lecture 13: eukaryotic structure

Question 1

Outside cell envelopes are pili, fimbriae, and flagella.

What are each used for?

Answer 1

Pili: attachment to surfaces and other cells

Fimbriae: DNA exchange (conjunction) and movement

Flagella: movement (swimming motility)

Question 2

Outside cell envelopes are pili, fimbriae, and flagella.

What are the differences between them?

Answer 2

Pili: short, numerous, helps in biofilm formation

Fimbriae: longer than fimbriae fewer in number

Flagella: long, whip-like structures for molitity

Question 3

Conjunction Pilis- What is it for?

Answer 3

Used for horizontal gene transfer (HGT)

Allows DNA exchange between bacteria, including antibiotic-resistance genes.

Question 4

Outside cell envelopes are pili, fimbriae, and flagella.

How does twitching motility work? ?

Answer 4

Uses Type IV pili to move across surfaces.

The pilus extends, attaches to a surface, then retracts, pulling the cell forward.

Question 5

Outside cell envelopes are pili, fimbriae, and flagella.

What are the key proteins known in twitching motility? What are they doing?

Answer 5

PilA: The pilus itself (extends out of the cell).

PilB: Works with PilC to extend PilA (uses ATP for energy).

PilT: Works with PilC to retract PilA (also ATP-driven).

PilC: Acts like a rotary motor, controlling extension and retraction.

Question 6

Flagella- What are the three pieces?

Answer 6

Filament – Made of flagellin, forms the whip-like structure.

Hook – Connects the filament to the basal body, transmits torque.

Basal Body – The motor that drives flagellar rotation.

Question 7

How is the flagella arragned differently in Gram + and Gram - cells?

Answer 7

Gram + : 2 rings (MS and C), attached directly to the cell, no outer membrane

Gram - : 4 rings (L, P, MS, C), anchored in both membranes (inner and outer), has outer membrane.

Question 8

How does the flagellum turn? What proteins are involved?

Answer 8

Driven by the proton motive force (PMF).

Mot proteins act as the motor, using proton flow to generate torque.

Fli proteins switch rotation between clockwise (CW) and counterclockwise (CCW).

Question 9

What rings fo Gram + and Gram - have? How is it powered?

Answer 9

Gram + : 2 rings
MS ring- Cytoplasmic
C ring: inside cytoplasm

Gram - : 4 rings
MS and C rings
L ring- anchors in outer membrane (LPS)
P ring- anchors in peptidoglycan