the microbial cell

Question 1

what are the different shapes of bacteria and their associated names

Answer 1

1) spherical= coccus
2) rodshaped= bacillus
3) spiral shaped = spirillum

Question 2

what is the functions of the prokaryotic cell envelope

Answer 2

• maintains shape
• provides protection
• prevents bursting or rupture in hypotonic environments

Question 3

outline the structure of the prokaryotic cell envelope

Answer 3

• cell membrane
• cell wall
• outer membrane which is only present in gram negative bacteria

Question 4

why is the cell membrane not enough to protect prokaryotes

Answer 4

the lipid nature makes the cell membrane vulnerable to chemicals so often they surround the cell membrane with tough cell wall

Question 5

outline the structure or formation of the cell wall

Answer 5

• made up of murein
• glycan chains made up of N-acetylglucosamine and N-acetyl muramic acid connected by beta 1-4 glycosylic bonds
• these form crosslinked with other chance via small peptides

Question 6

outline what a gram positive cell is

Answer 6

the cell membrane is surrounded by a thick cell wall made of murein
absence of an outer membrane
- teichoic acids provide rigidity and help bacteria adhere to surfaces

Question 7

what do beta lactam antibiotics do

Answer 7

inhibit peptidoglycan/murein synthesis

Question 8

outline the process of b-lactams acting on bacteria

Answer 8

1) bind to and inactivate the enzyme which assembles the murein chains and bonds the peptides of the layers together
2) with no active enzyme the cell wall cant be remodelled as it grows
3) the cell wall weakens causing internal osmotic pressure to cause the cell to burst

Question 9

outline the structure of a gram negative cell

Answer 9

a thin layer of murein as well as the presence of an outer membrane made up of lipopolysaccharides

Question 10

what is the lipopolysaccarhide membrane made up of

Answer 10

1) one glycolipid
2) a polysaccharide core
3) a long carbohydrate chain

Question 11

what is an O antigen

Answer 11

an antigen made up of varying numbers of repeating units which is very immunogenic and redners addtional protection from certain antibiotics

Question 12

what are porins

Answer 12

protein channels in the membranes of gram negative bacteria which mediates the diffusion of hydrophilic compounds

Question 13

what is the periplasm

Answer 13

a gel like space between the cell membrane and the outer membrane where the murein layer is found

Question 14

what does the periplasm contain

Answer 14

1) degradative enzymes which break down molecules so they can be transported across inner membrane
2) proteins
3) beta lactamases which protect the cells by inactivating antibiotics

Question 15

what are mycolic acids

Answer 15

alternatives in some bacteria to cell walls- a wax of 60-90 long fatty acids which orientate themselves into lipid bilayers

Question 16

what are acid fast bacteria

Answer 16

bacteria with an outer membrane made of mycolic acids

Question 17

outline the characteristics of acid fast bacteria

Answer 17

more resistant to harsh chemicals and desiccation as the membrane is very hydrophobic

Question 18

outline the process of acid fast staining for identification

Answer 18

1) stain with carbol fuchsin in presence of heat
2) was with a mixture of acid and alcohol to decolourise all but acid fast cells
3) counter stain with methylene blue to show non acid-fast cells

Question 19

what are mycoplasmas

Answer 19

bacteira which do no have a cell wall only a cell membrane and have sterols in the membranes to make them more rigid

Question 20

what are capsules/slime layers

Answer 20

a layer made up of high-molecular polysaccharides or polymers of amino acids
when attached to the cell= capsule
when loose = slime layer

Question 21

outline the structure of a flagellum

Answer 21

1) a long helical filament
2) a connecting hook
3) a basal body equipped with a rotor to turn flagellum

Question 22

outline the structure of the filament of the flilament

Answer 22

a helical rigid hollow composed of a protein called flagellin
very antigenic

Question 23

outline the structure of the hook of the filament

Answer 23

a joint betwen the filament of the basal body and filament made of a hook protien

Question 24

outline the structure of the basal body of the filament

Answer 24

a rod attached with rings which anchors the structure to the cell envelope allowing the rod to roate

Question 25

what are pili

Answer 25

hair structures which allow the cell to attache to hosts and surfaces to transfer proteins and move

Question 26

what proteins make up pili

Answer 26

pilins

Question 27

outline pili twitching mobility

Answer 27

1) pili extend and retract by adding or removing the pilin protein to the base of the pili
2) pili touches surface and he adhesins in the tip adhere
3) the pilus depolymerizes the base shortening the pilus dragging it forward