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Microbiology > 8. Plasma membrane ,Capsule and Flagelli > Flashcards

8. Plasma membrane ,Capsule and Flagelli Flashcards

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1
Q

what’s cytoplasmic membrane

A

Cytoplasmic membrane-selective osmotic barrier, encasing the cytoplasm contains. Allows the passive diffusion of small substances(H20,O2,CO2, simple sugars and some liposoluble substances

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2
Q

what does cellular intake of small molecules depend on

A

external concentration

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3
Q

why can’t ions and non-ionic larger molecules use external concentration and how do they go around it

A

Because they have very slow diffusion through the membrane. Active transport system is required and specialized systems for protein secretion

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4
Q

what are some other functions of plasma membrane (aside of being osmotic barrier)

A

-Production of energy (enzymes catalyzing chemical reaction, ex: ATP production)
-Biosynthesis processes(ex: wall synthesis, replication)
-Takes part in cell division processes
-Anchorage of proteins
-Energy storage

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5
Q

what important proteins are in cell membrane

A

carboxypeptidases and transpeptidases, forming peptidic bonds between peptidoglycan monomers

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6
Q

what are some basic units of a cell wall that are formed at cytoplasmic level and how are they transported

A

teichoic acids, LPS ; Transferred to polymerization sites on the membrane

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7
Q

How does cell membrane take part in cell division process

A

Provides docking site for the replicating DNA and, by growing, determines the positions of the two newly synthesized chromosomes in the daughter cells

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8
Q

What is anchorage of proteins used for

A

Transport, energy production (oxidative phosphorylation), chemotaxis

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9
Q

What is the ration of components in bacterial plasma membrane and compare it to the eukaryotic cell

A

Bacterial cell membrane has 30%-40% of lipids and 60%-70% of proteins
Ratio is opposite in eukaryotic cell

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10
Q

What % of dry weight does cell membrane account for

A

10%-26%

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11
Q

How is cell membrane organized

A

Organization resembles fluid mosaic
It has:
* phospholipidic double layer
* globular proteins partially or completely immerged in the double layer (intrinsic or extrinsic respectively)
* lipids interacting with intrinsic proteins: lipo-proteic complexes

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12
Q

What do both leaflets of membrane contain

A

Phospholipids

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13
Q

What are phospholipids

A

Phospholipids- amphipathic molecules with an hydrophilic head (phosphate group) and two fatty acid tails( hydrophobic)

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14
Q

What’s characteristic for bacterial phospholipids

A

They are species-specific with differences between Gram+ and Gram-

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15
Q

Can phospholipids have variable substitutions in their polar head

A

Yes

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16
Q

What’s characteristic for Gram- bacteria and phospholipids

A

Gram - bacteria have phospholipids in inner leaflet of the outer membrane

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17
Q

Compare Archaea and other’s cell membrane

A

Archaea’s phospholipids have ether bonds(instead of ester) and uses glycerol-1-phosphate instead of glycerol-3-phosphate. It’s side chains are made of isoprene instead of fatty acids

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18
Q

What characteristic do species with higher resistance have in their phospholipids

A

Two leaflets are linked, like in hyperthermophilic archaea

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19
Q

What chemical, similar to sterol, is in bacteria

A

Hopanoids

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19
Q

What does cytoplasmic membrane has a lot of

A

Saturated fatty acids(without double bonds)

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20
Q

What is the difference with lipids between eukaryotes and bacteria

A

Bacteria doesn’t have sterol, exception is Mycoplasms

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21
Q

What is the main component of the cell membrane (that aren’t phospholipids)

A

Proteins

22
Q

What’s function of proteins in cell membrane

A

*structural stability
*Anchorage for :
-flagellum rotating apparate
-ATPase subunit
-chromosome
-chemotaxis proteins
*Complex enzymatic systems
*Transport proteins (specific permeases)

23
Q

What do permeases do

A

They take part in passive transport (facilitated diffusion) taking substance from higher concentration to the lower)

24
Q

What polymeric extracellular substances are present in the plasma membrane

A

-glycocalyx
-capsule
-slime layer

25
Q

What’s the structure of polymeric extracellular substances

A

Layers of homopolymers or heteropolymers of monosaccharides like hexose, hyaluronic acid and aminosugars

