Chapter 4

Question 1

Describe the shape, arrangement, and size of archaeal cells.

Answer 1

• Like bacterial cells, they exhibit a variety of shapes including cocci and rods
• Typical rods are 1 to 5 um long
• Typical cooci are 1 to 3 um long
• Some known ones are 0.2 to 0.5 um long
• Highly diverse

Question 2

What is the difference in the plasma membrane of bacteria and archaea?

Answer 2

• Archaea plasma membranes contain glycerol diethers that form lipid bilayers
• Bacteria have ester-linked phospholipids and hopanoids form a lipid bilayer
• Archaea also have monolayer membranes that function like bilayers
• Lipids lack fatty acids, they have isoprenes instead

Question 3

What is the difference in the cell wall between bacteria and archaea?

Answer 3

• Bacteria cell walls made up of peptidoglycan

- Archaea cell walls LACK peptidoglycan

Question 4

Are the 16S rRNA genes similar in bacteria and Archaea?

Answer 4

No, they are different. They have different nucleotide structures, which is the main basis for bacteria and archaea being their own taxa

Question 5

How does the different lipids in Archaeal cell membranes affect the membrane?

Answer 5

• They contain hydrocarbons derived from isoprene units, which are branched. This affects the way the lipids pack together, which in turn affects the fluidity of the membrane and its permeability.
• This is extremely important for extremophilic archaea for which membrane fluidity and permeability could be compromised by extreme conditions
• Hydrocarbons are then attached to glycerol by ether links, which are more resistant to chemical attack and heat

Question 6

What are the two major types of archaeal lipids?

Answer 6

Glycerol diethers (lipid bilayers) and Diglycerol tetraethers (lipid monolayers)

Question 7

What is the most common type of archaeal cell wall?

Answer 7

• An S-Layer composed of either glycoprotein or protein
• The layer may be as thick as 20 to 40 nm
• Some only have an S- layer while some have the S-layer plus additional layers

Question 8

What is pseudomurein?

Answer 8

• May be outermost layer of cell wall
• Peptidoglycan like molecule
• Differs from peptidoglycan in that it has L-amino acids instead of D-amino acids in its cross links, N-acetyltalosaminuronic acid instead of N-acetylmuramic acid, beta 1 to 3 glycosidic bonds instead of 1 to 4
• Lysozymes and penicillin have no affect on cell walls like they do in bacterial cell walls

Question 9

How do Archaeal cells uptake nutrients?

Answer 9

• Use many of the same mechanisms exhibited by bacteria such as active transport and facilitated diffusion
• No group translocation mechanisms

Question 10

How do archaeal ribosomes differ from bacterial ribosomes?

Answer 10

• They have more proteins (68 rather than 55)