Cytoskeleton

Question 1

What is the cytoskeleton?

Answer 1

Cytoskeleton—>network of fibres that extends throughout the cytoplasm
o Involved in maintaining and organizing structure of cell

Question 2

What is cytosol?

Answer 2

> Cytosol: The semi-fluid portion of the cytoplasm

Cytosol—> h2O and dissolved ions, proteins, carbohydrates, nucleic acids

Question 3

What are the roles of the cytoskeleton? (4)

Answer 3

• Mechanical support—> maintains shape
o Important in animal cells due to the lack of cell wall
• Provides anchorage for cell organelles
• Dynamic structure
o Can be disassembled, or de-polymerized, in one part of the cell and then reassembled in another part—> Changes the shape of the cell
• Involved in cell motility—> changes to cell location and movement of cell parts
o Requires interaction between cytoskeleton elements and motor proteins
o Above two work with the plasma membrane and cause cells to move along fibre networks outside of a cell
o Inside cells organelles and vesicles often use motor proteins to walk along tracks provided by the cytoskeleton to their destinations

Question 4

What are the three components of the cytoskeleton?

Answer 4

• Cytoskeleton consists of three components:

1. Microtubules—> the thickest of the three
2. Microfilaments—> the thinnest of the three
3. Intermediate filaments—> fall intermediate to the thickness of microtubules and microfilaments

Question 5

What is the cytoplasm?

Answer 5

Cytoplasm:

> made from cytosol and cell organelles embedded within the cell cytoplasm

Question 6

How is the cytosol separated?

Answer 6

> Cytosol is fundamentally separated from the organelles and their inner components as they are membrane-bound

Question 7

The contents of the cell are bounded by the ____ membrane.

Answer 7

plasma

Question 8

How does the cytoskeleton manipulate the cell membrane?

Answer 8

The cytoskeleton can also manipulate the cell membrane to form phagocytosis and hence form vacuoles from the invagination in the cell membrane engulfing a food particle or other.

Question 9

Define what the cytoskeleton is?

Answer 9

Cytoskeleton: a network of microtubules, microfilaments and intermediate filaments that extend throughout the cytoplasm and serve a variety of mechanical, transport, dynamic and signal functions.

Question 10

How are the cilia and flagella formed?

Answer 10

Cilia and flagella are formed fundamentally by sub-units made from the cytoplasm.

Question 11

What is the nuclear lamina (lines the inner surface of the nuclear membrane)? (2)

Answer 11

> a dense fibrillar network inside the nucleus of most cell nuclei.
made up of many intermediate filaments and membrane-associated proteins that all work collectively to provide nucleus structures and anchorage (General mechanical support)

Question 12

Microtubules
• Straight ____ rods
• 25nm in diameter and 200nm to 25um in length
• Are able to ______ move and reassemble

Answer 12

hollow

disassemble

Question 13

What is the composition of microtubules?

Answer 13

Globular proteins: alpha-tubulin and beta-tubulin

Question 14

What is the function of the microtubules? (3)

Answer 14

• Shape and support the cell
• Provide tracks along which organelles can move
• Cell motility

Question 15

Where do microtubules grow out from?

Answer 15

Microtubules grow out from the centrosome

Question 16

What are centrioles?

Answer 16

In the centrosome of the animal cells, there are a pair of centrioles
• Centriole is composed of 9 sets of triplet microtubules arranged in a ring

Question 17

What do centrioles do?

Answer 17

Centrioles help organize microtubule assembly

Question 18

What is the centrosome? (3)

Answer 18

• an organelle near the nucleus of a cell that contains the centrioles (in animal cells) and from which the spindle fibres develop in cell division.
• centrioles are found at right angles to each other; the centrosome is the microtubule origin site
• a set of microtubules triplets surround the inner cavity

Question 19

What are the functions of the cilia and flagella?

Answer 19

motility of cells

Question 20

Flagella are ____ structures and few in number, while cilia are ____ and numerous.

Answer 20

long

short

Question 21

What is the structure of cilia and flagella? (2)

Answer 21

• Structure—> central core of two microtubules is surrounded by 9 doublets of microtubules
(9+2 pattern)
• Doublets have attached motor proteins, the dynein arms, that help bend the flagella

Question 22

Size of microfilaments: solid rods approximately ___ in diameter.

Answer 22

7nm

Question 23

What is the composition of microfilaments?

Answer 23

Composition—>built from two intertwined strands of actin, a globular protein

Question 24

What is the function of microfilaments? (3)

Answer 24

• Aid in the contraction of muscles
• Microfilaments are attached to myosin
• Contraction of the cell results in actin and myosin microfilaments sliding past one another, this shortens the cell—>see muscle contraction (m line, z line, ADP, ATP, myosin, actin, myosin head)

Question 25

How does muscle contraction work? (4)

Answer 25

> actin filaments (microfilaments) are connected to myosin filaments containing myosin heads
The myosin heads/ projections walk and causes the contraction of actin filaments parallel to the myosin movement
This causes muscle cell contractions
Muscle contraction involves many muscle cell contractions simultaneously and in sync

Question 26

What is the size of intermediate filaments?

Answer 26

8-12nm in diameter

Question 27

True or false

Intermediate filaments are more permanent structures than microtubules and microfilaments

Answer 27

True

Question 28

What is the composition of intermediate filaments? (2)

Answer 28

• Several proteins like keratins

* Fibrous proteins coiled

Question 29

What is the function of intermediate filaments?

Answer 29

• Providing structure to the cell, and anchoring of organelles within the cell