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  • Biology lab 111

  • Experiment 3: the microscope: - The unaided eye has a resolving power of about 0.1mm - Light microscope has a resolving power of about 2 - Light microscope can improve resolution as much as 1000 times, compared to the unaided eye - Contrast means increasing differences between the lightest and the darkest parts of an image - The microscope is carried by holding the arm with one hand and supporting the base with the other


    Light microscope systems: 1- Mechanical 2- Illuminating 3- Imaging

    Mechanical parts: 1- Tube 2- Arm 3- Nosepiece 4- Base 5- Stage 6- Focusing knob

    Imaging parts: 1- 3-4 objective lenses 2- 1-2 ocular lenses

    Illuminating parts: 1- Light source 2- Condenser lens 3- Iris diaphragm - Focusing knobs are coarse adjustment knob and fine adjustment knob - If air bubbles present in wet mount preparation, such bubbles appear as circles of various sizes with

    dark edges - Always start your microscopic study with the 4X objective lens - Never use coarse adjustment knob when you view a specimen with the 40X objective lens

    Total magnification = objective lens magnification * ocular lens magnification

    - The image of the specimen in the light microscope is inverted

    Types of microscopes:

    1- Light microscope 2- Dissecting microscope 3- Phase contrast microscope 4- Transmission electron microscope 5- Scanning electron microscope

    Dissecting microscope: - Has two oculars and two tubes

  • Disadvantages: 1. Limited magnification and resolution

    Advantages: 1- 3D image 2- Larger working distance 3- Viewing large objects

    Phase contrast microscope: - Studying alive specimen without killing them

    Transmission electron microscope: - Electron beams are used as a source of illumination instead of light waves - Operated under vacuum - Has electromagnetic lenses - Magnification can reach 1,000,000 - Resolution may reach 0.2nm - Specimen has to be cut into sections as thin as 60-100nm and must be stained with heavy metals to

    make them electron dense

    Scanning electron microscope: - The surface of the specimen must be coated with a thin layer of gold - The energy in the electron beam makes the gold emits more electrons which are picked up by a

    detector - Results in a picture of the surface of the specimen on a cathode ray tube

    Experiment 4: the cell: - All cells have a plasma membrane, a region of DNA or nucleus, and a cytoplasm

    Types of cells: 1- Prokaryotic 2- Eukaryotic - Prokaryotic cells are bacteria, compose the domains eubacteria and archeabacteria

    Eukarya kingdoms:

    1- Animals 2- Plants 3- Protists 4- Fungi - Eubacteria include bacteria and cyanobacteria

    Bacteria shape: 1- Bacilli 2- Spirilli 3- Cocci

    Bacteria in yoghurt: - Yoghurt contain lactobacillus

  • - Lactobacillus adapted to live on lactose and converts milk to yoghurt - Methelyne blue pigment used

    Cyanobacteria: - Photosynthesis prokaryotes - Exist as colonies and filaments and as a single cells - A slide of anabaena which is a filamentous cyanobacteria is used to observe cyanobacteria

    Eukaryotic cells kingdoms: 1- Protists 2- Animalia 3- Plantae 4- Fungi - Nucleus and mitochondria and chloroplast are membrane bound structure

    Human cheek cells: - Protection function - Methylene blue is used

    Human skin cells: - Methylene blue is used

    Onion epidermal cells: - The onion is made up of thickened modified leaves called scales - The onion epidermal cells comes from a thin translucent tissue which lines the scales outer curve - Lugol's stain is used

    Experiment 5: biological macromolecules: Classes of macromolecules:

    1- Carbohydrate 2- Lipids 3- Proteins 4- Nucleic acids - The chemical properties of classes depend on functional groups - Dehydration is joining building blocks - Hydrolysis are breaking down of polymers

    Carbohydrates: - Glucose is a 6 carbon aldose - Fructose is a 6 carbon fructose - Two glucose molecules form maltose - Glucose and fructose form sucrose - Glucose and galactose form lactose

    Polysaccharides examples: 1- Starch 2- Glycogen 3- Cellulose 4- Chitin

  • Benedict's test: - To detect reducing sugars - Reducing sugars have free aldehyde or ketone groups - Benedict reagent consist of CuSO4 making it blue colored - The positive sign is orange-brownish color - This test needs boiling

    Lugol's test: - To detect starch - Yellowish-brown color is a negative sign - Bluish-black color is a positive sign - Iodine only interact with coiled molecules - Doesn't need boiling

