Appendages Pili, Sexpilus and Flagella (in E. coli) Flashcards

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1
Q

What are fimbriae/pilli

A

thin filaments extending a few um from cell. located all over cell surface

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2
Q

What is the structure of pilli

A

multiple subunits of a protein arrange in helix. subunits held by hydrophobic force and non-covalent bonds. another adhesive protein located at tip

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3
Q

What is the fn of pilli

A

adhere to surfaces

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4
Q

Where are fimbriae subunits synthesized

A

synthesized in cytoplasm and exported into periplasm by Sec system

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5
Q

How do fimbriae subunits cross the OM

A

by using a chaperone usher system. in system subunits bound by periplasmic proteins called chaperones.chaperone deliver subunits to integral OM protein usher complex

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6
Q

What is the purpose of binding fimbriae subunits to chaperones

A

binding prevents subunits from assembling into fimbriae in periplasm.

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7
Q

What happens to pilli subunits at usher complex

A

subunits pass through a pore in the usher complex and self assemble into helical fibre that extends from surface of cell

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8
Q

Where does the growth of fimbriae helical fibre start from

A

from proximal end

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9
Q

What is the structure of the sexpillus

A

like pilli it is a filament composed of protein subunits. however larger in diameter and longer

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10
Q

What does the F (fertility) plasmid of E. coli encode

A

the genes for synthesis of sexpillus

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11
Q

What is the fn of sexpilli

A

used in conjugation to help overcome the electrostatic barrier between cells

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12
Q

When a flagella is peritrichous

A

multiple flagella all over cell surface. eg E. coli

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13
Q

Name the structural components of flagellum in E. coli

A

basal body, hook, filament and motor proteins. all made of proteins

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14
Q

Structure of the basal body of flagella

A

a hollow central rod running through four proteins rings

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15
Q

Describe the four protein rings of the basal body

A

L ring associated w/LPS. P ring associated w/peptidogylcan. MS ring is in PM, connected to rod. C ring attached to cytoplasmic side of MS ring to indirectly connect to rod

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16
Q

What is the C ring of basal body made up of

A

multiple copies of 3 Fli proteins

17
Q

Structure of hook component of flagella

A

short curved sleeve protruding from cell. connected to the rod of basal body and the filament

18
Q

Structure of the filament component of flagella

A

semi-rigid hollow helical filament composed of multiple subunits of a protein called flagellin

19
Q

What is associated with the MS ring

A

motor proteins MotA and MotB. MotB anchors MotAB complex to peptidoglycan

20
Q

Synthesis of the filament

A

Flagellin synthesized in cytoplasm. transferred to hollow core of the rod and hollow filament. new subunits are added to the distal end

21
Q

The motor of flagellum

A

the motor that turns the flagellum is composed of a rotor and a stator

22
Q

Structure of stator of flagella

A

stationary, composed of Mot proteins

23
Q

Fn of stator of motor of flagella

A

use PMF as source of nrg to turn rotor. proteins pass from periplasm to cytoplasm in channels of Mot proteins. produce a conformational change in Mot proteins, this turns rotor.

24
Q

Which part of the flagella turns and how

A

rotor is the C ring. turning of C ring turns the MS ring, the attach rod, hook and the filament. The L and P rings do not turn, they act as bushings

25
Q

When the filament turns CCW what peritrichous bacteria do

A

the hooks bend and filament forms a rotating bundle

26
Q

What is the default movement of filament

A

CCW

27
Q

What happens when the filament turns CW

A

cell tumbles, bundle is undone and cell stays in same area

28
Q

What affects the length of the runs

A

Hz in which the filament is switched from CCW to CW affects number of tumbles and number of random changes in direction. therefore affecting length