Regulation of Cell Shape

Question 1

What is a cytoskeleton?

Answer 1

Helps to maintain cell shape and position of organelles in cells. Composed of three main components : microtubules, microfilaments and intermediate filaments

Question 2

What is the cytoskeletons function?

Answer 2

Rapidly dissembles and reassembles allowing rapid changes in cell shape
Highly dynamic but still provides stability

Question 3

What are Microtubules?

Answer 3

Microtubules are composed of tubulin subunits which may radiate out from a centrosome. They resist compression and maintain cell shape. Can also provide cell motility : flagella and cilia

Question 4

How are microtubules involved in organelle motility?

Answer 4

• ATP powered motor proteins can walk organelles along microtubules
• Allows vesicles or other organelles to be transported to specific targets within the cell

Question 5

What are microfilaments?

Answer 5

Double chain of actin subunits, form linear strands and 3D networks. Microfilaments resist tension and the outermost part helps make the plasma membrane less fluid and maintains cell shape

Question 6

What are intermediate filaments?

Answer 6

Made of various proteins, supercoiled, less dynamic than microtubules or microfilaments, form relatively permanent cellular structures. Help maintain cell shape and anchor organelles. May also remain after death of cell

Question 7

What are tight junctions?

Answer 7

• Hold neighbouring cells tightly pressed together
• May form a continuous seal
• Prevents movement of fluid across cell layers

Question 8

What are Desmosomes?

Answer 8

• Anchoring junctions
• Provide attachments between sheets of cells
• Acts like rivets
• Connected into the cell by intermediate filaments

Question 9

What are gap junctions?

Answer 9

• A point of cytoplasmic contact between two cells
• Ions and small molecules can pass from cell to cell
• Allows rapid cell to cell communication

Question 10

What is the extracellular matrix (ECM) ?

Answer 10

• Composed of material secreted by cells (secretion occurs by exocytosis)
• Most ECM proteins are glycoproteins -> most abundant is collagen
• Collagen fibres embedded in proteoglycan -> trap water in ECM
• Water resists compression and helps retain tissue shape