Cytoskeleton, Lecture 7

Question 1

What is the cytoskeleton?

Answer 1

The cytoskeleton is a structure that maintains cell shape, internal organization, provides mechanical support for division, and supports movement.

Question 2

What are general functions of filaments in the cytoskeleton?

Answer 2

Filaments allow cells to maintain and change shape, provide coordinated movement, support intracellular transport, and maintain organelle distribution.

Question 3

What functions or processes are microtubules involved in?

Answer 3

Microtubules are involved in mitosis, cell motility, intracellular transport, and maintenance of cell shape.

Question 4

What filament in the cytoskeleton is the largest?

Answer 4

Microtubules are the filaments in the cytoskeleton with the largest diameter.

Question 5

What monomers are microtubules made of?

Answer 5

Microtubules are made of the protein subunit, tubulin.

Question 6

Filaments in the cytoskeleton can be described as ‘dynamic’. What does this mean?

Answer 6

Filaments are described as ‘dynamic’ because they can grow or shrink rapidly in length through assembly and disassembly.

Question 7

Describe what it means by the ‘plus’ and ‘minus’ ends of filaments in the cytoskeleton.

Answer 7

The plus end generally has more assembly and a higher rate of growth, while the minus end has slower growth and more depolymerisation.

Question 8

What is catastrophe?

Answer 8

Catastrophe is the switch from growth to shrinking.

Question 9

Describe where assembly and disassembly occurs in the microtubule structure.

Answer 9

Assembly occurs at the positive end via polymerisation of tubulin subunits, while the minus end is anchored to the microtubule organising centre (MTOC).

Question 10

What are MTOCs (microtubule organising centres)?

Answer 10

MTOCs are structures that anchor microtubules; in eukaryotic dividing cells, the centrosome is a primary MTOC.

Question 11

What is dynamic instability?

Answer 11

Dynamic instability is the ability of microtubules to grow or shrink rapidly in response to a cell’s needs.

Question 12

What is dynamic instability dependent on in microtubules?

Answer 12

Dynamic instability is dependent on tubulin concentration and microtubule associated proteins.

Question 13

What structures do microtubules make up?

Answer 13

Microtubules make up motile structures such as cilia and flagella, and are found in centrioles.

Question 14

What are motor proteins?

Answer 14

Motor proteins are proteins that walk along a microtubule while transporting a substance, powered by the hydrolysis of ATP.

Question 15

In what direction of the microtubule do motor proteins work towards?

Answer 15

Kinesin motor proteins move towards the plus end of the microtubule.

Question 16

In what direction of the microtubule do dynactin motor proteins work towards?

Answer 16

Dynactin proteins move towards the minus end of the microtubule.

Question 17

What is a type of microfilament found in skeletal muscle cells?

Answer 17

Actin microfilament is present in skeletal muscle cells and functions in the sliding filament model for muscle contraction.

Question 18

What is the smallest type of filament in the cytoskeleton, in terms of diameter?

Answer 18

Microfilaments are the smallest filament in terms of diameter.

Question 19

What sub-units make up actin filaments?

Answer 19

Actin filaments are made up of G-actin subunits that polymerise to form F-actin, which twist together to form a helix shape.

Question 20

What other functions do actin carry out, other than playing a part in the sliding filament model?

Answer 20

Actin supports microvilli structure, forms a cleavage furrow during cell division, and is involved in cytoplasmic contraction.

Question 21

What is treadmilling?

Answer 21

Treadmilling is the process where assembly and disassembly occur at the same rate, maintaining a constant length of actin filaments.

Question 22

What are some functions of microfilaments?

Answer 22

Microfilaments determine cell surface shape, control cell locomotion, and serve as tracks for motor proteins in transport and contraction.

Question 23

Name a motor protein that works along microfilaments.

Answer 23

Myosin is a motor protein that travels along microfilaments towards the plus end.

Question 24

Name some types of intermediate filaments and where they are found.

Answer 24

Keratin is found in skin and hair cells, while myosin is found in skeletal muscle cells.

Question 25

What are some functions of intermediate filaments?

Answer 25

Intermediate filaments resist stress and deformation, hold organelles in position, and facilitate network communication.

Question 26

What is assembly?

Answer 26

Assembly is the addition of subunits to the plus end of filaments in the cytoskeleton.