lecture 6 - cell shape regulation

Question 1

How is the cytoskeleton dynamic?

Answer 1

The components of the cytoskeleton are cosntantly assembling and disassembling to rapidly change the shape of the cell.

Question 2

What are the three components of the cytoskeleton that provide structure?

Answer 2

Microtubules, Microfilaments, Intermediate filaments

Question 3

What are microtubules made up of?

Answer 3

Tubulin subunits (dimers) in a twisted helix tube.

Question 4

What organelle do microtubules sometimes radiate out from?

Answer 4

Centrosomes

Question 5

What are centrosomes?

Answer 5

An organising centre, that is sometimes surrounded by microtubules, e.g. during the formation of the mitotic spindle

Question 6

What type cytoskeleton component best resists compression?

Answer 6

microtubules

Question 7

What structures create cell motility?

Answer 7

Flagella and cilia

Question 8

What are the cytoplasmic components of flagella and cilia?

Answer 8

Microtubules

Question 9

What is the role of cilia in a fixed cell?

Answer 9

The cilia beat back and forth, moving fluid/mucous past.

Question 10

How do the microtubules aid in organelle motility?

Answer 10

ATP powered motor proteins are able to attach to vesicles/other organelles and walk along microtubules to their targets.

Question 11

What is the structure of microfilaments?

Answer 11

Double chains of actin subunits that twist around each other.

Question 12

Actin is the component of what cytoplasmic structural component?

Answer 12

Microfilaments

Question 13

What structures can microfilaments form?

Answer 13

linear strands and 3D networks

Question 14

What is required to allow microfilaments to branch?

Answer 14

branching proteins

Question 15

How do microfilaments make the cell rigid?

Answer 15

They form a cortical network which replaces fluid in the cytoplasm, stiffening the cell.

Question 16

How do microfilaments aid in cell movement?

Answer 16

Actin in the microfilaments interacts with motor proteins to facilitate movement.

Question 17

What interaction leads to muscle contraction?

Answer 17

Actin-myosin interactions.

Question 18

What do Actin-Myosin interactions allow?

Answer 18

Muscle contraction, amoeboid movement, cytoplasmic streaming (in plants).

Question 19

What are two common proteins that make up intermediate filaments?

Answer 19

Keratin, Lamin

Question 20

How are intermediate filaments structured?

Answer 20

proteins are supercoiled into tight ‘cables’

Question 21

What is the least dynamic cytoplasm tubule/filament?

Answer 21

Intermediate filaments.

Question 22

What aids in maintaining structure in dead cells, such as hair and skin?

Answer 22

Intermediate filaments.

Question 23

What are the 3 major cell junction types?

Answer 23

Tight junctions, desmosomes, gap junctions

Question 24

What are tight junctions?

Answer 24

Junctions that press neighbouring cells close together, creating a continuous seal that prevents the movement of fluid between layers of cells.

Question 25

What are desmosomes?

Answer 25

Anchoring cell junctions that attach cells in sheets.

Question 26

What form of cell junctions are prevelant in muscle tissue?

Answer 26

Desmosomes

Question 27

What connects desmosomes into the cell?

Answer 27

Intermediate filaments

Question 28

What are gap junctions?

Answer 28

A point of cytoplasmic contact between two cells that allows ions and small molecules to move between cell cytoplasms via protein bridges.

Question 29

What cell junction allows for rapid intercellular communication?

Answer 29

Gap junctions

Question 30

Where do the materials of the extracellular matrix come from?

Answer 30

The are secreted from the cell via consituitive exocytosis.

Question 31

What is the most common category of proteins in the ECM?

Answer 31

Glycoproteins.

Question 32

What are glycoproteins?

Answer 32

Proteins with added carbohydrate groups.

Question 33

What is the most abundant protein in the extracellular matrix?

Answer 33

Collagen

Question 34

What are collagen fibres in the extracellular matrix embedded in?

Answer 34

Proteoglycans.

Question 35

What are proteoglycans?

Answer 35

Proteins with extensive sugar additions that exist in the extracellular matrix, embedded with collagen.

Question 36

What component of the ECM allows it to resist compression? And how?

Answer 36

Proteoglycans - They trap water, which resists breakage when compressed.

Question 37

What are fibronectins?

Answer 37

Glycoproteins that attach cells to components of the ECM.

Question 38

What are integrins?

Answer 38

Membrane proteins that connect the ECM to the cytoskeleton, allowing them to communicate.

Question 39

What is the most dynamic cytoplasmic protein structure?

Answer 39

Actin (microfilaments)