8. Plasma membrane ,Capsule and Flagelli

Question 1

what’s cytoplasmic membrane

Answer 1

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

Question 2

what does cellular intake of small molecules depend on

Answer 2

external concentration

Question 3

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

Answer 3

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

Question 4

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

Answer 4

-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

Question 5

what important proteins are in cell membrane

Answer 5

carboxypeptidases and transpeptidases, forming peptidic bonds between peptidoglycan monomers

Question 6

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

Answer 6

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

Question 7

How does cell membrane take part in cell division process

Answer 7

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

Question 8

What is anchorage of proteins used for

Answer 8

Transport, energy production (oxidative phosphorylation), chemotaxis

Question 9

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

Answer 9

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

Question 10

What % of dry weight does cell membrane account for

Answer 10

10%-26%

Question 11

How is cell membrane organized

Answer 11

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

Question 12

What do both leaflets of membrane contain

Answer 12

Phospholipids

Question 13

What are phospholipids

Answer 13

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

Question 14

What’s characteristic for bacterial phospholipids

Answer 14

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

Question 15

Can phospholipids have variable substitutions in their polar head

Answer 15

Yes

Question 16

What’s characteristic for Gram- bacteria and phospholipids

Answer 16

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

Question 17

Compare Archaea and other’s cell membrane

Answer 17

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

Question 18

What characteristic do species with higher resistance have in their phospholipids

Answer 18

Two leaflets are linked, like in hyperthermophilic archaea

Question 19

What chemical, similar to sterol, is in bacteria

Answer 19

Hopanoids

Question 19

What does cytoplasmic membrane has a lot of

Answer 19

Saturated fatty acids(without double bonds)

Question 20

What is the difference with lipids between eukaryotes and bacteria

Answer 20

Bacteria doesn’t have sterol, exception is Mycoplasms

Question 21

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

Answer 21

Proteins

Question 22

What’s function of proteins in cell membrane

Answer 22

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

Question 23

What do permeases do

Answer 23

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

Question 24

What polymeric extracellular substances are present in the plasma membrane

Answer 24

-**glycocalyx** -**capsule** -**slime layer**

Question 25

What's the structure of polymeric extracellular substances

Answer 25

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

Question 26

What's function of glycocalyx

Answer 26

-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)

Question 27

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

Answer 27

*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

Question 28

What's capsule made out of

Answer 28

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.

Question 29

Is capsule essential and permanent structure and why

Answer 29

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

Question 30

Are polysaccharides forming the capsule hydrated and why

Answer 30

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

Question 31

What's capsule anchored to

Answer 31

Phospholipids or lipid A of the outer membrane

Question 32

What's slime layer

Answer 32

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

Question 33

Name some bacterial appendages

Answer 33

-Flagelli -Pili/Fimbriae

Question 34

What are flagelli

Answer 34

*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

Question 35

What kind of organizations can flegelli have

Answer 35

*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)

Question 36

What's the structure of flagelli

Answer 36

1) Filament 2) Hook 3) Basal body

Question 37

What's flagellar filament

Answer 37

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

Question 38

What's flagellar hook

Answer 38

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

Question 39

Is basal body different in Gram + and - bacteria

Answer 39

Yes

Question 40

What's basal body made of

Answer 40

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

Question 41

How is rotation generated in the basal body

Answer 41

By *Mot proteins* interacting with Fli proteins on the basal ring

Question 42

How is energy for rotating provided

Answer 42

By proton-motive force

Question 43

What about flagellum or Archaea

Answer 43

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

Question 44

Can unicellular eukaryotes have flagellum

Answer 44

Yes, but it has different structure

Question 45

What's bacterial swimming motion based on

Answer 45

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

Question 46

What's chemotaxis

Answer 46

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

Question 47

What other aimed bacterial movement can exist except chemotaxis

Answer 47

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

Question 48

What chemotaxis movement results into

Answer 48

directional neat translation

Question 49

What's chemotaxis regulated by

Answer 49

Flagellum motion

Question 50

What's MCPs

Answer 50

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

Question 51

What are other forms of bacterial motility?

Answer 51

swimming, spirochete motility, twitching, gliding

Question 52

What are spirochetes

Answer 52

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

Question 53

What's the function and motion of axial filament

Answer 53

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