Lecture 27: introduction to Prokaryotic cells

Question 1

the cell wall of bacteria is…

Answer 1

peptidoglycan

Question 2

function of Bacteria cell wall:

Answer 2

• rigid macromolecular layer that provides strength to cell

- protect cell from osmotic lysis and confers cell shape

Question 3

prokaryotes that lack cell walls are…

Answer 3

mycoplasmas

Question 4

what are mycoplasmas?

Answer 4

group of pathogenic bacteria

Question 5

peptidoglycan is in a…

Answer 5

mesh-like structure

Question 6

Transpeptidase is…

Answer 6

the enzyme that cross-links the peptidoglycan chains to form rigid cell walls

Question 7

the structure of peptidoglycan:

Answer 7

• NAG/NAM
• side chains amino acids
• cross bridge amino acids

Question 8

gram stain procedure produces:

Answer 8

• gram-negative bacteria in red

- gram positive bacteria in purple

Question 9

gram stain procedure:

step 1 -

Answer 9

application of crystal violet (purple dye)

Question 10

gram stain procedure:

step 2 -

Answer 10

application of iodine (mordant)

Question 11

gram stain procedure:

step 3 -

Answer 11

alcohol wash (decolorisation)

Question 12

gram stain procedure:

step 4 -

Answer 12

Application of safranin (counterstain)

Question 13

Structure of a gram-positive bacteria cell wall:

Answer 13

• cell wall (peptidoglycan layer)

- plasma membrane

Question 14

the peptidoglycan layer in gram-positive bacteria is…

Answer 14

thick

Question 15

thick peptidoglycan traps…

Answer 15

crystal violet, which masks the red safranin dye

Question 16

structure of a gram-negative bacteria cell wall:

Answer 16

• cell wall (outer membrane/peptidoglycan)

- plasma membrane

Question 17

the peptidoglycan layer in gram-negative bacteria is…

Answer 17

thin

Question 18

in the thin layer of peptidoglycan crystal violet is…

Answer 18

easily washed away, revealing the red safranin dye

Question 19

motile bacteria produce…

Answer 19

flagella

Question 20

flagella are long flexible…

Answer 20

appendage resembling “tails”

Question 21

flagella act like…

Answer 21

a propeller, cell rotates them to move through a liquid medium

Question 22

number and location of flagella on a cell…

Answer 22

can very

Question 23

3 Major sections of flagella:

Answer 23

• long filament
• hook
• basal body

Question 24

long filament structure of flagellum:

Answer 24

• extends into surrounding medium
• composed of subunits
  (protein = flagellin)

Question 25

Hook structure of flagellum:

Answer 25

- curved section connecting the filament to the cell surface

Question 26

basal body structure of flagellum:

Answer 26

- anchors flagellum into cell membrane

Question 27

how are flagellum anchored into the cell membrane:

Answer 27

by special disc-shaped structures called plates or rings

Question 28

tactical response moving in response to environment

Answer 28

chemotaxis

Question 29

positive chemotaxis:

Answer 29

bacteria move along concentration gradient towards a chemical attractant

Question 30

negative chemotaxis:

Answer 30

bacteria move away from a chemical repellent

Question 31

temporal gradients are:

Answer 31

change in chemical concentrations outside the cell over time

Question 32

Bacterial adherance factors:

Answer 32

glycocalyx - capsules - slime layers

Question 33

glycocalyx is a...

Answer 33

- gelatinous polysaccharide | - or polypeptide outer covering

Question 34

glycocalyx forms a...

Answer 34

sticky meshwork of fibres

Question 35

glycocalyx organised into a defined structure attached firmly to cell wall is...

Answer 35

capsule

Question 36

glycocalyx disorganised without cell shape, attached loosely to cell wall is...

Answer 36

slime layer

Question 37

glycocalyx capsules can serve numerous functions including:

Answer 37

- virulence factors - adhere to cell surfaces and structures - prevent cell from drying out (desiccation)

Question 38

virulence factors is:

Answer 38

protecting bacteria from phagocytosis and engulfment by immune cells

Question 39

example of capsule adherence:

Answer 39

to medical implants and catheters

Question 40

bacterial endospores are formed during...

Answer 40

unfavourable growth conditions

Question 41

bacterial endospores germinate under...

Answer 41

favourable conditions

Question 42

bacterial endospores protects cells from...

Answer 42

stress

Question 43

bacterial endospores are only present in...

Answer 43

some gram positive bacteria | - members of the genus bacillus

Question 44

endospores are...

Answer 44

highly differentiated cells

Question 45

endospores are resistant too:

Answer 45

- heat - harsh chemicals - antibiotics - disinfectants - radiation

Question 46

endospores can stay dormant...

Answer 46

for a very long time