Cell Structure and Function in Bacteria and Archaea Flashcards
What are the major cell morphologies?
• Coccus (plural, cocci): spherical or ovoid
• Rod or bacillus: cylindrical shape
• Spiral:
o Spirillum: rigid
o Spirochete: corkscrew-like, flexible, varying shape; tightly coiled
What are minor cell morphologies?
• Budding and appendaged: possess extensions of their cells as long tubes or stalks (stalk can be detachable)
• Filamentous: long, thin cells or chains of cells
• Pleomorphic: bacterial population with highly variable shapes
o They lack cell wall
What is cell morphology?
Morphology means cell shape. Shapes are key identifying elements for bacteria.
How can cell morphology be used to predict other cell properties?
Cell morphology is a poor predictor of a cell’s other properties (physiology, ecology, phylogeny etc.)
However, morphology might optimize certain fitness criteria (e.g. nutrient uptake, swimming motility in viscous environments or near surfaces, gliding motility etc.)
What is MreB? What is its role?
• MreB is a protein that confers cell shape
• Different variants are responsible for varying shapes
• The protein’s network within the cell resembles the eukaryotic internal cytoskeleton
o MreB is homologous to actin
• Spheric (coccal) cells have no MreB
What explains the size of coccus bacteria?
• Coccus don’t exceed 2μm
o They can only receive nutrients and excrete waste by simple diffusion
o This size minimizes the simple diffusion surface
Explain the relationship between cell size and surface area-to-volume ratio. What does this accomplish?
Small size increases the surface area-to-volume ratio
Creates more efficient movement of nutrients and wastes between the cell interior and environment
Greater nutrient exchange per unit of cell volume, leading to faster growth
Faster metabolic rate, leading to faster growth
metabolic rate= 1/〖cell size〗^2
No need for cytoplasmic stream
No internal cytoskeleton network
How can metabolic rate be measured?
metabolic rate= 1/〖cell size〗^2
Name the major prokaryotic cell structures.
- Cytoplasmic membrane
- Cell wall
- Ribosomes
- Storage granules
- Nucleoid
- Plasmid
What are the major functions of the cytoplasmic membrane?
1) Highly selective permeability membrane
a. Can selectively concentrate nutrients within cell
b. Can selectively eliminate toxic by-products
2) Anchor site for proteins
a. Transport proteins
b. Chemotoxic proteins: these sense the environment
c. Proteins for energy generation
3) Generate and use H+ gradient for energy
Where is the cell wall located?
Outside the cytoplasmic membrane
What are the functions of the cell wall?
1) Provides rigidity to shape of cells
2) Protection against osmotic lysis
a. Counteracts osmotic pressure
How do bacterial and arcaheal ribosomes differ?
They have different ribosomal RNA (rRNA) and different ribosomal proteins
What are the storage granules main components and what do they store?
1) Glycogen: glucose storage
2) PHA (poly-β-hydroxyl alkanoate): substituted carboxylic acids
a. Carbon storage (similar to fatty acids)
3) Polyphosphate
Describe the content of the nucleoid.
Genomic DNA
• Single circular molecule (chromosome)
• Haploid
• Contains all genes required for survival and growth of cell
