Lecture 6: Regulation of Animal Cell Shape

Question 1

What is the purpose of the cytoskeleton?

Answer 1

Maintain cell shape, position organelles within the cell, disassemble / reassemble so that cell shape can change.

Question 2

Microtubules

Answer 2

Made of tubulin. Function to resist compression. Can provide cell motility through flagella. Transport of organelles by acting as railway track. Can disassemble and reassemble rapidly.

Question 3

Microfilaments

Answer 3

Made of actin. Function to resist tension. Able to produce movement via actin myosin interaction, often found under plasma membrane. Can disassemble and reassemble rapidly.

Question 4

Intermediate Filaments

Answer 4

Half the size of microtubules and microfilaments. Made of proteins such as keratin and are less dynamic then the other two. Function to maintain cell shape and anchor organelles.

Question 5

Tight Junction

Answer 5

Tight junctions as the name suggests hold neighbouring cells tightly pressed together. It may form a continuous seal. They prevent movement of fluid across cell layers. This is very important for certain cells. Take cells found within the digestive system, they don’t want fluid secreting through layers of cells.

Question 6

Gap Junction

Answer 6

Desmosome are an anchoring junction which act as rivets within cells, tight junctions act more as cells sewn together. Provide attachments between sheets of cells and are rather permanent compared to other types of cell connections. This is because they are made up of intermediate filaments, which is the strongest and most permanent filament.

Question 7

Desmosomes

Answer 7

Finally gap junctions are junctions which leave a gap between the cells so that ions and small molecules can be passed between each other. Allows for rapid cell - cell communication.

Question 8

What is the extra cellular matrix composed of?

Answer 8

Glycoproteins such as collagen and proteoglycan. Fibronectin is also found in the ECM.

Question 9

What do proteoglycans do?

Answer 9

Trap water in the ECM. This is important because water resists compression thus helping tissues maintain shape.

Question 10

How is the ECM connected the cytoskeleton? What does this link provide?

Answer 10

The membrane proteins, integrins, connect to a type of glycoprotein in the ECM called fibronectin. This provides a communication link between the ECM and interior of cell.