26
Q

What’s function of glycocalyx

A

-physiological wellness of the cell
-adhesion and aggregation in response to nutrient shortage, protection from phages, resistance to antibiotics
-protection from phagocytes
-reserve of carbohydrates
-antigenic specificity(typing)

27
Q

What’s capsule of cell membrane and what is its fucntion

A

Capsule- continuous, rigid, well defined structure, strongly adherent to cell envelope
It’s the material secreted by the cell wall and stays close to cell and provides protective lining
It has influence on antibiotic sensitivity ( absorbs drugs, reducing its binding to molecular targets ) and genetic exchange

28
Q

What’s capsule made out of

A

Polysaccharides (dextrane, destrine, levane, cellulose and often hyaluronic acids)
Every capsule contains only 1 type of polysaccharide. It’s made of repeated oligosaccharidic units with glycosidic bonds.

29
Q

Is capsule essential and permanent structure and why

A

No; its presence is influenced by the composition of the growth medium ( pathogenic bacteria can have it in vivo but loose it in vitro)

30
Q

Are polysaccharides forming the capsule hydrated and why

A

Yes;
-regulate the access of ions and molecules to cell envelope
-retain nutrients for bacterial growth
-prevent dehydration

31
Q

What’s capsule anchored to

A

Phospholipids or lipid A of the outer membrane

32
Q

What’s slime layer

A

Amorphous and non-uniform mass, loosely adherent to cell envelope

33
Q

Name some bacterial appendages

A

-Flagelli
-Pili/Fimbriae

34
Q

What are flagelli

A

Flagelli-propulsion organs(rotation motion); They are rigid proteic filaments with helical shape and are attached to the plasma membrane
Rotation can be bi-directional

35
Q

What kind of organizations can flegelli have

A

*polar, monotrichous (one at the end/one side)
*polar, lohotrichous (more at one side)
*polar, amphitrichous( one at both sides)
*peritrichous(many at both sides)

36
Q

What’s the structure of flagelli

A

1) Filament
2) Hook
3) Basal body

37
Q

What’s flagellar filament

A

polymer of protein Flagellin organized in hexagonal cylindrical structure forming an inner cavity. AA composition is species-specific

38
Q

What’s flagellar hook

A

Links the filament(propeller) with basal body(engine). It’s made of several units of protein FlgE

39
Q

Is basal body different in Gram + and - bacteria

A

Yes

40
Q

What’s basal body made of

A

Proteic rings are attached to membranes and peptidoglycan and are free to rotate. Proteic rod connects all rings and transfers rotation to the hook and filament

41
Q

How is rotation generated in the basal body

A

By Mot proteins interacting with Fli proteins on the basal ring

42
Q

How is energy for rotating provided

A

By proton-motive force

43
Q

What about flagellum or Archaea

A

They use different proteins for filament and are thinner. They rotate more slowly and as a consequence Archaea swim more slow than bacteria

44
Q

Can unicellular eukaryotes have flagellum

A

Yes, but it has different structure

45
Q

What’s bacterial swimming motion based on

A

On 2 actions:
-Run- flagellum spinning counterclockwise
-Tumble-flagellum spinning clockwise

46
Q

What’s chemotaxis

A

Movement aimed towards, or away from, a chemical source of stimulation

47
Q

What other aimed bacterial movement can exist except chemotaxis

A

Anything stimulated by some source, like: light(phototaxis), oxygen(aerotaxis), pressure(barotaxis), magnetic field(magnetotaxis)…

48
Q

What chemotaxis movement results into

A

directional neat translation

49
Q

What’s chemotaxis regulated by

A

Flagellum motion

50
Q

What’s MCPs

A

Methyl-accepting chemotaxis proteins(MCPs)- have pivotal role in signal transduction, acting like sensors sending information about concentration of chemoattractants to flagellar engine

51
Q

What are other forms of bacterial motility?

A

swimming, spirochete motility, twitching, gliding

52
Q

What are spirochetes

A

Helical-shaped bacteria that has two or more endoflagella forming the axial filament anchored to both cell poles(in the periplasm)

53
Q

What’s the function and motion of axial filament

A

Functionally similar to flagellum. Contraction-extension motion along axial filament produces rotation
It allows spirochetes to move through very viscous fluids or even crawl on solid surfaces

Microbiology (20 decks)

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