Topic 3 -Cell Structure

Question 1

Cell structure of prokaryotic cell (compare & contrast)

Answer 1

No organelles
Reproduces by binary fission
Ribosome smaller than 70S
Peptidoglycan walls if Bacteria
Pseudomurein walls if Archaea
No histone proteins associated w/ chromosomes
One circular chromosome not in a membrane
No nucleus; have nucleoid

Question 2

Cell structure of eukaryotic cell (compare & contrast)

Answer 2

Has organelles
Reproduces via mitosis/meiosis
Ribosomes larger than 80S
No peptidoglycan 
polysaccheride (cellulose) walls if plant
Chitin walls if fungi
Have histone proteins associated w/ chromosomes
paired chromosomes in nuclear membrane
Have a nucleus & nucleolus

Question 3

What is monomorphic? What is pleomorphic?

Answer 3

mono- one shape

pleo -many shaped

Question 4

Identify the 3 basic shapes of Bacteria & describe

Answer 4

1. Bacillus -rod shaped
2. Coccus -spherical
3. Spiral -vibrio, spirillum, spirochete (look at lecture notes)

Question 5

Identify & describe the different arrangements of bacteria

Answer 5

Pairs: diplococci, diplobacilli
Clusters: staphylococci
Chains: streptococci, streptobacilli

Tetrads: 4’s
Sarcinae: 8’s

Question 6

Describe glycocalyx and its importance

Answer 6

general term describing extracellular material secreted by EUKARYOTES and PROKARYOTES.

Prokaryotes -used for producing biofilms (+ & -) e.g. plaque, shower scum, biofilm on medical implants

Eukaryotes -important for self recognition

Question 7

Describe the structure of prokaryotic flagellum

Answer 7

rotates
outside cell wall
made of chains of protein (flagellin)
attached to protein hook & anchored to wall/membrane by basal body

Question 8

Name & describe the different bacteria flagella arrangements

Answer 8

Peritrichous -around (surrounding)
Atrichous -without
Monotrichous -one
Amphitrichous -both (either end)
Lophotrichous -tuft

Question 9

A bit about axial filaments?

Answer 9

aka endoflagella
in spirochetes
anchored at one end of a cell
rotation causes movement

Question 10

Describe pili and fimbriae

Answer 10

pili -tube like structure for sex (transfer of plasmids b/w bacteria), composed of protein pilin.
fimbriae -used to stick bacteria to each other and to cells they’re invading (important in infection).
See lecture notes for good picture!

Question 11

What is chemotaxis and phototaxis?

Answer 11

chemo -chemical
photo -light
taxis -movement

movement toward or away from a chemical or light stimulus

Question 12

differentiate prokaryotic & eukaryotic flagella

Answer 12

pro flagella rotate, euk flagella beat

pro flagella composed of flagellin protein, euk composed of microtubules

Question 13

Cell walls prevent…?

Answer 13

osmotic lysis =>rupturing of the cell

Question 14

what is peptidoglycan made of?

Answer 14

it is a polymer of disaccheride.
N-acetylglucosamine (NAG)
N-acetylmuramic acid (NAM)

Question 15

A gram + stain retains what? Is more susceptible to?

Answer 15

crystal violet stain in peptidoglycan wall.

More susceptible to penicillin=>blocks synthesis of pepto=>cells lyse

Question 16

A gram - stain does not?

Answer 16

take up crystal violet dye (outer membrane blocks). Takes up counter stain safranin

Question 17

A gram + cell wall has?

Answer 17

a thick layer of peptidoglycan, no outer membrane (1 membrane layer), teichoic acids

Question 18

A gram - cell wall has?

Answer 18

a thin layer of peptidoglycan, protected by an outer membrane (2 membrane layers), periplasmic space

Question 19

Describe endosymbiotic theory (you must know the basics)

Answer 19

prokaryotes were engulfed by an ancient eukaryote. Mitochondria then evolved from aerobic endosymbionts, chloroplasts then evolved from photosynthetic endosymbionts, inside the host eukaryote.
Mito & Chloro have similar bacterial features (binary fission, own circular chromosomes, ribosomes, membrane size & thickness).