Bacterial Cell Structure

Question 1

what is morphology

Answer 1

have to consider shape + arrangement

Question 2

describe coccus/cocci and state the 5 arrangements possible

Answer 2

• round & spherical

1. diplococci (two cells stuck together)
2. streptococci (chain-like arrangement)
3. tetrad (four cells stuck together)
4. sarcinae (eight cells stuck together)
5. staphylococci (grape-like clusters)

Question 3

describe bacillus/bacilli and state the 4 arrangements possible

Answer 3

• rod shaped cells

1. single (one bacillus)
2. diplobacilli (two bacillus stuck together)
3. streptobacilli (many bacilli stuck end to end)
4. coccobacillus (blobby rod shape)

Question 4

describe curved/spiral and state the 3 arrangements possible

Answer 4

• spiral

1. vibrio (curved rods)
2. spirillum (short, rigid spirals)
3. spirochete (long, flexible spirals)

Question 5

3 less common morphologies

Answer 5

1. filamentous bacteria
2. fruiting bodies (blobs on a stick)
3. biofilms

Question 6

pleomorphic

Answer 6

bacteria change morphology depending on enviro/cell state

Question 7

describe influence of cell size

Answer 7

smaller size = larger SA / volume ration

• easier for nutrients to move in and wastes to move out
• faster growth/ evolution

Question 8

what are the 4 structures shared by all bacteria

Answer 8

• cytoplasm
• ribosome
• plasma membrane
• nucleoid containing DNA

Question 9

what is the cell envelope

Answer 9

= plasma membrane and all layers external to it

• plasma membrane
• cell wall
• external layers

Question 10

what does the plasma membrane consist of?

Answer 10

• phospholipids
• hopanoids
• various proteins
• glycolipids
• oligosaccharides

Question 11

what do sterols/ hopanoids do in the plasma membrane and which are found in pro vs euk

Answer 11

maintain the fluidity and structure of the membrane

sterols = euk (cholesterol)
hopanoids = pro (bacteria)

Question 12

the plasma membrane regulates ……….

Answer 12

regulates transport in/ out of the cell

Question 13

passive diffusion

Answer 13

substances move across membrane with concentration gradient
- does NOT require energy or proteins

Question 14

facilitated diffusion

Answer 14

move with concentration gradient with help of integral membrane proteins
- NO atp needed

Question 15

active transport

Answer 15

moved against concentration gradient
- requires ATP

Question 16

what substances can travel via passive diffusion vs facilitated

Answer 16

passive = small, nonpolar, not charged
facilitated = large, polar, charged

Question 17

primary vs secondary active transport

Answer 17

primary = uses energy from ATP hydrolysis to move substances across membrane

secondary = uses energy from another molecule

• both require changes to integral proteins to provide a channel of travel

Question 18

group translocation

Answer 18

molecules are modified as they enter the cell

Question 19

what do cell walls do in bacteria

Answer 19

provide bacteria with structure and protection
-rigid
-porous
-peptidoglycan

Question 20

gram staining separates cell walls based on ______ content

Answer 20

peptidoglycan content

Question 21

gram positive vs gram negative vs atypical

Answer 21

gram positive = one membrane, thick peptidoglycan layer (purple)

gram negative = two membranes, thin peptidoglycan layer (pink)

atypical = neither structure

Question 22

overall charges of gram + & -
~ where do they get these charges from?

Answer 22

BOTH negative!

(+) from teichoic and lipoteichoic acids
(-) from LPS (lipopolysaccharide)

Question 23

gram + are really susceptible to _____ because…..

Answer 23

to penicillin as they have no outer membrane

Question 24

cell walls are essential to cell survival as they keep …..

Answer 24

keep from osmotic lysis in isotonic conditions !

Question 25

does having a cell wall protect a cell in hypertonic conditions?

