Unit 3: Intercellular Junctions

Question 1

What are the different types of junctions in animal cells?

Answer 1

Anchoring Junctions
Tight Junctions
Gap Junctions

Question 2

What is the function of achoring junctions?

Answer 2

Mechanically keep cells together

• “spots” between two cells or between cells and connective tissue
• keeps cells attached

Question 3

What is the structure of anchoring junctions?

Answer 3

Plaques on inner surface of cell membrane(s).
Intermediate filaments reinforce to plaques.
Transmembrane proteins connect plaques from adjacent cells.
Keratin filaments reinforce desmosome in intercellular space.

Question 4

What are the different types of anchoring junctions?

Answer 4

Desmosomes
Adheren Junctions (hemidesmosomes)

Question 5

What are desmosomes?

Answer 5

Junctions between cells

Question 6

What are adheren junctions (hemidesmosomes)?

Answer 6

junctions between cells and connective tissue

Question 7

What is the structure of tight junctions?

Answer 7

Rows of tightly packed particles
Structure varies by cell type
number of strands differ
pattern of strands differ

• Prevent fluid from passaing between cells
  ex: cells lining GI tract,, in sperm-producing cells in testes, skin cells
• restrict the movement of membrane proteins

Question 8

What are the functions of tight junctions?

Answer 8

i. prevent leakage of extracellular fluid
Found between cells that line all cavities of mammalian body
ii. establish polarity of cell membrane
Prevents membrane prtoeins from diffusing throughout the membrane

Question 9

What are examples of tight junctions?

Answer 9

i. intestinal epithelial cells
ii. blood-testes barrier
iii. prevent water toss between skin cells

Question 10

What is the structure of gap junctions?

Answer 10

tunnels connecting cytoplasm of adjacent cell

Small pores lined with proteins (can open and close)

Question 11

What is the function of gap junctions?

Answer 11

allow passage between cells of ions and small molecules

Question 12

What is the type of junction found in plant cells?

Answer 12

Plasmodesmata

Question 13

What is the structure of plasmodesmata?

Answer 13

channels through cell walls of adjacent cells

plasma membrane of adjacent cells is continuous

Question 14

what is the function of plasmodesmata?

Answer 14

Passage/tunnel between plant cells

Lateral transport of water and solutes

Question 15

What is an example of plasmodesmata?

Answer 15

with chloride channel, the chloride ions can’t leave the cell