Intracellular structures of prokaryotes

1) Plasma membrane

•  Anchoring to cytoskeleton to provide shape to the cell
• Similarities between simple diffusion and facilitated diffusion

 

Similarities between simple diffusion and facilitated diffusion
·       Down the concentration gradient ·       No energy is required
Simple diffusion	Facilitated diffusion
·       Through the phospholipid bilayer	·       Through the transport protein
·       Happens to the small and non polar particles	·       Happens to large and polar particles

• Condition of cells in different type of solutions

	Hypertonic solution	Isotonic solution	Hypotonic solution
Animal cell	Shrink	No net movement of water	Burst
Red blood cell	Crenation	No net movement of water	Haemolysis
Plant cell	Plasmolysis	No net movement of water	Deplasmolysis

 - Application of osmosis in our body:

• Osmoregulation in Amoeba sp. and Paramecium sp.
• Plant wilting (excess fertiliser cause hypertonic soil, water diffuse from root cell to the soil, plasmolysis occur)
• Food preservation (salted fish and pickles)

- Group translocation

• Active transport.
• A mechanism utilised by bacteria to transport a compound into their cell by allowing the compound to bind with protein in plasma membrane, altering its chemical structure during passage across the membrane.
• Example : Phosphotransferase system (PTS) , method used by bacteria for sugar uptake and the source of energy is from phosphoenolpyruvate
• PTS include enzyme I and enzyme II which is substrate specific.
• Modified carbohydrate in the cytoplasm is chemically different compare to carbohydrate outside. Hence carbohydrate will be always transported down the concentration gradient.

2) Cytoplasm

• Act as a buffer to protect genetic material of cell
• Prokaryotes does not have cytoskeleton

3) Plasmid

• Extrachromosomal genetic material which are not contain of important genes for metabolism
• Example: Gene for drug resistance
• Can be transferred to another bacteria through conjugation

4) Ribosomes

•  Comparison of ribosome between prokaryotes and eukaryotes

Prokaryotes	Eukaryotes
N- formylmethionine as starter for amino acid	Methionine as starter for amino acid
50 S + 30 S = 70 S	60 S + 40 S = 80 S

• Svedberg unit refer to sediment coefficient, in other words speed of centrifugation.
• In prokaryotes, both 50S and 30 S subunit exist separately in cytoplasm until the small subunit recognize and bind to specific mRNA. The larger subunit is now come and form a complete ribosome.
•  Suspended in cytosol is known as freely ribosome
• Bound to endoplasmic reticulum is known as attach ribosome

5) Metachromatic granules

• Also known as volutin
• Function: Storage for inorganic phosphate for generation of energy
• Large
• Found in eukaryotes as well

6) Sulphur granules

• Appear as bright, slightly yellow spherical area in cell
• Energy reserve
• Common in bacteria that use hydrogen sulphide or thiosulphate as electron source

7) Carboxysomes

• Two types: alpha carboxysomes and beta carboxysomes
• Contain two enzyme: ribulose-1,5-biphosphate carboxylase and carbonic anhydrase 
• Used for carbon dioxide fixation during photosynthesis
• The structure is made up of many layer to prevent the carbonic anhydrase diffuse out of the carboxysomes

8) Magnetosomes

• Contain iron oxide which is also known as magnetite
• Allow the bacteria to orient and navigate along the magnetic field
• Lastest finding of a new bacteria BW-1 can produce both greigite and Magenetite

9) Why the smaller the gas vesicles, the lesser the buoyancy, the stronger the cell?

• This is because the lesser the buoyancy, the cell will sink more deeply in the lake.
• The deeper it sink, the greater pressure that it withstand, the stronger it is.

10) Lipids inclusions

• Also known as lipocytes and fat cells
• Two types: White fat cells and brown fat cells

structure of adipocyte

White fat cell	Brown fat cell
Single lipid droplet	Small lipid droplet
No mitochondria	High number of iron containing mitochondria
Cannot generate heat but it does insulate the body	Generate heat by burning calories
Found under the skin	Deposits around vital internal organ and along back and sternum



Difference between brown adipose tissue and white adipose tissue



White fat cells

 

11) Endospore

structure of endospore

Structure	Function
Exosporium	-          Outermost layer -          Additional glycoprotein layer -          Cover spore coat
Spore coat	-          Made up of protein -          Provides chemical and enzymatic resistance
Cortex	-          Needed for dehydration of the spore core, which aids in resistance to high temperature
Germ cell wall	-          This layer of peptidoglycan will become the cell wall of the bacterium after the endospore germinates
Core	-          Exist in a very dehydrated state -          Houses DNA of cell
Small acid soluble proteins (SASPs)	-          Tightly bind and condense the DNA -          Change the conformation of DNA into Z conformation -          Responsible for resistance to UV light, desiccation and DNA damaging chemicals