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Lecture 3: Anatomy of Eukaryotes and Endosymbiotic Theory

External structure of Eukaryotic Cells

Glycocalyces – only present in no-cell wall cells, ie, protozoans and animal cells – itis sticky carbohydrate anchored within the cytoplasmic membrane through covalent bonds with membrane proteins and lipids compared to prokaryotes, glycocalyces are not as structurally organized as the capsules in prokaryotes

Cell walls – found in fungi, algae, plants, and some protozoa, it provides shape, support against osmotic pressure. Contains polysaccharides and differs among the different types of eukaryote:

  • plants (cellulose*)
  • fungi (cellulose, chitin* (also found in exoskeleton of insects), and/or glucomanna)
  • algae (varying chemicals like cellulose, proteins, agar, carrageenan, silicates, algin, calcium carbonate, or a combo of these substances among different algae)

*Note: closely related sugar in structure and has glycosidic bonds

Cell surface markers – marker proteins found at the surface of the cell and in unique to every family sharing similar receptor. Antibodies recognize an antigen. The antigen is then coated with these antibodies which recognizes the antigen by the antigen’s surface markers. This is how the antigen is killed.

  • each cell has different cell markers
  • some markers are species related
  • some markers are unique to only one specie

EXAMPLE: In humans, we have some proteins that are shared by some cell markers. Blood for instance, has a O, A, B or AB blood types. On the red blood cell (RBC), there is an antigen that sticks out (either A or B, one without an antigen sticking out is an O blood cell).

  • O – universal donor
  • A or B – universal recipients

If blood A is given to blood type B person, the A & B blood cells would coagulate leading to clots that can cause strokes, which most likely will end in death! Hence, check out your blood type and also consider donating blood. Blood banks can only store human blood for a small amount of time and continually needs new donors.

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The former contents were notes taken from Professor Phil Hawkins at Foothill College Bio 41 in Winter 2010. Additional information are also taken from the textbook: Microbiology with Diseases by Taxonomy, 2nd edition, by Robert Bauman.

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