Anatomy of Prok and Euk Cells

Question 1

Briefly describe the functions of the flagella of a bacterial cell.

Answer 1

Flagella allow bacteria to move toward or away from stimuli (taxis)
Flagella rotate to “run” or “tumble”
Flagella proteins are H antigens and distinguish among serovars (e.g., Escherichia coli O157:H7)

Question 2

Briefly describe the size and arrangement of bacterial cells.

Answer 2

• Average size: 0.2 to 2.0 μmeter diameter × 2 to 8 μmeter length
• Most bacteria are monomorphic (single shape)
• A few are pleomorphic (many shapes)

Question 3

Briefly describe the possible arrangements of bacterial cells.

Answer 3

pairs: diplo-
clusters: staphylo-
chains: strepto-
fours: tetrads
cube/eights: sarcinae

Question 4

Describe major features of the prokaryotic cell.

Answer 4

Prokaryote
* One circular chromosome, not in a membrane
* No histones
* No organelles
* Bacteria: peptidoglycan cell walls
* Archaea: pseudomurein cell walls
* Divides by binary fission

Question 5

Briefly describe the physical form of the flagella of a bacterial cell.

Answer 5

Three parts:
Filament: outermost region
Hook: attaches to the filament
Basal body: consists of rod and pairs of rings; anchors flagellum to the cell wall and membrane

Question 6

Briefly describe the model describing the cytoplasmic membrane.

Answer 6

Fluid mosaic model
Membrane is as viscous as olive oil
Proteins move freely for various functions
Phospholipids rotate and move laterally
Self-sealing

Question 7

Describe major features of the eukaryotic cell.

Answer 7

Eukaryote
* Paired chromosomes, in nuclear membrane
* Histones
* Organelles
* Polysaccharide cell walls, when present
* Divides by mitosis

Question 8

Briefly describe gram-positive cell walls.

Answer 8

thick peptidoglycan
has teichoic acids

Question 9

Briefly describe the additional features of the gram-negative cell wall.

Answer 9

Protect from phagocytes, complement, and antibiotics
Made of lipopolysaccharide (L P S)
O polysaccharide functions as antigen (e.g.,
E. coli O157:H7)
Lipid A is an endotoxin embedded in the top layer
Porins (proteins) form channels through membrane

Question 10

Briefly describe the cytoplasmic membrane.

Answer 10

Phospholipid bilayer that encloses the cytoplasm
Peripheral proteins on the membrane surface
Integral and transmembrane proteins penetrate the membrane

Question 11

Briefly describe the cell walls of mycoplasmas.

Answer 11

atypical.
lack of cell walls
sterols in plasma membrane

Question 12

Briefly describe axial filaments.

Answer 12

Also called endoflagella
Found in spirochetes
Anchored at one end of a cell
Rotation causes cell to move like a corkscrew

Question 13

Briefly describe acid-fast cell walls.

Answer 13

Atypical cell wall
similar to gram-positive
waxy lipid (mycolic acid) bound to peptidoglycan
stain with carbolfuchisin
examples: mycobacterium, nocardia

Question 14

Briefly describe fimbriae.

Answer 14

Hairlike appendages that allow for attachment.

Question 15

Briefly describe the flagella of a bacterial cell.

Answer 15

Filamentous appendages external of the cell
Propel bacteria
Made of protein flagellin

Question 16

Briefly describe the glycocalyx.

Answer 16

• External to the cell wall
• Viscous and gelatinous
• Made of polysaccharide and/or polypeptide

Two types:
* Capsule: neatly organized and firmly attached
* Slime layer: unorganized and loose

Question 17

Briefly describe the effects of lysozyme on cell walls.

Answer 17

Lysozyme hydrolyzes bonds in peptidoglycan.

Question 18

Briefly describe effects of penicillin on the cell wall.

Answer 18

Penicillin inhibits peptide bridges in peptidoglycan.

Question 19

Briefly describe the functions of the cytoplasmic membrane.

