Chapter_3 Bacterial Cell Structure

Question 1

What characteristic shapes can bacteria assume? Describe the ways in which bacterial cells cluster together.

Answer 1

Can be in rods or cocci.
Can cluster in tetrads (4) or sarcinae (8)

Question 2

What advantages might the ability to form multicellular arrangements (e.g., clusters or chains) have that are not afforded single cells?

Answer 2

• More surface area
  Better protection

Question 3

List the functions of bacterial plasma membranes. Why must their plasma membranes carry out more functions than the plasma membranes of eukaryotic cells?

Answer 3

• Selectively permeable barrier
• Only allows certain things to enter and exit cell
• More functions than eukaryotic cells because doesn’t have membrane bound organelles

Question 4

Describe in detail the composition and structure of peptidoglycan. Why does peptidoglycan contain the unusual d-isomers of alanine and glutamic acid rather than the l-isomers observed in proteins?

Answer 4

• Mesh structure
• Alternating NAG and NAM sugars
• Alternating amino acids D and L
• D isomers better for crosslinking

Question 5

The cell walls of most members of the phyla Firmicutes and Actinobacteriota lack porins. Why is this the case?

Answer 5

• Gram positive so porins arent needed
• Small molecules can diffuse through thin plasma membrane
  No outer membrane to prevent diffusion

Question 6

What is the difference between a capsule and a slime layer? Why does the term glycocalyx usually encompass both?

Answer 6

• Capsule is a firm thin layer that is difficult to remove
• Slime layer is a thin layer that is easy to remove
• The glycocalyx encompass both because theyre made of polysaccharides and function for cell survival in harsh conditions

Question 7

Briefly describe the nature and function of the cytoplasm, and the regions and structures within it. How is the cytosol different from the cytoplasm?

Answer 7

• Cytoplasm separates organelles into different compartments
  Cytosol is fluid part of cytoplasm

Question 8

How do plasmids differ from chromosomes? What is an episome?

Answer 8

• Plasmids are circular non essential genes
• Plasmids replicate independently
  Episomes are plasmids that can integrate into chromosomes

Question 9

What are the functions of fimbriae and sex pili?

Answer 9

• Sex pili are responsible for bridging to other cells and initiating horizontal gene transfer
• Fimbriae are responsible for attaching to surfaces

Question 10

What terms are used to describe the different flagella distribution patterns observed among bacteria?

Answer 10

• Monotrichous = 1 flagellum
• Lophotrichous = cluster at both or one end
  Peritrichous = all around

Question 11

Describe the structure of the bacterial endospore using a labeled diagram

Answer 11

• Exosporium = thin covering of spore
• Spore coat = thick protein layers
• Cortex = thick peptidoglycan
• Inner membrane = protects dna
• Core = resistance to harsh conditions
  Dna = located within core