Microscopy

How Do We Study Cells?

Microscopy

  • Technological developments are key to large increases in knowledge about cellular structures and functions.

A. Overview of Microscopy

  • Function: The primary function of microscopy is to enlarge tiny objects for examination in detail.

    • Magnification: Refers to the process of enlarging an object using lenses.

    • Resolution: Defines how close two objects can be and still be clearly seen as two separate entities.

    • Contrast: The ability to distinguish an object from its background, which is essential for visibility.

    • Blurriness Factor: Factors that may affect the clarity of the image being viewed.

Types of Microscopy

  1. Light Microscopy (LM)

    • Utilizes a light bulb to illuminate and observe objects.

    • Commonly used in biological studies to view live cells or tissues with proper staining to enhance visibility.

  2. Electron Microscopy (EM)

    • Uses electrons instead of light to examine objects, providing greater magnification and resolution.

    • Employs magnets to direct electron beams towards the specimen.

    • Two primary types of electron microscopy:

a. Transmission Electron Microscope (TEM)

  • This microscope transmits electrons through a specimen to form an image, allowing for high-resolution imaging of internal structures.

b. Scanning Electron Microscope (SEM)

  • This type scans the surface of a specimen with a focused beam of electrons resulting in detailed three-dimensional images of the surface.

B. Cell Fractionation

  • Cell fractionation is a technique associated with microscopy for the analysis of cellular components.

  • Homogenization: The process of breaking down cells to create a mixture known as "cell homogenate."

    • This process can be thought of metaphorically as a "cell milk shake".

Steps of Cell Fractionation

  1. Centrifugation: A technique used after homogenization, in which the cell homogenate is spun at high speeds.

    • The spinning creates a force that separates cellular components based on their density.

    • Pellet: The solid material that collects at the bottom of the tube during centrifugation, containing heavier components of the cell.

    • Supernatant: The liquid portion that remains above the pellet after centrifugation, containing lighter components and soluble materials.

    • Important note: During exams, remember to refer to "cell milk shake" when discussing homogenization and centrifugation processes.

    • Make sure not to confuse terms when describing the outcomes of these processes: Pellet vs. Supernatant.