Unit 1: Cell architecture (Cytoscaffolds)

Question 1

What is a cytoscaffold ?

Answer 1

A complex network of filamentous proteins extending throughout the cytoplasm

Question 2

What are the 3 types of filaments ?

Answer 2

• Microtubules
• Microfilaments
• Intermediate filaments

Question 3

What is the structure of an intermediate filament (4)?

Answer 3

• 8 stranded ropelike polymer
• More stable than other cytoskeletal fibres
• Do not bind to nucleotides (ATP or GTP)
• The strands twist together to form a hollow tube

Question 4

What do IF subunits combine to form ?

Answer 4

Tetramers that associate and twist to form rope

Question 5

What are the functions of intermediate filaments (2)?

Answer 5

• To provide mechanical strength
• Not contractile

Question 6

What are the 4 types of IFs ?

Answer 6

• Prekeratins
• Vimentin-like
• Neurofilaments
• Nuclear Lamins

Question 7

What are actin microfilaments required for ?

Answer 7

Cell migration and movement

Question 8

How are actin microfilaments formed ?

Answer 8

• Actin monomers aggregate together in a mechanism called nucleation
• This is concentration dependant

Question 9

What is tread milling ?

Answer 9

• The continuous addition of G-actin monomers at F-actin’s plus-end and the simultaneous removal from the minus-end
• How actin mfs move

Question 10

What are the 3 steps involved in tread milling ?

Answer 10

• Actin nucleation
• ATP cap formation
• Polymerisation

Question 11

The actin cytoskeleton can take forms of…..

Answer 11

• Parallel bundles of filaments
• Criss-crossed filaments that form a network

Question 12

How can the actin cytoskeleton be modified (3) ?

Answer 12

• Cross linking
• Cutting
• Binding of other proteins

Question 13

What are the 4 main elements of cell motility ?

Answer 13

• Gel sol transition with cytoplasm
• Lamellipodal extension
• Actin myosin interactions
• Focal contacts

Question 14

What is myosin involved in (3) ?

Answer 14

• Cell motility
• Transport of vesicles
• Moving membranes

Question 15

What are focal contacts ?

Answer 15

When cells make contact with their surroundings by means of their cellular feet

Question 16

When stationary what are these contacts known as ?

Answer 16

Focal adhesion plaques

Question 17

When moving what are these contacts known as ?

Answer 17

Focal contacts

Question 18

What are focal contacts and plaques sites for ?

Answer 18

Cell to cell signalling

Question 19

Are cytoplasmic microtubules unstable ?

Answer 19

Yes they are unstable and they display dynamic instability

Question 20

Which end of a cytoplasmic microtubule is more stable ?

Answer 20

The Positive end

Question 21

What is a dimer ?

Answer 21

2 monomers joined together

Question 22

What do defects in the Tau protein lead to ?

Answer 22

Neurodegenerative diseases

Question 23

What is the Anterograde direction ?

Answer 23

Transport from the cell body to the growing tip of the axon

Question 24

What is the Retrograde direction ?

Answer 24

Transport from the tip of the axon back to the cell body

Question 25

What is Anterograde transport powered by ?

Answer 25

Kinesin

Question 26

What does kinesin do ?

Answer 26

It hydrolyses ATP and is said to be a plus end directed motor

Question 27

What is retrograde transport powered by ?

Answer 27

Cytoplasmic dyein

Question 28

What does cytoplasmic dyein do ?

Answer 28

It hydrolyses ATP and is said to be a minus end directed motor

Question 29

What process are microtubules used in ?

Answer 29

Mitosis

Question 30

What is the axoneme ?

Answer 30

The central strand of cilia and flagella

Question 31

What do cilia and flagella do ?

Answer 31

They move substances over or around the cell (cilia) or move the cell itself (flagella)

Question 32

What is a molecular motor ?

Answer 32

Dyein arms that are responsible for generating the forces that cause the cilia to bend