CELS 191 Lecture 5

Question 1

what is the function of the cytoskeleton

Answer 1

maintaining the structure of the cell as well as the positions of the organelles

Question 2

how does the cytoskeleton allow the cell to rapidly change shape

Answer 2

the cytoskeleton rapidly disassembles and reassembles - it is highly dynamic but still provides stability

Question 3

what are the main components of the cytoskeleton

Answer 3

microtubules, microfilaments and intermediate filaments

Question 4

what is the composition of microtubules

Answer 4

tubulin subunits arranged in a spiral pattern

Question 5

what is the biggest of the cytoskeleton components

Answer 5

microtubules

Question 6

what is a centrosome

Answer 6

an organising centre from which microtubules radiate out from

Question 7

do microtubules resists compression or tension

Answer 7

compression - therefore they help maintain cell shape

Question 8

how do microtubules provide cell motility

Answer 8

cilia use a rowing like motion to move either the cell itself or the fluid outside the cell if the cell is fixed in place. flagella use a snake like motion to move the cell

Question 9

which component of the cytoskeleton provide motility within the cell

Answer 9

microtubules - ATP powered motor proteins can walk organelles along microtubules like a road

Question 10

what is the composition of microfilaments

Answer 10

a double chain of actin subunits that are twisted like a rope

Question 11

what is the smallest of the cytoskeleton components

Answer 11

microfilaments

Question 12

what are the two forms microfilaments can take

Answer 12

linear strands or 3d networks (using branching proteins)

Question 13

are microfilaments used to resist compression or tension

Answer 13

tension

Question 14

what is the cortical network

Answer 14

a network of microfilaments just under the plasma membrane helps make this region less fluid and thus maintains cell shape

Question 15

what do the interactions between the actin of microfilaments and motor proteins such as myosin support

Answer 15

cell movement

Question 16

what are intermediate filaments composed of

Answer 16

various proteins including: keratins in hair, lamins in the nucleus and neurofilaments in neurons - tightly coiled into ‘cables’

Question 17

which is the least dynamic component of the cytoskeleton

Answer 17

the intermediate filaments - this makes them relatively permanent cellular structures that are used for maintaining cell shape and anchoring organelles

Question 18

what is the only component of the cytoskeleton that remains after the cell has died

Answer 18

intermediate filaments - like in your hair and skin

Question 19

what are the three types of cell junctions

Answer 19

tight junctions
desmosomes
gap junctions

Question 20

what is a tight junction

Answer 20

a junction that hold neighbouring cells tightly pressed together - they may form a continuous seal around the cell

Question 21

what is the function of a tight junction

Answer 21

to stop thing slipping between the cells. they also present the movement of fluid across cell layers

Question 22

what is a desmosome and what is its function

Answer 22

an anchoring junction that is used to provide attachments between sheets of cells

Question 23

how are desmosomes connected

Answer 23

intermediate filaments

Question 24

what is a gap junction

Answer 24

a point of cytoplasmic contact between two cells

Question 25

what is the function of a gap junction

Answer 25

to allow ions and small molecules to pass from cell to cell - this allows of rapid intercellular communication

Question 26

does the composition of the ECM vary depending on the tissue type

Answer 26

yes

Question 27

what is the ECM composed of

Answer 27

material secreted by the cells

Question 28

how does the secretion of substances that make up the ECM occur

Answer 28

through constitutive exocytosis - a process that release materials from the inside to the outside of cells

Question 29

what type of proteins make up the majority of the ECM proteins

Answer 29

glycoproteins (proteins with added carbohydrates) - the most abundant of which is collagen fibres which have great tensile strength

Question 30

what are the collagen fibres of the ECM embedded in

Answer 30

a proteoglycan matrix

Question 31

what is a proteoglycan and what are their role in the ECM

Answer 31

a protein with extensive sugar additions that trap water within the ECM - water resist compression and thus helps retain tissue shape

Question 32

what are fibronectins and what is their function in the ECM

Answer 32

glycoproteins that attach the cells to the ECM

Question 33

what connects the ECM to the cytoskeleton and what is their function

Answer 33

membrane proteins - they provide a communication link fro the ECM to the cell interior