Prokaryotes

Question 1

Gram staining process

Answer 1

• Prepare culture wet mound
• Drop of violet dye and iodine colours culture
• Culture rinsed with alcohol
• Drop of safranin added to culture

Question 2

Function of Cell Wall

Answer 2

• Gives cell shape
• Prevents bursting of cell in a hypotonic environment
• Protects the contents of the cell

Question 3

Structure of the Cell Wall

Answer 3

• Peptidoglycan which links other molecules to the surface

* Lipopolysaccharide layer

Question 4

Uses of Gram staining

Answer 4

• Determine whether a bacteria is gram + or gram negative bacteria
• Gram - bacteria is more toxic (dangerous) because it’s lipopolysaccharide layer protects it from attacks from the immune system
• Also more resistant to antibiotics

Question 5

Shape of bacteria

Answer 5

• coccus (spherical)
• bacillus (rod shape)
• spirillum (coiled)
• vibrio (comma shaped, gram - bacteria)

Question 6

Layers surrounding cell wall and their structure

Answer 6

• Capsule and slime layer
• Capsule well defined and dense, slime layer not that organised
• Both made up of polysaccharide or proteins
• layers allow prokaryotes to stick to other substances
• Protects against dehydration

Question 7

Internal Organisation (organelles inside prokaryotes)

Answer 7

• Ribosomes: responsible for the manufacturing of proteins
• Cell Wall: Protects the cell
• Plasma membrane: Controls the entry and exit of substances in the cell
• Plasmid: Controls the production of pili, carries accessory genes

Question 8

Differences between Prokaryotes and Eukaryotes

Answer 8

Prokaryotes; Eukaryotes
Genome less DNA; Genome more DNA
Circular DNA; linear DNA
Chromosomes associated with less proteins; Chromosomes associated with proteins
Nucleotide; Nucleus
Rings of DNA; DNA strands

Question 9

Endotoxin vs exotoxin

Answer 9

• Endotoxin; exotoxin

• Released by Gram - bacteria; gram + bacteria
• Streptomycin effective against it; Penicillin effective against it
• ; can be used for immunisation by modifying toxoids (inactive portions)
- Gram -; Gram +

• St

Question 10

Gram + bacteria v Gram negative bacteria

Answer 10

+:

• Peptidoglycan and plasma membrane
• More peptidoglycan
• Simple Walls

-:

• Complex Walls
• Less Peptidoglycan
• Lipopolysaccharide layer above the peptidoglycan layer and plasma membrane

Question 11

Fimbraie, pili, flagella

Answer 11

Fimbriae
• Appendages surrounding the lipopolysaccharide layer of cell
• Used to stick to cells

Pili
• Structure that attaches one cell to another at beginning of conjugation

Flagella
• appendage used for movement

Question 12

Endosymbiotic Theory

Answer 12

• Eukaryotes developed from prokaryotes
• Mitochodria and chlorplast used to be endosymbiotic prokaryotes, bacteria found within the cell
• Host receives energy, symbiont receive protection

Question 13

Evidence for endosymbiotic theory

Answer 13

• 2 different membranes
- similar to prokaryotes, mitochondria and chloroplasts have double membrane
• Size
- similar to free-living prokaryotes
• Cristae
- similar enzymes and transport systems
• Ribosomes
- biochemical composition similar to prokaryotes
• DNA
- like eukaryotes, tRNA present
• Division
- similar to prokaryotes, reproduction by cell spliting
• DNA replication
- like prokaryotes, circular DNA not associated with other proteins