    Proteins: - The building block of proteins are amino acids - Amino acid are linked together by a peptide bonds

    Proteins types: 1- Structural 2- Regulatory 3- Storage 4- Contractile 5- Transport

    Ninhydren test: - To detect amino acids - Ninhydren reagent reacts with free amino groups - A purple or violet color is the positive sign - Need boiling

    The biuret test: - To detect peptide bonds - A violet color is the positive sign - Doesn't need boiling

    Lipids: Lipid classes:

    1- Neutral fats 2- Phospholipids 3- Steroids

    - Cholesterol is an example of steroids

    Sudan red test:

    - To detect lipids - A red color is a positive sign - Doesn't need boiling - The final step is mixing with vortex

  • Lipid solubility test:

    - Lipids are soluble in nonpolar solvents such as alcohols - To detect the solubility of lipids - The final step is mixing

    The grease spot test:

    - The spread of oil on a paper sheet to give a transparent spot Nucleic acids: Types of nucleic acids:

    1- DNA 2- RNA

    Types of nitrogenous bases: 1- Purines 2- Pyrimidines

    Purine types: 1- Adenine 2- Thymine 3- Cytosine 4- Guanine

    - Uracile is found only in RNA instead of Thymine - Pyrimidine have only one ring while purine have two

    Extraction of DNA:

    - The final step is to invert the tube several times

    The Dische diphenylamine test:

    - To detect DNA - A blue color is a positive sign - Need boiling

    Experiment 6: enzymes:

    - Most enzymes are proteins

    Enzyme categories: 1- Hydrolytic 2- Oxidizing 3- Reducing

    - Enzymes are categorized depending on the type of reactions they control - Rennin coagulate milk protein which is casein - Catechol oxidase react with catechol to give a dark brown color

  • Factors affecting enzyme activity:

    - Rennin alters the 3D structure of casein - Rennin allows the digestion of milk to be more effective by slowing its passage through the

    digestion system

    Factors affecting enzyme activity:

    1- Temperature 2- Ph 3- Enzyme concentration


    - High temperatures denaturate the active site of the enzyme - Low temperature stops the enzyme activity - Enzyme can survive low temperatures but not the high temperatures


    - Enzyme can't work in acidic or basic solutions

    Catechol oxidase test:

    - To detect catechol oxidase - By adding catechol to the reaction mixture - Dark brown color is the positive sign - Catechol oxidase forms benziquinone - Catechol is poisonous - Phenylthiourea is an inhibitor of catechol oxidase - Phenylthiourea must be added to solution before the enzyme to inhibit its activity before

    completing its job

    Experiment 7: physical properties of the cell:

    - Brownian movement has been discovered by Robert brown - Diffusion is the movement of molecules from higher concentrations to lower concentrations - An example of diffusion within liquids is the addition of liquid dye to water

    Observing Brownian movement:

    - We use carmine dye to observe it

    Effect of temperature on Brownian movement:

    - Temperature and Brownian movement are proportionally related - As the temperature increases the Brownian movement increases

    Diffusion within solution:

    - Starch and iodine = color change inside the bag only - Iodine move inside the bag where the starch located

  • - Phenolphthalein and sodium hydroxide = color changes in and outside

    Diffusion within semisolid medium:

    - The less the molecular weight the bigger the diameter


    - Osmosis is the diffusion of water across a selectively permeable membrane - Hypotonic means greater concentration in the cell - Isotonic means equal concentrations - Hypertonic means less concentration in the cell

    Osmosis in plant cell:

    - We use elodea or onion epidermal cells to observe the osmosis in the plant cells

    Osmotic pressure:

    - We will use osmometer - Osmometer is filled with molasses or sugar solution - The height of the solute in the tube increases as the concentration of sugar increases

    Experiment 8: metabolism: Examples of photosynthetic autotrophs:

    1- Green plants 2- Some monera 3- Some protists

    Examples of heterotrophs: 1- Most monera 2- Some protists 3- All fungi 4- All animals

    - Anabolism is synthesis reaction - Catabolism is breaking down reaction

    Respiration: Alcoholic fermentation:

    - Carried out by yeast in an anaerobic process - Oxygen-stressed muscles of animals carry out lactic acid fermentation

    Measuring yeast fermentation:

    - Baker's yeast, sacharomyces cerevisiae is used - Starch is converted to glucose - Respirometer is a set to see fermentation

  • Cellular respiration:

    - Respiration is a catabolic reaction



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