Prokaryotes And Eukaryotes

Question 1

How do prokaryotic cells differ from eukaryotic cells

Answer 1

cells size
cell structure and composition
cell wall
organelles
Packaging of genome
genome complexity
ribosomes
flagella

Question 2

Cell wall differences

Answer 2

Eukaryotes:
- Cellulose (carbohydrate:plants and most algae)
- chitin (N-acetylglucosamine;fungi)

Prokaryotes:
- Bacteria: Peptidoglycan (N-acetylglucosamine + N-acetylmuramic)
- Archaea: Pseudo-PG, S-layer

Question 3

The bacterial cell wall and cell envelope

Answer 3

• Is very important for us and the bacteria. It is important in the characterisation of bacteria (Gram and Acid fast) - also a major target for antibiotics
• Helps differentiate between ground positives and ground negatives

Question 4

Comparison of bacteria cell envelopes

Answer 4

Look at notes for diagram

• The cell wall is only the rigid layer but the envelope is both the inner membrane and the cell wall and when they have an outer membrane that is also included as well.
• Outer membrane (can have porins) is very protective of what it lets into the Peptidoglycan.
• LPS they are very immunogenic and found in ground negatives
• MDR - take compound from the inside and pump them back out into the environment
• positive does not have outer membrane but has thin PG layer - it is simpler and it means that antibiotics will target the PG more than anything
• Arabians gala at an makes a thicker cell wall in general
• Mycolic acids can be very immunogenic but also can provide protection because they provide an outer waxy coat in top of the outer membrane so considered very impenetrable so things are difficult to get in or out
• Diatoms are algae that live in houses made of glass (silica)
• they are the only organism on the planet with cell walls composed of transparent , opaline silica.
• Cell walls can be used to distinguish between eukaryotes and prokaryotes. And between a eukaryote and a eukaryote. As well as between a prokaryote and a prokaryote.

Question 5

LPS

Answer 5

Lipopolysaccharides, lipids with attached sugar polymers

Question 6

LTA

Answer 6

Lipo-teichoic acids, polyalcohols embedded in the cell wall

Question 7

MA: Mycolic acids, very long, branched chain fatty acids

Question 8

Koch’s postulates have their limitations and there are many exceptions:

Answer 8

Koch’s postulates have their limitations and there are many exceptions:
for example:
The cause of leprosy (mycobacterium leprae) cannot be “grown in pure culture” in the laboratory: a virus cannot be grown outside a hist cell
viruses cannot replicate outside the host cell
there may be other pathogens for which there are no animal models

prokaryotes are all around us, are the dominant organisms on the planet and inhabit every environment
microbial habitats vary enormously and so do organisms within them

Question 9

Koch’s postulates

Answer 9

1. The suspected pathogen must be present in all cases of the disease and absent from healthy animals
2. The suspected pathogen must be grown in pure culture
3. Cells from a pure culture of the suspected pathogen must abuse disease in a healthy animal
4. The suspected pathogen must be re isolated and shown to be the same as the original