lecture 4 - prokaryotic cell structure

Question 1

cell

Answer 1

fundamental unit of life

Question 2

cell characteristics

Answer 2

• spherical or cylindrical
• cytoplasmic membrane
• chromosomes (DNA)
• ribosomes for protein synthesis
• reproduce to form progeny cells
• obtain energy from environment

Question 3

Bacterial cell structures

Answer 3

all: cell membrane, cytoplasm, ribosomes, chromosomes
most: cell wall, surface coating (glycocalyx)
some: flagella, pili, fimbriae, capsules, slime layers, endospores

Question 4

what is the cytoplasm

Answer 4

Gelatinous solution (proteins)
Site for many metabolic activities
70%-80% water
Also contains large cell masses (ex: chromatin, ribosomes, granules)

Question 5

how do chromosomes fit into cell

Answer 5

lots of DNA is packed into cell, some are “lysed” to let DNA escape out of cell so it isn’t so cramped
-it is compacted by twisting (supercoiling) and protein binding

Question 6

characteristics of bacterial chromosomes

Answer 6

-single circular DNA strand located in the nucleotide (dense area of cell)

Question 7

what s the cell envelope?

Answer 7

combination of cell membrane and wall

• protects cell and contains cytoplasm
• site of metabolic processes
• gram - bacteria have two

Question 8

what are the functions of the cell membrane

Answer 8

• Energy reactions (ATP synthesis; proton and ion gradients)
• Regulates transport (selectively permeable membrane)
• Secretion

Question 9

gram + bacteria structure

Answer 9

2layers
Cell membrane
Thick cell wall (peptidoglycan)

-Cell wall anchored to membrane and covered with sugar on the outside used to repelle water, and things you don’t want, helps with infection

Question 10

Gram - bacteria structure

Answer 10

3 layers

1. outter membrane
   - -Long sugar filaments extend from outside (lipopolysaccharides)
   - inside is phospholipid layer which is anchored to peptidoglycan layer by lipoproteins
   - has porin proteins for access into cell
   - only small molecules to penetrate
   - extra layer of protection that substances have to get through
2. Thin cell wall (peptidoglycan)
3. Cell membrane

Question 11

characteristics of lipopolysaccharides

Answer 11

-located on Outer layer of the outer membrane

Three domains:

• Lipid A (endotoxin - signals infection)
• Core polysaccharide
• O Antigen

Question 12

what is the significants of the o antigen of lipopolysaccharides?

Answer 12

O antigen is the dominant antigen of Gram negative cells

V. cholerae O139
Caused epidemic in india in 90’s

O1 pandemic strain
E. coli O157

Question 13

what does the cell wall do?

Answer 13

determines shape, provides structural support
-made of 1 cell peptidoglycan = sugar (glycan) and protein (peptide)

-when antibiotics target this cells pop because no structure or support - “lysis”

Question 14

what is a flagellum?

Answer 14

• propeller for swimming
• driven by proton motive force
• +/- chemotaxis and phototaxis
• rotates rapidly
• three parts: Filament (tail), hook (where it attaches), and basal body (motor)
• vary in number and arrangement

Question 15

how do bacteria move?

Answer 15

Flagellum can only propel when rotating counterclockwise
Tumbles (stops)
Runs (moves)

Speed:
Spin rate
Spin duration

“steering” is accomplished by running more than tumbling when it gets close to attraction

Question 16

fimbriae

Answer 16

used for attachment

• allow to stick to things
• smaller than flagellum - short pills
• can be 1000/ cell

-stick to one another to form bridge in HGT conjugation

Question 17

pili

Answer 17

used for:

• attachment
• genetic exchange (plasmids)
• Motility (slow spiderman webgrab/ swing)
• Very important for infection and interactions with host

Question 18

glycocalyx slime layer

Answer 18

a loose shield that protects some bacteria from loss of water and nutrients

Question 19

glycocalyx capsule

Answer 19

when the glycocalyx is bound more tightly to the cell and is denser and thicker

Ex) staphoccocus psnmonia has capsule to invade

Question 20

in general what types of bacteria usually have glycocalyx and why?

Answer 20

• pathogenic bacteria
• Capsule protects bacteria against phagocytosis by immune cells

-slimyness can determine pathogenicity

Question 21

virulence

Answer 21

Ability of a microbe to cause disease in another organism

Question 22

virulence factor

Answer 22

Microbial components that contribute to the ability to cause disease in a susceptible host

• what is virulence factor for one organism may be a colonization factor for another (good vs bad bacteria)
  example: fili, fimbriae, capsules, flagella are used by commensals and pathogens

Question 23

how do bacteria survive in hosts

Answer 23

-Blocked phagocytic response: Bacteria escape and persist ***CAPSULES
Immune system can subsequently overreact when body can’t clear the bacteria

Question 24

how do microbes get into host cells?

Answer 24

Exoenzymes: break down and inflict damage on tissues OR dissolve host defence barriers

Examples
Mucinase
Keratinase
Collagenase
Hyaluronidase

Question 25

toxigenicity

Answer 25

ability to produce toxins | -weaken host, damage tissue

Question 26

toxinoses

Answer 26

a variety of diseases caused by toxigenicity

Question 27

toxemias

Answer 27

toxinoses in which the toxin is spread by the blood from the site of infection (ex: tetanus and diphtheria)

Question 28

intoxications

Answer 28

toxinoses caused by ingestion of toxins (botulism) - Not infected - Toxins can be very species specific in target

Question 29

what is the difference between exotoxins and endotoxins?

Answer 29

Eco - excreted by bacterium, target organs are damaged endo: accidental ;not produced by bacteria. LPS (gram -)

Question 30

how do antimicrobials work?

Answer 30

- drugs Disrupt the cell processes or structures of bacteria, fungi, and protozoa / stop viral replication -interfere with the function of enzymes required to synthesize and assemble macromolecules or, destroy structures already formed in the cell

Question 31

selectively toxic

Answer 31

**GOAL** | drugs kill or inhibit microbial cells without damaging host tissues

Question 32

where do antibiotics come from?

Answer 32

metabolic product of aerobic bacteria and fungi -chemists alter structure of natural antibiotics to form new antibiotics

Question 33

how do antibiotics target cells?

Answer 33

``` cell wall inhibitors cell membrane inhibitors metabolic inhibitors DNA replication inhibitors RNA Polymerase inhibitors protein synthesis inhibitors ```

Question 34

minimum inhibitory concentration (MIC)

Answer 34

The lowest concentration of antibiotic at which a species can’t grow -when antibiotics are used at incorrect MIC levels that bacteria isn't killed results in evolution of resistance