Cell Structure and Microscopy

• Three types of solutions:

  1. Hypertonic: higher solute concentration, causing cell shrinkage
  2. Hypotonic: lower solute concentration, causing cell swelling
  3. Isotonic: stays the same
• Endocytosis: Cell engulfs materials by forming vesicles from the cell membrane, bringing them into the cell.

  vs.

  Exocytosis: Cell expels materials by fusing vesicles containing the materials with the cell membrane, releasing them outside the cell.
• • Cell Theory: All living organisms are composed of cells, which are the basic units of life, and cells arise from pre-existing cells.
  • Spontaneous Generation: Disproved idea that living organisms can arise from non-living matter, which contradicts Cell Theory's principle of cells arising from pre-existing cells.
• Compound Microscope: Uses visible light and lenses to magnify specimens. Limited resolution.

  vs.

  Electron Microscope: Utilizes beams of electrons for higher resolution imaging, surpassing the limitations of light microscopes.
• Prokaryotes (bacteria): Lack a nucleus and membrane-bound organelles, simpler in structure.

  vs.

  Eukaryotes (animals, plants): Contain a nucleus and membrane-bound organelles, more complex in structure.
• Microscope

  A) Ocular Lens (10x)

  B) Ocular Tube

  C) Revolving Nosepiece

  D) Low Power Objective (4x)

  E) Medium power Objective (10x)

  F) High Power Objective (40x)

  G) Stage Clips

  H) Diaphragm

  I) Lamp/Light source

  J) Arm

  K) Stage

  L) Coarse Focusing Knob

  M) Fine Focusing Knob

  N) Base

  
• Ocular tube


  Holds the eyepiece for observing the specimen
• Revolving nosepiece


  Holds and rotates the objectives for changing magnification
• Objectives


  Lenses that magnify the specimen at different levels
• Stage clips


  • Hold the specimen slide in place on the stage
• Diaphragm


  Controls the amount of light passing through the specimen
• Lamp/Light source


  Illuminates the specimen
• Arm


  Supports the microscope and connects the base to the head
• Stage


  Platform where the specimen is placed
• Coarse-focusing knob


  • Moves the stage up and down for focusing at low power
• Base


  Supports the microscope and provides stability
• Fine Focusing Knobtunes the focus for medium and high power
• Microscope

  • The invention of the microscope allowed scientists to discover that cells existed
  • Scientists stain cells with dyes to see them better
• Compound Light Microscope

  • Utilizes Glass lenses and visible light to magnify images
  • Can magnify 1000x the actual size
• Electron Microscope (SEM)

  • Utilizes magnets and electrons to magnify images
  • Can magnify 500000x the actual size
• Scanning Tunneling Electron Microscope


  Can magnify living cells
• Cell

  • Basic structural and functional unit of all living things
  • Trillions and trillions of cells in the human body
• Cell Theory

  • All organisms are composed of one or more cells
  • The cell is the basic unit of structure and organization of organisms
  • All cells come from preexisting cells
• History of Cell Theory

  • Mattias Schleiden concluded that all plants are composed of cells. (1838)
  • Theodor Schwann declared that all animal tissues were made up of cells
  • Physician Rudolf Vichow proposed that every cell came from a cell that already existed through cell division
• Prokaryotic Cell

  Simple cell structure without a nucleus or membrane-bound organelles; with plasma membrane (ex. bacteria)
• Eukaryotic Cell

  Complex cell structure with a nucleus and membrane-bound organelles; with plasma membrane (Ex. animal/plant cells)
• Plasma membrane:

  • Thin, flexible boundary between the cell and its environment
  • Controls movement of nutrients into the cell and waste out of the cell
  • The plasma membrane is selectively permeable, and differentiates between different types of molecules
• Eukaryotic cells:

  • Have membrane-bound organelles
  • Can be multicellular or unicellular
  • Nucleus

  vs.

  Prokaryotic cells:

  • No membrane-bound organelles
  • Bacteria
  • Unicellular
• Phospholipids Bilayer

  • Composed of glycerol, fatty acid chains, and a phosphate group
  • Allows other molecules to float in the plasma membrane
• Proteins

  Transmit signals, provide support, and allow substances to enter and leave the cell
• Cholesterol

  Prevents fatty acids tails from sticking together
• Carbohydrates


  Identify chemical signals
• Nucleus

  Controls the cells activity
• Nucleolus

  Produces rRNA and assembles ribosomes
• Chromatin

  • Condenses to form chromosomes during cell division
  • DNA bound to proteins
• Nuclear Envelope

  Contains pores for transport
• Mitochondria

  • Produces ATP (chemical energy) through aerobic cellular respiration
  • The inner membrane is filled to increase surface area into extensions (cristae)
• Golgi Apparatus

  • Packages proteins for secretion
  • Secretes carbohydrates
  • Produces glycoproteins
• Lysosomes

  • Contains and isolate digestive enzymes
  • Prevent digestion of the rest of the cell
  • It might empty its contents into one membrane-lined vacuole containing a worn-out organelle
• Centrioles

  • Produce microtubules for cell division
  • At cell division, they migrate to opposite poles of the cell