On week 5, I learn about endosymbiosis and also cell cycle. In endosymbiosis, I can know about the endosymbiosis theory which is a new thing for me and also about mitochondria and chloroplast. There is also an evidence of endosymbiosis regarding mitochondria and chloroplast.
Endosymbiosis Theory :
- Eukaryotes is derived from prokaryotes
- Heterotrophic baecteria became mitochondria
- Cyanobacteria became chloroplast
- Host cell is a large eukaryotic cell
Evidence for Endosymbiosis :
- Both mitochondria and chloroplast are naturally from prokaryotes. This is because the organelles has circular DNA that does nothave introns (non coding protein) or histone whereas the eukaryotes have linear DNA and associated with histone proteins.
- The organelles also divide by binary fission which splits the cell into two.
- The organelles is a membrane bound organelle which has inner membrane and outer membrane. The inner membrane resemble prokaryotes while the outer membrane resemble eukaryotes.
CELL CYCLE
Next topic is I learnt about the cell cycle which I already know since in my secondary school. But, what makes this topic interesting is, there is cyclin that control the cell cycle and also Cdks which is a new topic for me.
Ordered set of events, resulting in cell growth and division into two daughter cells.
-> Multicellular cell is divide to replace lost or damage tissues and allow organisms to grow. Unicellular cell divide is to reproduce
Regulation of cell cycle :
Passage of cell through cell cycle is controlled by proteins in cytoplasm (cyclin)
- G1 cyclin (D cyclin)
- S-phase cyclin (cyclin A)
- Mitotic cyclin (B cyclin)
Cyclin-dependent kinases (Cdks)
The level of cell cycle become fluctuated with the activation of cyclin that is bind to the Cdks. Cdks will undergo phosphorylation that will add phosphate group to the protein substrates that control process in cell cycle.
- G1 Cdk (Cdk A)
- S-phase Cdk (Cdk B)
- M-phase Cdk (Cdk b)