[TOPIC 2] Cell Wall and Membrane Structure of Prokaryotes

Assalamualaikum w.b.t. 

For this topic, I think it is crucial to be able to differentiate between Gram-positive and Gram-negative organism's cell wall properties. 

Other than knowing the difference of the two type of cell walls, it is also important to know the functions and significance of each substances contained in the cell walls. For instance, teichoic acid in Gram-positive organisms and LPS in Gram-negative organisms actually have the same function in which the components contribute to the cell's antigenic specificity. 

Other than knowing the difference and functions of Gram-positive and Gram-negative cells, this topic also covers on the difference between bacteria and archaea. 

So, how to remember the cell wall visual? 
Remember the spaghetti and meatballs picture! :D 

You don't remember? 

Wait. 

I was talking about the above picture! :D 

Why are we focusing on distinguishing bacteria from archaea? 

I would say that it is because this two organisms are in the category of prokaryotes (because they do not have true nucleus and membrane bound organelles) while the other group of microbes are eukaryotes. 

Some of the differences between the two organisms that I think I should note on are : 
- The presence of peptidoglycan 
- The amino acid contained in them 
- The glycosidic bond between the sugars 
- Ester/Ether link 

Other than that, I also learned some new terms. What are they, you ask? 

It's spheroplast and protoplast! 

Protoplast is a cell that has be lysed but it is still capable of carrying out metabolism processes. 

Spheroplast is a cell that have not been completely lysed, thus some of the components of cell wall still remains. 

How do they formed? 

Spheroplast are constructed when the the cell wall has been acted on by the lysozyme, but it is not completely hydrolysed. 

Below are some of the questions that were discussed in class throughout the lesson : 

1. How does glycocalyx act as a source of nutrients?
--> What I found on the net is an example of organism, Streptococcus mutans use glycocalyx as its source of nutrient when energy storage is low. This organism has glycocalyx in the form of capsule and it will break down the glycocalyx and utilise the sugar since glycocalyx is made up of sugars called EPS. 

2. Movement of bacteria towards nutrients or a particular substance is called 'chemotaxis'. 

3. The conjugation of pili is a process where transfer of DNA occurs. However, it does not contribute to the production of new daughter cells. Instead, the plasmid contains specific genes such as resistance to a certain antibiotic and ability to produce enzyme. Thus, the recipient of the DNA transfer will obtain the traits of the donor. 

#Do remember that the transfer of DNA can only occur between the same species! 

4. How is cell wall serve as a site of action for antibiotics? 
Antibiotics have a certain mechanism to attack cells such as attacking the cell wall, nucleic acid, ribosome etc. When antibiotics attack the cell wall, the cell wall will lyse or rupture causing the content to leak out and the organisms will die. 

That's all from me~