Answer 19

The plasma membrane’s selective permeability allows the passage of some molecules, but not others
Contain enzymes for ATP production
Some membranes have photosynthetic pigments on foldings called chromatophores

Question 20

Briefly describe the possible shapes of bacterial cells.

Answer 20

bacillus - rod-like
coccus - spherical
spiral (vibrio, spirillum, spirochete)
star-shaped
rectangular

Question 21

Define Plasmids.

Answer 21

extrachromosomal genetic elements; carry non-crucial genes (antibiotic resistance, production of toxins)

Question 22

Contrast some things between gram-positive and gram-negative cell walls.

Answer 22

Gram Positive
2 rings in basal body of flagella
Produce exotoxins
High susceptibility to penicillin
Disrupted by lysozyme

Gram Negative
4 rings in basal body of flagella
Produce endotoxins and exotoxins
Low susceptibility to penicillin

Question 23

Briefly describe the purpose of the cell wall in bacteria.

Answer 23

Prevents osmotic lysis and protects the cell membrane.
Contributes to pathogenicity.

Question 24

Define Bacterial chromosome

Answer 24

circular thread of DNA that contains the cell’s genetic information

Question 25

Contrast flagella and cilia.

Answer 25

Projections used for locomotion or moving substances along the cell surface
Flagella-long projections; few in number
Cilia-short projections; numerous
Both consist of microtubules made of the protein tubulin
Microtubules are organized as 9 pairs in a ring, plus 2 microtubules in the center (9 + 2 array)
Allow flagella to move in a wavelike manner

Question 26

List and describe some inclusions.

Answer 26

Metachromatic granules (volutin)-phosphate reserves
Polysaccharide granules-energy reserves
Lipid inclusions-energy reserves
Sulfur granules-energy reserves
Carboxysomes-RuBis C O enzyme for CO2 fixation during photosynthesis
Gas vacuoles-protein-covered cylinders that maintain buoyancy
Magnetosomes-iron oxide inclusions; destroy H2O2

Question 27

Briefly describe endospores, sporulation, and germination.

Answer 27

Resting cells; produced when nutrients are depleted
Resistant to desiccation, heat, chemicals, and radiation
Produced by Bacillus and Clostridium
Sporulation: endospore formation
Germination: endospore returns to vegetative state

Question 28

Briefly describe the membranes of gram-negative cell walls.

Answer 28

Periplasm between the outer membrane and the plasma membrane contains peptidoglycan

Outer membrane made of polysaccharides, lipoproteins, and phospholipids

Question 29

Briefly describe how the glycocalyx contributes to virulence.

Answer 29

Contribute to virulence
* Capsules prevent phagocytosis
* Extracellular polymeric substance helps form biofilms

Question 30

Briefly describe gram-negative cell walls.

Answer 30

thin peptidoglycan
has outer membrane
has periplasmic space
Porins (proteins) form channels through membrane

Question 31

What are L forms?

Answer 31

L forms are wall-less cells that swell into irregular shapes.

Question 32

Briefly describe pili.

Answer 32

Involved in motility (gliding, twitching).
Conjugation pili involved in DNA transfer between cells.

Question 33

Briefly describe the composition of bacterial cell walls.

Answer 33

Peptidoglycan
Polymer of a repeating disaccharide in rows:
N-acetylglucosamine( N A G)
N-acetylmuramicacid (N A M)
Rows are linked by polypeptides

Question 34

Briefly describe teichoic acids.

Answer 34

Found in gram-positive cell walls.
Lipoteichoic acid links cell wall to plasma membrane
Wall teichoic acid links the peptidoglycan
Carry a negative charge
Regulate movement of cations
Polysaccharides and teichoic acids provide antigenic specificity

Question 35

Briefly describe the archaella of motile archaeal cells.

Answer 35

Archaeal motility structure
Made of glycoproteins archaellins
Anchored to the cell
Archaella (singular: archlaellum) rotate like flagella

Question 36

Briefly describe the cell walls of archaea.

Answer 36

atypical.
wall-less, or
walls of pseudomurein
(and lack NAM, D-amino acids)