Unit 3: Intercellular Junctions

Question 1

True or false: The intercellular junctions between animal cells are different to those between plant cells.

Answer 1

True.

Question 2

What are the 3 types of junctions between animal cells?

Answer 2

1. Anchoring junctions
2. Tight junctions
3. Gap junctions

Question 3

What is the purpose of anchoring junctions?

Answer 3

To mechanically keep cells together.

Question 4

There are 2 types of anchoring junctions, what are they?

Answer 4

Desmosomes and adheren junctions (hemidesmosomes).

Question 5

How are anchoring junctions structured?

Answer 5

• plaques on inner surface of cell membrane(s)
• intermediate filaments reinforce to plaques.
• trans-membrane proteins connect plaques from different cells
• Keratin filaments reinforce desmosome in intercellular space

Question 6

What are the 2 purposes of tight junctions?

Answer 6

1. Prevent leakage of extracellular fluid found between cells that line all cavities of the mammalian body.
2. Establish polarity of cell membrane (prevents membrane proteins from diffusing through the membrane).

Question 7

How are tight junctions structured?

Answer 7

• rows of tightly packed particles

- structure varies by cell type (number of strands differ and the pattern of strands differ)

Question 8

What are 3 examples of tight junctions?

Answer 8

a. intestinal epithelial cells
b. blood-testes barrier
c. prevent water loss between skin cells.

Question 9

What is the main function of gap junctions?

Answer 9

To allow the passage of ions and small molecules between cells.

Question 10

Where are gap junctions found?

Answer 10

In the heart, intestines, pancreas and in embryos.

Question 11

How are gap junctions structured?

Answer 11

• Tunnels connecting cytoplasm of adjacent cell

- Small pores lined with proteins (that can open and close)

Question 12

What are the intercellular junctions found in plants?

Answer 12

Plasmodesmata

Question 13

What is the function of plasmodesmata?

Answer 13

Lateral transport of water and solutes.

Question 14

What is the structure of plasmodesmata?

Answer 14

• channels through cell wall of adjacent cells

- plasma membrane of adjacent cell is continuous