U1-KA5 - PROTEIN CONTROL OF CELL DIVISION - 1)remodelling of the cytoskeleton

Question 1

What is the cytoskeleton - which cells is it in

Answer 1

A network of protein fibres ep that extends through the cytoplasm in all eukaryotic cells

Question 2

Where is the cytoskeleton attached and what is its function

Answer 2

• the cytoskeleton is attached to membrane proteins and gives mechanical support and shape to the cell , acting as scaffolding to maintain its shape.

Question 3

The cytoskeleton constantly ______ down and __ _____

Answer 3

The cytoskeleton constantly breaks down and reforms

Question 4

What does the cytoskeleton consist of - where are these found

Answer 4

The cytoskeleton consist of different protein structures including microtubules - which are found in all eukaryotic cells

Question 5

What are microtubules

Answer 5

• microtubules are hollow straight cylinders composed of proteins called tubulin
• they radiate from the microtubule organising centre (MTOC) or centrosome
• they are polymers of a dimer made from soluble proteins a tubulin and b tubulin,
• the dimers are arranged to form microtubules and these have a diameter if 25nm.

Question 6

What does the formation and breakdown of micotubules involve

Answer 6

The formation and breakdown of microtubules involves polymerisation (growth of the microtubule) and depolymerisation (shrinkage of the microtubule ) of tubulin

Question 7

What is the function of microtubules

Answer 7

Microtubules control the movement of membrane bound organelles that are attached to them and the movement of chromosomes during cell division

Question 8

Where to microtubules originate / radiate from

Answer 8

• found in all eukaryotic cells , microtubules radiate from the microtubule organising centre (MTOC) or centrosome.
• in animal cell the centrioles form part of the centrosome and are involved in the organisation of the spindle fibres during cell division

Question 9

• Where is the centrosome (MCOT) found

- what does it contain and what is this

Answer 9

• the centrosome is found near the nucleus

- and it contains centrioles , which are the site of microtubule synthesis within the centrosome .

Question 10

Cell division requires the _________ of the cells microtubules/cytoskeleton

Answer 10

Cell division requires the remodelling of the cells microtubules/cytoskeleton
- microtubules play an important role in cell division as this process requires remodelling of the cytoskeleton

Question 11

Microtubule also form ______ ______

How?

Answer 11

Microtubule also form spindle fibres
- microtubule are disassembled to form the spindle fibres and the spindle fibres control the movement of chromosomes during mitotic and meotic divisions

Question 12

The centrosome is duplicated and then these two move to _________ ____of the cell.

Answer 12

The centrosome is duplicated and then these two move to opposite ends of the cell

Question 13

What are the three roles of microtubules during cell division

Answer 13

1) the aster or star shaped tuft of microtubules at each centrosome ensures that cell division apparatus is correctly located
2) some of the spindle microtubules consist of microtubules attached to kinetichore proteins at the centromeres at each chromatid
3) other microtubules in the spindle do not attach to microtubules from the opposite centrosome