Prokaryotes

Prokaryotic cells 

Prokaryotes include bacterium, these are smaller than eukaryote, and differ mainly as they have no nucleus or a nuclear envelope. Because of their small size (0.1-10 micrometres) this makes them very successful. Bacterium possess a cell wall which differs as it is made of murein rather than cellulose it is a polysaccharide combined with a polypeptide; murein doesn't stretch easily meaning that when osmosis occurs it resists activity. Bacterium further protect themselves by secreting a capsule of slime around its wall. 

Cell structure relating to its role: 

• CELL WALL- A physical barrier that excludes certain substances and protects against mechanical damage and osmotic lysis.
• CAPSULE- This protects bacterium from other cells and helps groups of bacteria stick together for further protection.
• CELL SURFACE MEMBRANE- Acts as a differentially permeable layer which controls entry and exit of chemicals.
• CIRCULAR DNA-This possess the genetic information for the replication of bacteria cells.  
• PLASMIDS- These posses the genetic information that may aid survival of bacteria in adverse conditions e.g. produces enzymes to breakdown antibiotics.
• RIBOSOMES- 70's (smaller than eukaryotes which are 80's) for protein synthesis
• FLAGELLUM- Used for locomotion.
• CYTOPLASM- Contains enzymes and soluble materials.  

Eukaryotes vs Prokaryotes 

Pro have no true nucleus just circular DNA within the cytoplasm wheres Eu have a distinct nucleus with a nuclear envelope. 

Pro DNA is not associated with proteins whereas in Eu histones are associated. 

DNA in Eu is linear and there are no plasmids whereas in Pro there are plasmids.

Only Eu contain membrane bound organelles e.g. mitochondria. 

Pro have smaller ribosomes (70's) compared to 80's of Eu.

cell wall made of meurin in Pro whereas cellulose in Eu, and Pro also contains capsule.