic activity -​ Capable of photosynthesis -​ Unevenly thickened, thicker walls of collenchyma cells -​ Occurs at corners where cells meet -​ Begin early in shoot development -​ Increases simultaneously as organ elongates -​ Because wall thickening are plastic, unable to regain original length when stretched -​ Capable of extension -​ Do not hinder elongation of stem and leaf -​ Found in groups along sides of young stems and in stalk and midrib leaves -​ Provide support -​ Samples -​ Plectranthus -​ Dieffenbachia -​ Canna indica Sclerenchyma -​ Tissue -​ Evenly thickened secondary walls, often lignified -​ Do not retain protoplasts at maturity -​ Looks empty -​ Cells walls of these cells absorb stains, which are visible in prepared slides -​ Fibers -​ Long spindle-shaped cells  -​ Support both primary and secondary tissues -​ Occur in strands in cortex, phloem, xylem and in sheaths or bundle-caps associated with vascular bundles -​ Phloem fibers of eudicots -​ Bast fibers -​ Soft fibers -​ Soft and flexible -​ Monocot leaf fibers -​ Hard fibers -​ Strongly lignified -​ Hard and stiff -​ Luffa (patola) scrub -​ Sclereids -​ Support both primary and secondary tissues -​ Short cells -​ Thick secondary walls -​ Strongly lignified -​ Provided with numerous simple pits -​ Sclereid-like fibers are widely distributed in plant body -​ Occur in stems, leaves, fruits and seeds -​ Brachysclereids -​ Stone cells -​ Found in cortex, phloem and pith of stems and in fruit flesh -​ pear -​ Macrosclereids -​ Elongated and columnar -​ Found in leguminous seed coats -​ Osteosclereids -​ Bone cells -​ Columnar with enlarged ends -​ Astrosclereids -​ Star cells -​ Lobes or arms diverging form central body -​ Found in leaves of eudicots Module 4: Material Transport in Cells -​ Cell membranes need to maintain equilibrium -​ Maintained by regulation of transport of substance in and out of cells -​ Diffusion -​ Simplest method -​ Molecules in solution move from region of higher concentration to lower concentration -​ Osmosis  -​ Diffusion through membrane -​ Tonicity -​ Dictated by solute concentration and membrane permeability -​ Ability of solution to cause cell to gain or lose water -​ Turgid -​ Healthy state for most plant cells -​ Flaccid -​ When there is no net tendency for water to center cells -​ Plasmolysis -​ Osmotically induced shrinkage of cytoplasm -​ Causes plant to wilt and can be lethal -​ Plants in -​ Hypotonic solution (less solute relative to cell) -​ Plants will swill as water enters by osmosis -​ Isotonic (same solute concentration) -​ No tendency for water to go in -​ Hypertonic (higher solute concentration) -​ Lose water to surrounding and shrink -​ Imbibition -​ Transport mechanism not requiring semi-permeable membrane -​ Involves uptake of water by substances that do not dissolve water -​ Results in swelling of substance -​ Property of biological substances -​ Cellulose, starch and some proteins -​ Occurs in dry seeds before they germinate -​ Totally unrelated to osmosis A.​ Effect of heat on diffusion of selected plant pigments using atsuete -​ From light to dark -​ Vegetable oil -​ Distilled water -​ Heated distilled water -​ Heated vegetable oil -​ Caused by diffusion of its water soluble pigments which is affected by the pigments solubility, concentration and temperature -​ Cell membranes pigments need to diffuse the ff to reach outside of cell -​ Chromoplast -​ Cell membrane -​ Cell wall B.​ Osmosis: Cell changes in Plasmolysis -​ Vacuole shrinks C.​ Imbibition -​ Woods and seeds imbibant water best  -​ Rubber imbibant kerosene best -​ Living and dead cells can partake in it as it doesnt require semi permeable membrane -​ Process allows seeds to absorb water and soften Module 5: Photosynthesis -​ Process whereby green plants convert radiant energy of light into chemical energy that is then stored in food molecules -​ Light, green pigment and carbon dioxide must be present -​ Process takes place in chloroplasts -​ Basic equation -​ 6CO2 + 12H2O -> C6H12O6 + 6H2O + GO2 -​ Reactants: Carbon dioxide and water -​ Products: Glucose, water, oxygen -​ Main produce is glucose and follows three pathways -​ Converted into other chemical substance required by plants​ (cellulose in cell walls) -​ Converted into starch, storage molecule that can be broken down to glucose again -​ Broken down during cellular respiration to release energy needed by plants for growth and development A.​ Light as requirement for photosynthesis -​ Photosynthesis create glucose or starch that reacts with iodine and causes a dark blue color -​ In experiment, plant with light has darker color than plant that was covered B.​ Carbon dioxide as requirement for photosynthesis -​ For A: no plant to process carbon dioxide therefore no photosynthesis -​ For C: no carbon dioxide for plant to use in photosynthesis -​ For B -​ Carbon dioxide is used in photosynthesis which causes the color change -​ Glucose produced by photosynthesis is used in plant respiration which causes the color to go back C.​ Separation of chloroplasts pigments by paper chromatography -​ Chromatography -​ Helps identify different pigments in plants -​ Show how plants adapt to light by analyzing pigment composition -​ Method of separating closely related compounds -​ Allows mixture of substances to diffuse through absorbent called chromatogram -​ Chloroplast pigments can be separated and observed as different color bands on chromatogram -​ Band and pigment -​ Yellow: carotene  -​ Absorbs light and prevents chlorophyll from damage -​ Yellow-grey: phaeophytin -​ Transfer electron in photosystem -​ Yellow-brown: xanthophyll -​ More soluble in solvent -​ Less attraction to chromatography paper -​ Protective role -​ Absorb excess light -​ Prevent photooxidative damage -​ Bright green to blue green: chlorophyll a -​ Main pigment -​ Absorbs light energy efficiently -​ Yellow green to olive green: chlorophyll b -​ Less soluble -​ More attracted to chromatography paper -​ Accessory pigment to broaden spectrum of light absorption -​ Chlorophyll can be identified by band color and distance travelled -​ Retention factor (rf) is ratio that can be compared to standards to identify unknown compounds -​ Rf = distance of pigment from origin/distance of solvent from origin