Eukaryotic Cells

Microscopy
1. Parts & Functions
  1. Condenser
    1. Focuses light onto the specimen
  2. Iris Diaghragm
    1. controls the amount of light entering and leaving the sondenser
  3. Coarse & fine controls
    1. For focusing
  4. Objective lens
    1. provides the first magnified image
  5. eye piece
    1. magnifies the image and presents it to the viewer
  6. resolving power
    1. its ability to distinguish between two points that are close together
2. working out the size of the specimen
  1. For high power, one small division on graticule is 2.5micrometers
  2. For medium power, one small division is 10micrometers
  3. for low power, one small division is 25 micrometers
3. electron microsope
  1. has a much higher resolving power
  2. electrons are emitted at the top and travel through a vacuum in the column of the microscope. The TEM (transmission electron microscope) uses elecrtrogmagnetic lenses to fu=ocuse the electrons into a very thin beam.
  3. there are two types of electron microscope, TEM and scanning electron microscope (SEM). the electrons pass through a thin section of the specimen in a TEM on they way to the photographic film. some electrons are scattered and siapper from the b.eam depending on ttheir density. at the bottom of the un-scattered electrons hit a flourescent screen, which gies rise to a 'shadow' image of the specimen with its different parts displayed in waried darkness according to their density. the images are called electron micrographs
  4. they can produce images with magnification of up to 500 000
  5. In SEM's, the electrons are reflected off the prepared surface of the specimen
Organelles
1. all living organisms are eukaryotes (plant,animal, fungi and protoctist kingdoms)
2. much larger than prokaryotes, have less surface area per volume. they are compartmentalized, containing organelles that perform specific functions
3. they all have a cell membrane and a nucleus, surrounded by a nuclear encelope
4. The Nucleus and ribosomes
  1. diameter of 5micrometers. contains chromatin which is a threadlike material that coils into chromosomes just before cell dicision occurs. it consists of DNA and protein
  2. nucleolus is a dark region of chromatin inside the nucleus, it is the site where rRNA joins with proteins to form ribosomes
  3. the nucleus is separated from the cytoplasm by the nuclear membrane, which contains pores to permit the passage of substances
  4. ribosomes are the site of protein synthesis in the cell, they may occur freely or in groups as polyribosomes
  5. a series of intracellular membranes compartmentalise the cell.: thenucleus, the membranes of the ER and the golgi apparatus, and several types of vesicles
5. Endoplasmic Reticulum
  1. system of cisternae (flattened vesicles) continuous with the outer membrane if the nuclear envelope
  2. the rough ER is studded with ribosomes on the cytoplasm side, it is the site where proteins are synthesized and enter the ER interior for processing and modification
  3. the smooth ER is continuous with rough ER, but lacks ribosomes, it is a site of the manufacture of lipids and steroids
6. Golgi Apparatus
  1. consists of a stack of slightly curved cisternae
  2. it receives protein-filled vesicles that bud from the rough ER and lipid filled vesicles from the smooth ER
  3. enzymes within the golgi apparatus modify the carbohydrates that were placed on the proteins in the ER, proteins and lipids are sorted and packaged
  4. vesicles formed from the membrane of the outer face of the golgi apparatus move to different locations in a cell, at the plasma membrane they discharge their contents as secretions, a process called exocytosis
  5. protein degradation is essential to the cell to supply amino acids for fresh protein synthesis, to remove excess enzymes, to remove transcription factors that are no longer needed. there are two major intracellular devises in which damaged proteins and broken down: lysosomes and proteasomes
7. Lysosomes
  1. membrane-bounded vesicles produced by the golgi apparatus. they contain powerful digestive enzymes
  2. lysosomes deal primarily with extracellular proteins, cell-surface membrane proteins, the proteins engulfed by WBC
  3. macromolecules enter a cell by vesicle formation; lysosomes fuse with vesicles and digest the contents of the vesicle
  4. WBC use lysosomes to digest bacteria
  5. autodigestion occurs when lysosomes digest parts of cells
  6. participate in apoptosis
8. proteasomes
9. Centrioles
10. Vacuoles
11. Cell Wall
12. Secretoy Vesicles
13. Microtubules
14. Cilia and Flagella
15. Chloroplasts
16. Mitochondria
Cell Membranes

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