PROKARYOTES EXTERNAL



Hello and welcome guys, so this week we basically learned more details about prokaryotes external.
In this topic, we must know what the meaning of prokaryotes. Prokaryotes is a group of organisms that have lack of nucleus and membrane-bounded organelles. Prokaryotes have 2 domain which are Bacteria and Archaea. In this topic, we must be able to describe the structure and functions of the structure of prokaryotes. Basically prokaryotes have three basic shape which is cocci (s. coccus), bacilli(s. bacillus)and spiral.


In the class, we discuss about the relationship of size-shape of this prokaryotes. So the relationship are that the bigger the size, the better it to adapt to extreme environment condition and also the bigger the size, the larger the food storage of the cells.


Prokaryotes



There are four structure external to the cell wall, there are glcocalyx, flagella, axial filaments and pili/fimbriae. A glycocalyx is made of sugars is called an extracelluar polysaccharides (EPS). It a substance that surround the cell. the substance that are organized and firmly attached to the cell wall is capsules. The substance that unorganized and loosely attached the cell wall is called slime layers.The function of glycocalyx are to protect from phygocytosis, able to attach to various surfaces, it is a source of nutrients and protects a cell against dehydration. Next, flagella. Flagella is a threadlike, loccomotor appendages extending outward from plasma membrane and cell wall. There are several type of motility. there are "run"or "swim", "tumbles" and "swarm'.




Axial filament



Fimbriae & pili


Axial filaments is a bundles of fibrils that arise at the end of the cell beneath the outer sheath. It present in a spirochetes group of bacteria. Lastly. fimbriae/ pili. The hairlike appendeges that are shorter , sstraighter and thinner than flagella. The difference between fimbriae and pili are that pili are more longer than fimbriae and pili  joint bacterial cells in preparation for the transfer of DNA from one cell to another and sometimes it called sex pili.

We also discuss about the differece of bacteria and archaea. The archaea do not contain peptidoglycan while bacteria contaion peptidoglycan. Also archaea have ether bond while bacteria have ester bond.
We also discuss abouth the Gram-positive and gram-negative of cell wall. Gram positive contain teichoic acid while gram negative do not contain teichoic acid. Gram positive secreted excoenzyme.


Gram positive





peptidoglycan structure- Gram negative

I think thats all that I can share to you. I will update more next week for our next topics. Bye and see yaa.........








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