Answer 25

no not fully

Question 26

atypical gram positive bacteria

Answer 26

mycobacterial cell walls - inner membrane, peptidoglycan, outer membrane - in outer membrane there is mycolic acid which holds the purple color

Question 27

atypical gram negative bacteria

Answer 27

do not retain purple color - inner and outer membrane with NO peptidoglycan layer - stains pink

Question 28

what does lysozyme do

Answer 28

breaks B1-4 linkages which destroys peptidoglycan (will not retain purple)

Question 29

what emerges from membranes and what do they do

Answer 29

EVs extracellular vesicles they carry cargo thru extracellular enviro to fuse with other cells

Question 30

how do EVs get thru the cell wall

Answer 30

osmotic pressure pushes out membrane through gaps/pores in peptidoglycan

Question 31

what differentiates EVs from cells

Answer 31

EVs = no full genome, cannot undergo metabolic reactions

Question 32

what would u expect in gram + EVs vs gram - EVs ?

Answer 32

+ = plasma membrane surrounding cytoplasm - = outer membrane budding out

Question 33

types of external layers

Answer 33

glycocalyx (sugar) coatings: - slime layers - capsules (bacteria) protein coatings: - S-layers (archaea)

Question 34

what are slime layers

Answer 34

- allows for attachment to surfaces and other cells (shared) - allows for motility - can live together in biofilms

Question 35

capsules

Answer 35

- only associated with cell that made it - no motility - can adhere to surfaces - protect cell from dehydration, phagocytosis

Question 36

capsules are ____ to both negative and simple stain so it will be _____ after

Answer 36

resistant to both stains and will be colorless after

Question 37

what are s-layers

Answer 37

present mostly archaea - made of proteins - provide structure - self assembles

Question 38

describe the cytoplasm

Answer 38

- very crowded - contains cytosol (liquid) & soluble molecules

Question 39

describe cytoskeleton

Answer 39

- some bacteria have similar structures to those of euk proteins tubulin homologues = FtsZ (cell devision) intermediate homologues = CreS (gives vibrio shape) actin homologues = MreB (give cell rod shape)

Question 40

which prokaryote has eukaryotic actin cytoskeleton proteins

Answer 40

archaeal cell Loki type bacteria

Question 41

intracytoplasmic membranes

Answer 41

not the same as membrane bound organelles - more SA = more ATP synthesis

Question 42

inclusions and the 4 types

Answer 42

used for storage 1. PHA/B granules = store hydrocarbons 2. phosphate globules = store components for making nucleic acids 3. sulfur globules = store H2S to be used in metabolism 4. gas vacuoles = allow to regulate buoyancy

Question 43

why would bacteria store items in inclusion bodies

Answer 43

- protecting inside from enviro - easier to keep track of stores - concentrated amount in one area

Question 44

ribosome difference in bacteria vs euk and why does this make them a good target for antibiotics

Answer 44

do the same job just bacteria are slightly smaller and 70S not 80s good as antibiotics would only be specific to and recognize bacteria not euk so wouldn’t harm human cells

Question 45

bacteria structure

Answer 45

circular genome - single double stranded

Question 46

plasmids

Answer 46

not part of chromosome - circular double stranded DNA - makes something transmissible

Question 47

what external structures are used for attachment and motility

Answer 47

attachment: - pili = attach cell to cell - fimbriae = attach cell to surface (short) motility: - flagella = allow cells to move around (long)

Question 48

mono,lopho and peritrichous flagella

Answer 48

monotrichous = single hairlike lopho = tuft of flagella perit = all angles covered by flagella

Question 49

how do bacteria decide when and how to move?

Answer 49

move in response to stimuli: - chemotaxis = moving toward/ away from chemical stimuli - phototaxis = moving toward/ away from light stimuli many use tumble and run movement (travel in random directions)

Question 50

describe endoscopes

Answer 50

formed by SOME gram + bacteria - soil bacteria - NOT a method of reproduction - cell is dormant in extreme conditions

Question 51

sporulation vs germination

Answer 51

sporulation = forming endospores is triggered by cell stress germination = reaches favourable conditions