Cytology

1
Cytology

• A Brief Study of Cells

2
Discovery of Cells

• Research greatly aided/accelerated by use of
  microscopes
• Hooke published drawings in 1665
• Anton van Leeuwenhoek studied microscopic
  materials with hand lens
• Schleiden (1838)--botanist (plant biologist) made
  generalization that all plants made of cells
• Schwann--generalized that all organisms have
  cells
• Virchow--(1850) said that cells come from
  pre-existing cells

3
The Cell Theory

• Cells are the basic unit of life (smallest unit
  of life that can carry out functions of life)
• All organisms are made up of one (unicellular) or
  more cells (multicellular)
• All cells come from pre-existing cells

4
Types of Microscopes

• Light microscope--uses environmental (room) light
  to magnify objects 100x - 1000x (100x - 430x for
  our microscopes)
• Compound microscope--contains more than one
  objective (magnification power)
• Dissecting microscope--used to view larger
  objects in 3-D magnifies 10x - 20x
• Binocular--contains 2 eyepieces (one for each
  eye)
• Monocular--contains 1 eyepiece

5
Electron (and other) Microscopes

• Magnify hundreds of thousands of times
• Uses beam of electrons
• Requires specimen to be dead
• Scanning EM (SEM)--scan outstide of object and
  produce 3-D image
• Transmission EM (TEM)--pass electrons through
  sample
• SIAM--higher resolution, which may allow study of
  individual molecules.

6
Prokaryotes / Eukaryotes

• no nucleus
• no separate organelles
• only bacteria
• evolved first
• Smaller cells

• nucleus
• many organelles
• all other cells/organisms
• evolved from prokaryotes
• Larger cells

7
Prokaryotes / Eukaryotes

• Common Characteristics
• cell membrane
• cytoplasm
• ribosomes

8
Cell makeup

• Cell Membrane--surrounds the cell
• Cytoplasm--everything in the cell between the
  membrane and the nucleus
• Made primarily of water and organic compounds
• Organelles (little organs)--small structures in
  the cytoplasm that carry out specific tasks
• Cytoskeleton--network of protein fibers and tubes
  in cytoplasm
• Give the cell structure
• Facilitate movement for some cells (ameba)
• Nucleus--control center of cell (contains
  chromosomes that are made of DNA)
• Surrounded by double membrane (nuclear envelope)

9
Cell Membranes

• Separates the cell from the world around it
• Semi-permeable (some things go through)
• Phospholipid bilayer--made of glycerol, two fatty
  acids, phosphate
• Phosphate is hydrophilic (water-loving)
• Lipid tails are hydrophobic (water-fearing)
• Proteins embedded in membrane facilitate movement
  of things through membrane
• Fluid in nature--lipids and proteins in
  constant motion (fluid mosaic model)

10
Movement across cell membrane

• Diffusion--movement of molecules from an area of
  high concentration to area of low concentration
• Osmosis--diffusion of water across a
  semi-permeable membrane

11
Organelles

• Mitochondrion--powerhouse of cell site of
  cellular respiration
• Ribosomes--assemble proteins
• Endoplasmic reticulum (ER)
• Rough or smooth ER (w or w/o ribosomes)
• Detoxify and transport substances
• Golgi apparatus--packaging and secretion
• Lysosomes--contain digestive enzymes

12
Organelles

• Nucleus--control center of cell (DNA)
• Nucleolus
• Inside nucleus
• Site of ribosome production
• Nucleoplasm--material inside the nucleus
• Vacuoles/vesicle--stores H20, undigested food,
  wastes
• Centrioles--aid in cell division

13
Plant Cells

• Plant cells also have
• Chloroplasts--site of photosynthesis (type of
  plastid)
• Cell wall--surrounds membrane--provides
  support/rigidity
• Vacuole--much larger

14
Cells Moving about

• Extensions of cytoskeleton allow movement
• Cilia (cilium)
• Occur in large numbers
• Freshwater organisms use for movement / eating
• Also in our trachea for removing debris
• Flagella (flagellum)
• Long whip-like projections (tail)
• Prokaryotes move like propeller, eukaryotes move
  in whip-like motion