L26-Cytoskeletal microtubules, microfilaments and motility.

Question 1

what is the cytoskeleton?

Answer 1

they are structural proteins found in the cytoplasm used to maintain the cell shape and regulate intracellular movement whether of an organelle or a vesicle

Question 2

name the 3 types of cytoskeleton

Answer 2

1) microtubules
2) microfilaments
3) intermediate filaments

Question 3

describe the structure of the microtubules

Answer 3

they are long hollow and non branching tubes made form small subunits called tubulins they can be alpha or beta. they unite together to form a dimer.

Question 4

what does it mean that the microtubules are dynamic structures?

Answer 4

it means that they can change in length according to the cells requirement.

Question 5

what is a protofilament?

Answer 5

they are longitudinal arrangements of the dimers forming a long chain.

Question 6

state the number of protofilaments in every microtubules.

Answer 6

13 protofilaments

Question 7

what are the centrosomes?

Answer 7

microtubule organizing center, it’s a region close to the nucleus. it houses the centrioles and several hundred of the gamma tubular rings.

Question 8

what are the functions of the microtubules?

Answer 8

1- provide rigidity for the cell
2- regulate intracellular movement
3- establish intracellular compartments
4-during cell division microtubules are responsible for the formation of the mitotic spindle.

Question 9

what is colchicine and describe its action.

Answer 9

colchicine is a drug that bind with the tubulins of the leukocyte preventing the polymerization of microtubules. Therefore, interferes with the leukocytes movement and phagocytosis and further release of inflammatory substance

Question 10

what are microtubules associated proteins?

Answer 10

they are protein that help transport vesicle and organelles inside the cell and prevent the depolymerization of the microtubules.

Question 11

name the 2 types of microtubules associated proteins.

Answer 11

dynein and kinesine
dynein moves toward the negative end of the microtubule while kinesis moves towards the positive end.
this process is active and requires ATP.

Question 12

what are centrioles?

Answer 12

they ae small cylindrical structure composed of 27 microtubules arranged in triplets. they are a paired structure perpendicular to each other.

Question 13

what is the function of the centrioles?

Answer 13

1- they assist in the formation and organization of the microtubules.
2- formation of the spindle apparatus
3- they are basal bodies that guide the formation fo Celia and flagella (cell motility)

Question 14

Describe the structure of actin filament

Answer 14

its made up of 2 chains of actin globular proteins coiled around each other

Question 15

what are the functional forms of actin filament?

Answer 15

1 contractile bundels
2 gel like networks
3 bundles
4 focal points

Question 16

describe the function of contractile bundles?

Answer 16

the actin filaments here are arranged loosely and anti parallel to each other
1 they form cleavage furrow (contractile ring) during mitosis
2 movement of organelles and vesicles inside the cell
3 cellular activities such as exocytosis endocytosis and cellular extensions

Question 17

describe the function fo the gel like networks.

Answer 17

provide the structural foundation of the cell cortex

Question 18

describe the function of bundles of actin filament

Answer 18

its forms the core of microvilli (cell projections)

Question 19

describe the function of focal points

Answer 19

they are points of contact between the cell and extracellular matrix