TOPIC 3 - PROKARYOTES

*INCLUDE WHAT HAVE WE have DONE IN CLASS ALSO

This new entry is for the next topic, Prokaryotes which is topic 3. Before we started to learn topic 3 we all have to do a mindmap on Porkaryotes. It turns out my mindmap is like this;


I have done my best on this mindmap. I put up all that I know into this mindmap. I tried to cramp all the information that I gather about prokaryotes and make a mindmap. 

MINDMAP ON PROKARYOTES

Basically the word prokaryote comes from the Greek πρό (pro) "before" and καρυόν (karyon) "nut or kernel". Prokaryotes are organisms whose cells lack a nucleus and other organelles. Prokaryotes are divided into two distinct groups; the bacteria and the archaea. which scientists believe have unique evolutionary lineages. Most prokaryotes are small, single-celled organisms that have a relatively simple structure. Prokaryotes are called prokaryotic cell.

The learning outcomes for this topic are;
1. To explain, describe, and identify the important structure of prokaryotic cells
2. To explain the characteristics or functions of the structures of prokaryotic cell

PROKARYOTE

This is the basic structure of prokaryotic cell. The size of prokaryotic cell range from 0.2-2.0 um (diameter) and 2-8um (length). prokaryotic cells lack membrane-bound nucleus, cytoskeleton, membrane-bound organelles and internal membranous structures such as endoplasmic reticulum and Golgi apparatus.

There are common bacterial & archaeal structures and their functions

1. Plasma membrane - Selectively permeable barrier, mechanical boundary of cell, nutrient and waste transport, location of many metabolic processes such as respiration and photosynthesis), detection of environmental cues for chemotaxis
2. Gas vacuole -  Buoyancy for floating in aquatic environments
3. Ribosome - Protein synthesis
4. Inclusion - Storage of carbon, phosphate and outer substances
5. Nucleoid - Localisation of genetic material
6. Periplasmic space - Gram positive bacteria: contain hydrolytic enzymes and binding proteins for nutrient processing and uptake ; Gram negative bacteria and archea: small or absent of periplasmic space
7. Cell wall - provides shape and protection from osmotic stress
8. Capsules and slime layers - Resistance to phagocytosis, adherence to surgaces (also presence in archea)
9. Fimbriae and pili - Attachement to surfaces, bacterial conjugation and transformation, twitching and gliding motility
10. Flagella - swimming motility
11. Endospore - survival under harsh environmental conditions (only observed in bacteria)

In this topic we learned about components of prokaryotic cell which is;

1. structure external to the cell wall
2. cell wall 
3. structure internal to the cell wall

The structures external to the cell wall are:

 GLYCOCALYX

• Glycocalyx is a coating secreted by the bacteria. It composed of polysaccharide, polypeptide or can be both. The chemical composition of glycocalyx varies with species. It also hase different terms depending on the structure. 

> Gelatinous -  glycocalyx
> Organized and firmly attached to cell wall - capsule
> Unorganized and loosely attached - slime layer




The functions of glycocalyx are for;

• attachment to surface
• protect against dehydration
• inhibit movement of nutrients out of cells
• source of nutrient

 

 FLAGELLA