WEEK 4- CELL THEORY AND PROKARYOTE, VIRUS, VIROID AND PRION

During fourth week, I learnt about cell theory, prokaryotic cell, virus, viroid and prion. This topic is very familiar to me because of my diploma background and help me recalling and installing my memory about basic microbiology. The Cell Theory is one of the basic principles of biology. Credit for the formulation of this theory is given to German scientists Theodor Schwann, Matthias Schleiden, and Rudolph Virchow.The Cell Theory states: 1)All living organisms are composed of cells. They may be unicellular or multicellular. 2)The cell is the basic unit of life. 3)Cells arise from pre-existing cells. Cell divided by two Eukaryotic and prokaryotic cell.

The first diagram is for 2 basic type of cell, the first picture is prokaryotic cell and the second one is eukaryotic cell. These two has a few similarities and a lot of diffrences.

I also learnt about the bacterial shape.

Another things that I learnt is about virus, viroid and prion. Virus is something unique that being held between living and non-living thing. It require host cell to show the living thing proterties and I learnt about the properties of virus, classification of virus and how the reproduce.

These picture are the example for virus (HIV virus and Bacteriophage). They consist of 2 major part which are protein coat and heredity material (either DNA or RNA). Below, is the life cycle for virus. Without the host, they can't show the virulency. To maintain their existence, they undergo lysogeny and lytic cycle. For lysogeny, they remain dormant until suitable condition before the lytic occur.

Viroid is a smallest infectious pathogens known, consisting solely of short strands of circular, single-stranded RNA without protein coats. Viroid is a plant virus.

The potato is one of the example of viroid infection. Another thing I learnt is prion. Prion is infectious protein that effect nervous system. Prion causes mad cow disease, kuru, scrapie. It is dangerous.

The cow that being infected by Prion. Mad cow disease (BSE).

Another example for prion infection- Creutzfeldt-Jakob disease. For this week topic is really broad. What I learnt this week is just basic. I need to read a lot about this topic from different sources.