Lecture 8

Question 1

What is the purpose of the cytoskeleton?

Answer 1

To help maintain cell shape and the positions of organelles.

Question 2

What are the three major components of the cytoskeleton?

Answer 2

• microtubules
• intermediate filaments
• microfilaments

Question 3

The cytoskeleton is highly _______ but still provides _______.

Answer 3

The cytoskeleton is highly DYNAMIC but still provides STABILITY.

Question 4

How are microtubules structured?

Answer 4

“Tubes”
• composed of tubulin subunits
• may radiate out from an
organizing centre (centrosome)

Question 5

What is the function of microtubules?

Answer 5

• resist compression
• provide cell motility:
- whole cell
-organelle movement

Question 6

What do cilia consist of?

Answer 6

Microtubules

Question 7

What motion do cilia make and what 2 functions does this provide?

Answer 7

A “rowing like” motion which can move the cell forward or move fluid past the cell when stationary.

Question 8

ATP-powered motor proteins can “walk” __________ or vesicles along ____________.

Answer 8

ATP-powered motor proteins can “walk” ORGANELLES or vesicles along MICROTUBULES.

Question 9

What is the structure of a microfilament?

Answer 9

"Ropes"
• double chain of actin subunits
• forms linear strands and threedimensional
networks (with
the aid of branching proteins)

Question 10

What are the main functions of microfilaments?

Answer 10

• resist tension
• cortical network under plasma membrane helps maintain cell shape
• provide a gel-like consistency to outer cytoplasm.

Question 11

What type of microfilaments support movement?

Answer 11

Linear actin microfilaments support movement. (eg. in muscle.)

Question 12

What is the structure of intermediate filaments?

Answer 12

“Cables”

Coiled, less dynamic than MT or MF. Made up of various proteins.

Question 13

What is the function of intermediate filaments?

Answer 13

• maintain cell shape
• anchor organelles
• nuclear lamina
• neuronal processes
    – neurofilaments

Question 14

How are cells joined together?

Answer 14

• cell junctions

* the extracellular matrix

Question 15

What are the 3 types of cell junctions?

Answer 15

• Tight junctions
• Desmosomes
• Gap junctions.

Question 16

What are the functions of tight junctions?

Answer 16

• keep neighboring cells tightly pressed together
• may form a continuous seal
• prevent movement of fluid
across cell layers

Question 17

What are the functions of desmosomes?

Answer 17

• anchoring junction
• attachments between sheets of cells e.g. muscle
• act like rivets (a “torn muscle” is a torn desmosome)

Question 18

What are the functions of gap junctions?

Answer 18

• a point of cytoplasmic contact between cells
• ions and molecules may pass from cell to cell
• allow rapid intercellular communication

Question 19

ECM composed of…

Answer 19

• material secreted by cells (fibroblasts)
• mainly glycoproteins (protein with carbohydrate)
• most abundant glycoprotein is collagen

Question 20

What makes up approx. 50% of the total body protein, and exists in the ECF?

Answer 20

Collagen fibres

Question 21

What kind of strength do collagen fibres have?

Answer 21

Great tensile strength.

Question 22

What causes scurvy?

Answer 22

A lack of vitamin C results in failure of collagen synthesis. Also, hydroxyproline amino acids cannot be formed and collagen fibres can’t link correctly.

Question 23

Collagen is embedded in a _______ ______

Answer 23

Proteoglycan matrix

Question 24

What is the function of proteoglycan matrix in the ECM?

Answer 24

• traps water in ECM

* resists compression and retains shape

Question 25

Some glycoproteins (_________) attach cells to ECM. Membrane proteins (_______) link ECM to cytoskeleton - a communication link from ECM to the cell interior

Answer 25

Some glycoproteins (FIBRONECTINS) attach cells to ECM. Membrane proteins (INTEGRINS) link ECM to cytoskeleton - a communication link from ECM to the cell interior.