W2L2 - Archaea and Fossil Records

Question 1

Prokaryotic cells properties:

• Size
• DNA Structure (Compared Bacteria and Archea)

Answer 1

• Microscopic (1-10μm)
• DNA is single, circular chromosome (‘nucleoid’)
  
  • Domain Bacteria: No proteins attached to DNA
  • Domain Archaea: Proteins (‘histones’) attached to DNA

Question 2

Structure of the Prokaryotic Cell.

Answer 2

• Typically have a cell wall: Peptidoglycan
• Gram+ Bacteria: One surrounding membrane (Thicker wall)
• Gram- Bacteria: Two surrounding membranes (Thinner walls)

Question 3

Example of a gram-negative bacteria along with its layers

Answer 3

Cyanobacteria

• EL = External layer
• OM = outer membrane
• P = peptidoglycan wall
• CM = cytoplasmic membrane

Question 4

What is another name for prokaryotic flagellum? (Bacteria and Archea)

What are some properties?

• Composition (2)
• Action (3)
• Location (1)

Answer 4

Motility appendage: For movement

Composition:

• Long thin filament
• Composed of flagellin protein

Action:

• One of the only two rotating shaft designs in biology
• Corkscrew action
• 6,000 revolutions pm but drag from water reduces it to ~100 rpm

Location:

• Extracellular (not inside the cell membrane)

Question 5

How do prokaryotes divide? (2)

Steps (3)?

What is the speed of this

Answer 5

• “Binary Fission’
• Constricting ring pinches parent cell into two

1. Chromosome (circular) attached to plasma membrane
2. Chromosomal DNA replicates, and attachment points separate
3. The Cell divides and complete fission

About 20 minutes

Question 6

Properties of Archea (3).

• Environment
• Common features
• Diseases

Answer 6

Archaea specialize in extreme environments

Have features in common with eukaryotes (sister Domain)

No known pathogenic (disease) Archaea

Question 7

Archea inhabits extreme environment: First example

Answer 7

• Halophiles - Salt lovers
  
  • Saturating Salt Water
  • Pink Lake: WA

Question 8

Archea inhabits extreme environment: Second example

Answer 8

• Thermophiles - Heat lovers
  
  • Pyrolobus: >106 degrees
    
    • Reduce sulphur to sulphide for energy
      
      • Using this energy can fix CO2 into organic carbon
    • Don’t use oxygen or light

Question 9

Archea inhabits extreme environment: Third example

Answer 9

• Hadearchea
  
  • Discovered 3.2km underground
    
    • Survive at 80 degrees in constant darkness
  • Metabolise CO (Carbon monoxide) and H₂ (Hydrogen)

Question 10

Archea inhabits extreme environment: Fourth example

Answer 10

• Hydrothermal Vents - Black Smokers
  
  • Cracks in ocean floor (Water seeps in and contacts earth hot mantle)
  • Supercooked 400 degrees (Pressure stops water from boiling)
  • Erupts out of chimneys with lots of dissolved H₂S (Hydrogen Sulphide)

Question 11

Properties of tubeworms:

• Length (1)
• Composition (2)
• Metabolism (2)

Answer 11

• 2.4 m long
• No mouth, no stomach
• Full of symbiotic archaea
• Chemoautotrophs: Inorganic chemical reaction
  
  • Convert Sulphur to H2S
• Fastest growing invertebrates on earth

Question 12

What are Asgard prokaryotes? (2)

Why are they interesting? (1)

Answer 12

• Asgard prokaryotes are new members of Archea
  
  • Gene suggests cytoskeleton (give shape) like Eukarya
  • Might have endomembrane system like Eurkaya
• Recently grew Asgard in the lab and found they can swallow other cells

Discovery of Asgards suggest Eukaryotes are merely a branch within an Archea

Question 13

Did Prokaryotes or Eukaryotes exist first? (2)

How do we know? (2)

Answer 13

• Prokaryotes are at least 3.5 byo
• Eukaryotes are less than 2 byo (fossil evidence)
  
  • Prokaryotes preceded eukaryotes by about 1.5 billion years

Stromatolites - WA

• Stromatolites fossils tell us cyanobacteria existed 3.5 million years ago
  
  • Cyanobacteria - Photosynthetic Bacteria