MICROSCOPY AND CELL

• Magnifying Parts

  1. Ocular/Eyepiece

  2. Objective Lenses
• Total magnification = magnification of objective lens x magnification of ocular lens
• Types of Microscopes

  • Simple Microscope - uses a single lens to magnify the object
  • Compound Microscope - uses several lenses to magnify the object
• Nucleus


  1. Structure: Large structure enclosed within a double membrane; contains chromatin, nucleolus, and nucleoplasm

  2. Major Function: Houses the DNA that serves as the genetic material for directing protein synthesis
• Nuclear Envelope


  1. Structure: Double membrane boundary between cytoplasm and nuclear contents; continuous with rough endoplasmic reticulum

  2. Major Function: Separates nucleus from cytoplasm
• Microscope


  Instrument used for viewing small objects, including microbes, can magnify a specimen and optically resolve fine detail
• Parts of a Compound Microscope

  1. Magnifying Parts

  2. Illuminating Parts

  3. Mechanical Parts
• Magnifying Parts

  • Scanning Objective - 4x [red]
  • LPO - 10x [yellow]
  • HPO - 40x [blue]
  • OIO - 100x [black]
• Types of Electron Microscopy

  • Transmission Electron Microscopy (TEM)
  • Scanning Electron Microscopy (SEM)
• Cell


  smallest unit parts of the body
• Nucleolus


  1. Structure: Large, prominent structure within the nucleus

  2. Major Function: For synthesis of ribosomes
• Endoplasmic Reticulum

  • Consists of a network of membranous tubules and sacs called cisternae [foldings]
• Cytosol

  • Provides support for organelles; serves as the viscous fluid medium through which diffusion occurs
• SMOOTH ER

  • Does not have ribosomes
  • Synthesis of lipid
  • Glycogen metabolism in the liver cells
  • Store calcium
• MITOCHONDRIA


  • Structure: Double membrane-bound organelles containing a circular strand of DNA (genes for producing mitochondrial proteins)
  • Major Function: Energy transformers of cells, Synthesize most ATP during aerobic cellular respiration by digestion of fuel molecules [glucose] in the presence of oxygen, Cristae
• GOLGI APPARATUS

  • Major sites for carbohydrate synthesis
  • Sorting and dispatching station for the products of the ER
  • Consists of flattened membranous sacs (CISTERNAE)
  • Golgi stacks has polarity: cis face [receiving site of the golgi apparatus; located near the ER; cis, pa-receive] and trans face [shipping site; located away from the ER]
  • Products shipped by the golgi apparatus: Proteins, Vacuoles
• PEROXISOMES

  • Structure: Smaller, spherical-shaped membrane-bound organelles formed from the ER or through fission contain oxidative enzymes
  • Major Functions: Detoxify specific harmful substances either produced by the cell or taken into the cell, Engage in beta oxidation of fatty acids to acetyl CoA, Contain oxidative enzymes
• CENTROSOME


  • Structure: Region near the nucleus from which microtubules sprout; Contains a pair of centriole
  • Major Functions: Organizes microtubules, Participates in mitotic spindle formation during cell division
• NUCLEOLUS


  • Large, prominent structure within the nucleus
  • Major Function: for synthesis of ribosomes
• CYTOPLASM


  • Responsible for many cellular processes
• ROUGH ER

  • Has ribosomes
  • Synthesis of secretory proteins, cell membrane protein and organelle protein
• ORGANELLES


  • Carry out specific metabolic activities of the cell
• LYSOSOMES


  • Structure: spherical-shaped membrane-bound organelles formed from the Golgi apparatus
  • Major Function: contain hydrolytic enzymes (required acidic pH) to digest proteins, polysaccharides, fats and nucleic acids, autophagy [process which the cells can recycle its own organic material], principal sites of intracellular digestion
• RIBOSOMES

  • Structure: organelles composed of both protein and ribosomal RNA (rRNA) that are organized into both a large and small subunit
  • Major Function: engage in protein synthesis
  • BOUND RIBOSOMES: Produce proteins that are secreted, incorporated into plasma membrane, and within lysosomes
  • FREE RIBOSOMES: Produce proteins used within the cell
• CYTOSKELETON


  • Structure: Organized network of protein filaments and hollow tubules
  • Microfilaments [determine the shape of cell for location], Intermediate filaments [mechanical strength], Microtubules [intracellular transport]
  • Major Functions: Provide mechanical strength to the cell, Establish cell shape, Locomotion, Intracellular transport of organelles
• Prophase

  1. The nucleolus disappears and the replicated chromatin condenses into discrete thread-like chromosomes

  2. The two centrosomes with their now-duplicated centrioles separate and migrate to opposite poles of the cell and organize the microtubules of the mitotic spindle

  3. Late in prophase, lamins and inner nuclear membrane are phosphorylated, causing the nuclear lamina and nuclear pore complexes to disassemble and disperse in cytoplasmic membrane vesicles
• Centrioles

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

  2. Replicate before cell division

  3. Organizing microtubules that serve as the cell’s skeletal system
• Flagella

  • Provide locomotion for the cell
  • Propels sperm
• Microvilli


  • Increase membrane surface area for greater absorption
• Interphase

  • Only the mitotic phase can be viewed under the light microscope
  • G1 – period in which cells accumulate the enzymes and nucleotides
  • S – period devoted primarily to DNA replication
  • G2 – short period of preparation for mitosis
• Anaphase

  Sister chromatids separate and move toward opposite spindle poles by a combination of microtubule motor proteins and dynamic changes in the lengths of the microtubules as the spindle poles move farther apart
• Cilia


  • Move substances over the cell surface (e.g. mucus and dissolved materials)
• Plasma Membrane


  • Phospholipid bilayer containing cholesterol and proteins (integral and peripheral) and some carbohydrates (externally)
  • Forms a selectively permeable boundary of the cell
  • Physical barrier to enclose cell contents
  • Regulates material movement into and out of the cell
  • Establishes and maintains an electrical charge difference across the plasma membrane
  • Cell communication
• Centrosome

  1. Region near the nucleus from which microtubules sprout; Contains a pair of centriole

  2. Organizes microtubules

  3. Participates in mitotic spindle formation during cell division
• Mitosis


  The only cell cycle phase that can be routinely distinguished with the light microscope
• Cell Cycle

  Eukaryotic cell – cell that has a true nucleus
• Metaphase


  1. Chromosomes condense further and large protein complexes called kinetochores

  2. The cell is now more spherical and microtubules move the chromosomes into alignment at the equatorial plate
• Telophase


  1. The two sets of chromosomes are at the spindle poles and begin reverting to their uncondensed state

  2. Microtubules of the spindle depolymerize and the nuclear envelope begins to reassemble around each set of daughter chromosomes

  3. A belt-like contractile ring of actin filaments associated with myosins develops in the cortical cytoplasm at the cell’s equator

  4. During cytokinesis at the end of telophase, constriction of this ring produces a cleavage furrow and progresses until the cytoplasm and its organelles are divided into two daughter cells
• Objective Lenses


  Metal cylinders attached below the nosepiece and contains especially ground and polished lenses
• Ocular or Eyepiece 


  Final image is viewed