lecture 4 - prokaryotic cell structure Flashcards Preview

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Flashcards in lecture 4 - prokaryotic cell structure Deck (34):
1

cell

fundamental unit of life

2

cell characteristics

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

3

Bacterial cell structures

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

4

what is the cytoplasm

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

5

how do chromosomes fit into cell

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

6

characteristics of bacterial chromosomes

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

7

what s the cell envelope?

combination of cell membrane and wall
-protects cell and contains cytoplasm
-site of metabolic processes
-gram - bacteria have two

8

what are the functions of the cell membrane

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

9

gram + bacteria structure

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

10

Gram - bacteria structure

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

11

characteristics of lipopolysaccharides

-located on Outer layer of the outer membrane

Three domains:
-Lipid A (endotoxin - signals infection)
-Core polysaccharide
-O Antigen

12

what is the significants of the o antigen of lipopolysaccharides?

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

13

what does the cell wall do?

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"

14

what is a flagellum?

-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

15

how do bacteria move?

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

16

fimbriae

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

17

pili

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

18

glycocalyx slime layer

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

19

glycocalyx capsule

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

Ex) staphoccocus psnmonia has capsule to invade

20

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

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

-slimyness can determine pathogenicity

21

virulence

Ability of a microbe to cause disease in another organism

22

virulence factor

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

23

how do bacteria survive in hosts

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

24

how do microbes get into host cells?

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

Examples
Mucinase
Keratinase
Collagenase
Hyaluronidase

25

toxigenicity

ability to produce toxins
-weaken host, damage tissue

26

toxinoses

a variety of diseases caused by toxigenicity

27

toxemias

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

28

intoxications

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

29

what is the difference between exotoxins and endotoxins?

Eco - excreted by bacterium, target organs are damaged

endo: accidental ;not produced by bacteria. LPS (gram -)

30

how do antimicrobials work?

- 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

31

selectively toxic

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

32

where do antibiotics come from?

metabolic product of aerobic bacteria and fungi

-chemists alter structure of natural antibiotics to form new antibiotics

33

how do antibiotics target cells?

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

34

minimum inhibitory concentration (MIC)

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