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• Magnifying parts


  1. To enlarge the object

  2. Objective lens and ocular lens
• Eyepiece


  • Final image is viewed
  • To enlarge the specimen
  • Magnification: 10x or 15x
• Objective Lens


  • Enlarge the object depending on the objective lens used
  • Objective lenses are connected to the revolving nosepiece
  • Magnification – degree of enlargement of an object provided by the microscope; how it can enlarge the specimen
  • Magnification and its Color: Scanner (Red): 4x, Low Power (Yellow): 10x, High Power (Blue): 40x, Oil Immersion (White): up to 100x, Cedarwood oil – most common oil for oil immersion objective
  • Total Magnification = eyepiece x objectives
• Illuminating parts


  1. Gives light to the sample from the light source to the stage

  2. Substage condenser, iris diaphragm, and light source
• Condenser


  • Controlling the intensity of the light passing to the image
  • It increases or decreases the angle of the light
  • Image became brighter or darker
  • Depth of field will be reduced when the iris diaphragm of the condenser is opened
• Diaphragm


  • Controls the light reaching the object
  • Changes the width of the light (wider or thinner)
  • Close the condenser to see the image more clearly
• Light Source


  • Controlling the intensity or brightness of the light
  • Usually found on the base of the microscope (on/off switch)
  • Lamp rheostat – controls the brightness
  • Tungsten-halogen lamps – most highly reliable light sources for light microscopy
  • 2 Types of Knobs: Course Adjustment Knob (Objective lenses can be moved towards or away from the specimen, For scanner and LPO), Fine Adjustment Knob (For fine tuning, For high objective lenses)
• Mechanical parts

  1. Hardware or support

  2. Base, c-shaped arm, and stage
• Base


  • It helps in holding the various parts of microscope
  • Contains the light source
• Arm


  • Used for holding the microscope
  • Connects the base to the objectives and eyepiece
  • Hold the microscope using one hand under the base, and the other arm holding the arm of the microscope
• Mechanical Stage


  • A rigid platform on which specimen is placed to be viewed
  • Aperture – permits the light from the light source to the object of preference
  • X-Y Translational Control Knobs – moves the stage
• Carrying the Microscope – Hold the C-shaped arm with one hand and other hand under the base.
• Cover the Microscope – Never allow direct light to fall on the microscope.
• Focusing the OIO – While using oil immersion objective, do not adjust the coarse screw.
• OIO Aftercare – Oil immersion objective should be cleaned after use by wiping with soft cotton cloth or lens paper.
• Objectives – Dry objective should never come in contact with oil.
• Cleanliness – At the end of every experiment, clean the lenses with lens paper.
• Default Position – The scanning objective or the LPO should be the one in focus and the stage should be centered and lowered
• Storage – When the microscope is returned in the cabinet, the microscope's arm must face the opening of the cabin.
• Nucleus


  • Contains most of the genes in a eukaryotic cell (some genes are located in the mitochondria)
  • About 5 microns in diameter
  • In the nucleus, the DNA and the a
• Storage


  When the microscope is returned in the cabinet, the microscope's arm must face the opening of the cabin
• NUCLEUS


  • Contains most of the genes in a eukaryotic cell
  • About 5 microns in diameter
  • In the nucleus, the DNA and the associated proteins are organized into fibrous material called chromatin
  • Carries genetic material
  • When the cell prepares to divide, the chromatin fibers coiled up and become chromosomes
• NUCLEOLUS


  • A region (in the nucleus) of densely stained fibers and granules adjoining chromatin
  • rRNA – ribosomal RNA (synthesize protein)
• RIBOSOMES


  • Its function is to synthesize protein
  • Prokaryotes = 70 subunits; eukaryotes = 80 subunits
  • Bound and free ribosomes are structurally identical and can alternate between the two roles
  • Bound – attached in the ER or nuclear envelope
  • Free – freely roaming in the cytosol
• ENDOPLASMIC RETICULUM


  • Consist of a network of membranous tubules and sacs called cisternae
  • 2 Types: Smooth Endoplasmic Reticulum (Without ribosomes, Synthesis of lipid, glycogen metabolism, store calcium) and Rough Endoplasmic Reticulum (With ribosomes, Synthesis of secretory proteins, cell membrane protein, and organelle protein)
• GOLGI APPARATUS


  • Major sites for carbohydrate synthesis
  • Sorting and dispatching station for the products of the ER
  • Consists of flattened membranous sacs
  • A Golgi stacks has polarity: cis face (receiving site of Golgi apparatus; situated near the ER) and trans face (shipping site of the Golgi apparatus)
  • Golgi Apparatus cisternae (not interconnected); endoplasmic reticulum cisternae (interconnected)
• LYSOSOMES


  • Contain hydrolytic enzymes (required acidic pH) to digest
  • Proteins, polysaccharides, fats, and nucleic acids
  • Autophagy – self-eating or self-digesting
  • Reasons: digest the nutritious materials that are safe for the cell, wants to kill something (bacteria and virus), can recycle its own organic material
• MITOCHONDRIA


  • The powerhouse of the cell
  • Energy transformer of cells
  • Principal site of intracellular digestion
  • Cristae – pockets of fluid reservoir
• CYTOSKELETON


  • Backbone of the cell
  • A network of fibers extending throughout the cytoplasm
  • Functions: Provide mechanical strength to the cell, Establish cell shape, Locomotion, Intracellular transport of organelles
• 3 Types of Fibers in Cytoskeleton

  • Microtubules (determines the positions of membrane-enclosed organelles, intracellular transport), Microfilament (determines the shape of the cell and is necessary for whole cell locomotion or movement), Intermediate Filament (provides mechanical strength and resistance to shear stress)
• CENTROSOMES AND CENTRIOLES


  • Centrosomes (a region near the nucleus from which microtubules sprout, microtubule organizing center, contains a pair of centrioles), Centrioles (Composed of 9 sets of triplet microtubules arranged in a ring, Centrioles replicate before cell division)
• Centrosomes


  1. Region near the nucleus from which microtubules sprout

  2. Microtubule organizing center

  3. Contains pair of centrioles
• Centrioles


  1. Composed of 9 sets of triplet microtubules arranged in a ring

  2. Replicate before cell division

  3. Help in microtubule assembly
• Cilia and Flagella


  1. Provide locomotion for the cell or move fluid past the cell

  2. Cilia sweep mucus

  3. Flagella has an undulating motion that generates force in the same direction as the flagellum’s axis
• Only cilia and flagella can be routinely distinguished by light microscope
• Interphase


  1. The longest period consisting of G1, S-phase, and G2

  2. G1 period is when cells accumulate enzymes and nucleotides needed for DNA replication

  3. S-phase is devoted primarily to DNA replication

  4. G2 is a short period of preparation for mitosis
• Prophase


  1. Nucleolus disappears and replicated chromatin condenses into discrete chromosomes

  2. Centrosomes with duplicated centrioles separate and migrate to opposite poles of the cell

  3. Lamina and inner nuclear membrane disassemble and disperse

  4. Spindle fibers start to migrate

  5. 2 chromatin forms 1 chromosome
• Metaphase


  Chromosomes condense further and align at the equatorial plate
• Anaphase


  Sister chromatids separate and move toward opposite spindle poles
• Telophase


  1. Chromosomes revert to uncondensed state

  2. Microtubules depolymerize, nuclear envelope reassembles

  3. Belt-like contractile ring of actin filaments develops at the cell's equator

  4. Cleavage furrow forms during cytokinesis, dividing the cytoplasm into two daughter cells