Prokaryotes

Question 1

Prokaryotes

Answer 1

• a microscopic single-celled organism which has neither a distinct nucleus with a membrane
  nor other specialized organelles, including the bacteria and cyanobacteria

Question 2

General characteristics

Answer 2

• Fall under Monera -> Archaea and Eubacteria
• First forms of life that assisted in the changes that allowed for more complex forms of life to
occur
• Can adapt to live in almost any environment and therefore are the most abundant
organisms on earth

Question 3

Gram stain technique:

Answer 3

• 19th cen. Hans Christian Gram (Danish)
physician
• Categorizes bacterial species according to
differences in cell wall composition
Technique:
• Culture bacteria
• Wet mount à sample onto a slide
• Stain with crystal violet + iodine à dark
blue/violet
• Alcohol rinse
• Counterstain with red dye safranin

Question 4

Structural and functional adaptations:

Answer 4

• Unicellular
• Small between 0.8-8μm
• 3 main shapes:
o Spherical -> Cocci

§ Diplo-, strepto-, staphylo-
o Rod-shaped -> Bacilli

o Spiral -> Spirilla

Question 5

Results of staining

Answer 5

• Structure of bacterium’s cell wall determines
the staining response
1. Gram-positive bacteria have simpler cell
walls -> large amounts of peptidoglycan
2. Gram-negative bacteria are more complex
-> less peptidoglycan + outer membrane
containing lipopolysaccharides (carbs
bonded to lipids)

Question 6

Gram –

Answer 6

o Violet/iodine stain -> colours/stains
the thin peptidoglycan layer
o Alcohol rinse removes outer
lipopolysaccharide layer + blue iodine
complex
o Safranin stains exposed peptidoglycan
layer pink

Question 7

Gram +

Answer 7

o Violet/iodine stain -> colours/stains
the thick peptidoglycan layer
o Alcohol can’t remove stain complex
o Safranin stains exposed
peptidoglycan layer -> however dark
blue stain masks red dye

Question 8

Medicinal/treatment implications:

Answer 8

• Staining can determine whether infection is
gram positive or gram negative and therefore
the type of treatment required

Question 9

medicinal/ treatment implications of Gram negative:

Answer 9

• Lipids of the lipopolysaccharides in the wall
are toxic, causing fever or shock
• Outer membrane helps protect it from body’s
defences
• Membrane also makes it difficult to detect
• More resistant to antibiotic than gram positive
due to membrane impeding entry of drugs
• Produces both endo and exotoxins
• Enter body through wound
Treatment à Antibiotic: streptomycin

Question 10

medicinal/ treatment implications of Gram positive

Answer 10

• Only produces exotoxins à proteins
excreted during lifespan
• Antibiotics such as penicillin prevents
peptidoglycan cross-linking
• This results in cell wall losing functionality

Question 11

Sources of antibiotics:

Answer 11

o Actinomycetes
o Bacillus
o Moulds

Question 12

Penicillin

Answer 12

inhibits cell wall synthesis by activating

‘transpeptidase’

Question 13

Resistance to penicillin

Answer 13

peniciltase

Question 14

peniciltase

Answer 14

bond to penicillin

molecule active sight

Question 15

Fluoroquinolones

Answer 15

inhibits DNA replication by bonding to
enzyme to prevent division
Resistance -> cell blocks bonding of enzyme

Question 16

Tetracycline

Answer 16

binds to ribosome, thereby blocking
protein synthesis
o Resistance -> bacteria pumps compound out of
cell

Question 17

1st layer -> Slime layer/capsule:

Answer 17

• Not always present
• Made of polysaccharides or proteins
• Dense -> capsule
• Not well organized -> slime layer
• Sticky to allow adherence to substrates or other
individuals in a colony
• Prevent dehydration or attack from host’s
immune system

Question 18

2nd layer -> outer polysaccharide layer/membrane

Answer 18

• Not always present

Question 19

3rd layer -> cell wall

Answer 19

• Gives bacterium shape
• Provides protection
• Prevents from bursting in hypotonic (low-salt)
environment
• Made from peptidoglycan (modified sugars &
polypeptides)
• Encloses bacterium and anchors molecules
extending from surface

Question 20

4th layer -> cell membrane

Answer 20

• Encloses cytoplasm

Question 21

Pili (pilum singular)

Answer 21

• Appendages that pull two cells together prior to

DNA transfer from one cell to another

Question 22

Plasmid

Answer 22

• Circular DNA

* Released into environment upon cell death

Question 23

DNA

Answer 23

• Less than eukaryote
• Not enclosed or compartmentalized by
membrane
• Circular chromosomes, located in
nucleoid

Question 24

Photosynthetic lamellae

Answer 24

• Not present always

* Can produce food

Question 25

Flagella (flagellum singular)

Answer 25

• Aids in motility of cell
• Differs entirely from flagella of eukaryotes
• Can be many or isolated on one end
• Move in response to stimulus

Question 26

Ribosomes

Answer 26

• Smaller than eukaryotes
• 2 sub units
• Aids in protein synthesis

Question 27

Ecological importance of Prokaryotes

Answer 27

• Nitrogen fixers
o Fix nitrogen into a form that can be used by other organisms for protein synthesis
• Nutrient recyclers + decomposers
o Recycle chemical elements between living and non-living components (unblock carbon,
nitrogen and other elements)

• Bioremediation
o Remove pollution and pollutants from environment (oil spills, metal rusting)
• Disease
o Maintain strength of gene pool, maintain population
• Natural antibiotics

Question 28

The endosymbiotic theory

Answer 28

• Theory stating that chloroplasts and mitochondria were integrated into eukaryotic cells
o Larger cell took in smaller cell either as prey or entered as a parasite
• Chloroplasts and mitochondria are known as à endosymbionts
• This indicates organelles in eukaryote descended from ancestral prokaryote that was engulfed by
another cell (eu or pro)
• The engulfed cell specialized into chloroplasts and mitochondria

Question 29

Evidence for endosymbiotic theory

Answer 29

1. Double membrane
   o Inner membrane’s enzymes + transport pathway is similar to prokaryotes
   o Outer membrane’s enzymes + transport pathway is similar to eukaryotes
2. Mitochondrial size similar to the size of prokaryotic organisms
3. Inner folding of mitochondria (christae) similar to inner folding of prokaryotes
4. Ribosomes in mitochondria are 70S, similar to ribosomes in prokaryotes
5. Circular structure of mitochondrial DNA similar to plasmids in prokaryotes
6. Mitochondria undergo binary fission as do prokaryotes