Prokaryotic External Structure and Function

Question 1

Prokaryote Characteristics (5)

Answer 1

• Circular chromosome
• No histones; archaea have histone-like proteins
• No organelles
• Peptidoglycan (murein) cell walls in bacteria; pseudomurein cell walls in archaea
• Divide by binary fission

Question 2

Eukaryote Characteristics (5)

Answer 2

• Paired chromosomes in nuclear membrane
• Histones
• Organelles
• Polysaccharide cell walls (when present)
• Divide by mitosis

Question 3

Bacillus

Answer 3

Rod shaped

Question 4

Coccus

Answer 4

Sphere shaped

Question 5

Spirillum

Answer 5

Spiral shaped

Question 6

Spirochaete

Answer 6

Corkscrew shaped

Question 7

Glycocalyx

Answer 7

Capsule: organized polysaccharide, difficult to remove, firmly attached to cell wall

Slime: disorganized polysaccharide, easy to remove, loosely attached to cell wall

Question 8

Peptidoglycan

Answer 8

Polymer of disaccharide made up of N-acetylglucosamine (NAG) with a B-1,4 linkage to N-acetylmuramic acid (NAM)

Question 9

Gram-Positive Cell Wall

Answer 9

Peptidoglycan linked by polypeptides and supported by techoic acid

Question 10

Gram-Negative Cell Wall

Answer 10

Peptidoglycan linked by polypeptides with an outer LPS layer; contains a periplasmic space and outer membrane to confer protection

Question 11

LPS

Answer 11

Lipopolysaccharide; Consists of Lipid A, a core polysaccharide, and a variable o-polysaccharide antigen; confers negative charge and repels hydrophobics

Question 12

Gram Positive (9)

Answer 12

• Thick peptidoglycan
• Abundant techoic acids
• No periplasmic space
• Limited LPS
• Low lipid content
• Resistant to mechanical stress
• Better in dry conditions
• Highly susceptible to lysozymes
• Penicillin sensitive

Question 13

Gram Negative (10)

Answer 13

• Thin peptidoglycan
• No techoic acids
• Periplasmic space
• Outer membrane
• Abundant LPS
• High lipid content
• Susceptible to mechanical stress
• Excel in host intestines
• Low susceptibility to lysozyme
• Low susceptibility to penicillin

Question 14

Bacteria Example without Peptidoglycan

Answer 14

Planctomycetes; protects it from certain DNA damaging metabolites

Question 15

Mycoplasmas Cell Wall

Answer 15

No cell wall; have sterols in plasma membrane

Question 16

Archaea Cell Wall

Answer 16

Lack cell wall or have walls made of pseudomurein (lacks NAM and D-amino acids)

Question 17

Different Taxis

Answer 17

• Aerotaxis (oxygen)
• Phototaxis (photon intensity)
• Chemotaxis (chemical concentration)

-Positive if towards a stimulus and negative if away from a stimulus

Question 18

Flagella Arrangements

Answer 18

• Peritrichous (all over cell)
• Monotrichous (one on one end)
• Lophotrichous (multiple on one end)
• Amphitrichous (one on each end)

Question 19

Flagellar Motion

Answer 19

Move like a rotor; can be reversible or unidirectional

Question 20

Flagellar Structure in Gram Negative

Answer 20

Filament of flagellin connects to hook which passes through the outer membrane via the L ring; the rod then passes through the peptidoglycan layer through the P ring and the plasma membrane through the MS ring, which terminates at the C ring; motor proteins surrounding the MS and C rings generate motion

Question 21

Fimbriae and Pili

Answer 21

• Made of self-assembling flagellin-like proteins
• More numerous and shorter than flagella
• Fewer pili than fimbriae
• Pili are for gene transfer and surface attachment (twitching motility, i.e. dragging)