regulation of animal cell shape (lecture 5)

Question 1

outline the importance of the cytoskeleton and its three main components

Answer 1

• helps maintain cell shape and position of organelles
• can rapidly assemble and disassemble to rapidly change cell shape
• highly dynamic, but provides stability
• 3 main components:
  microtubules
  microfilaments
  intermediate filaments

Question 2

explain the role of microtubules (cytoskeleton)

Answer 2

• radiate out from a centrosome during mitosis
• resist compression
• maintain cell shape (due to its larger structure)
• organelle motility (is the path for motor proteins to walk along & aids vesicle transport within the cell)

Question 3

explain the role of microfilaments (cytoskeleton)

Answer 3

• formation of linear strands, and 3d networks
• resist tension
• another cell shape maintainer structurally formed by a double chain of actin subunits
• reduces the fluidity under the plasma membrane
• support cell movement
• actin-myosin interactions allowing for muscle contraction

Question 4

explain the role of intermediate filaments (cytoskeleton)

Answer 4

• made from various proteins (keratins, lamins, neurofilaments)
• supercoiled into cable structure
• least dynamic of the three within the cytoplasm (microtubules & microfilaments)
• form relatively permanent cell structure
• maintain cell shape & anchor organelles
• remain once their creator cell dies eg hair & outer layer of skin

Question 5

outline the importance of cell junctions

Answer 5

• cell-cell communication
• joining together of cells along the ECM extracellular matrix
• cell connection
• maintenance of intracellular contents

Question 6

name the three types of cell junctions and their main function

Answer 6

tight junctions:
hols or seal cells tightly together preventing unwanted movement of fluid across cell layers
desmosomes:
attachments between sheets of cells that act like rivets using intermediate filaments for connection
gap junctions:
cytoplasmic contact between cells to allow ions and small molecules to move from cell to cell and rapid intercellular communication

Question 7

describe the structure and function of the extracellular matrix (ECM)

Answer 7

• composed of material secreted by cells by constitutive exocytosis
• most ECM proteins are glycoproteins and collagen is the most abundant
• collagen fibres are embedded in a proteoglycan (proteins with extensive sugar additions and trap water within the ECM) complex matrix
• water trapped by the proteoglycans help retain tissue shape due to them resisting compression
• fibronectins (glycoprotein) attach to cells in the ECM

Question 8

how is the cytoskeleton connected to the ECM

Answer 8

Integrins (membrane proteins) providing a link of communication between the ECM & cytoskeleton