2. 1 Integrating cells into Tissues

Question 1

What are the 3 types of junction that connect cells on their lateral domain?

Answer 1

Tight junctions, Desmosomes and Gap junctions

Question 2

Explain the structure and function of a tight junction.

Answer 2

Fusion of the plasmalemma firmly adheres cells.
It forms an impenetrable seal which prevents molecules and bacteria passing into the cells without having to pass through them.
E.g Intestine epithelium

Question 3

What are desmosomes and where are they found?

Answer 3

Proteins which interlock and connect the cells to further strengthen the bond.
Resist stretching and twisting
Found next to tight junctions.
E.g Skin

Question 4

How does the function of Gap junctions differ to tight junctions and desmosomes?

Answer 4

Proteins called connexons form pores between the cells, allowing passage of small molecules and ions between them. This allows communication and coordination, for example in cilia movement.

Question 5

What are cells anchored to on their basal domain?

Answer 5

Basement membrane

Question 6

What overlies and underlies the basement membrane?

Answer 6

epithelial cells overly the membrane and connective tissue underlies it.

Question 7

What is the name of the 2 methods of basal attachment?

Answer 7

1. Focal adhesions

2. Hemidesmosomes

Question 8

Explain how hemidesmosomes work.

Answer 8

They connect the epithelial cells to the basal membrane via transmembrane integrin proteins.

Question 9

What are focal adhesions?

Answer 9

They anchor the cytoskeleton (actin) filaments to the extracellular matrix via integrin.

Question 10

How would you describe integrins? Summarise their main 2 roles.

Answer 10

Integrins are transmembrne proteins that function mechanically to attach the cell to ECM, but also to sense whether the adhesion has occurred, as they also have a role in signal transduction from ECM to the cell.

Question 11

Compare and contrast necrosis and apoptosis.

Answer 11

Both are mechanisms of cell death. Apoptosis is a controlled mechanism which does not stimulate an inflammatory response. The chromatin is condensed and cell contents re-packaged and phagocytosed.
Necrosis is when the cell swells and bursts, stimulating an inflammatory response as cytotoxic cell components are released. chromatin clumps.

Question 12

If a cell was placed in a HYPERtonic solution, how would water move?

Answer 12

Osmosis out of the cell to area of high solute concentration.

Question 13

In a hypotonic solution, is the solute concentration greater outside or inside the cell?

Answer 13

Inside the cell.

Water movement into the cell to an area of high solute concentration.

Question 14

Which type of adipocyte is unilocular with a nucleus displaced to one side?

Answer 14

White adipocytes

Question 15

What are the functions of adipocytes?

Answer 15

• fuel storage
• thermal insulation
• shock absorption

Question 16

How do brown adipocytes differ from white adipocytes?

Answer 16

Brown adipocytes are multilocular with a central nucleus. They have a rich vascular supply and abundant mitochondria with a role in non-shivering thermogenesis.

Question 17

What transporter prevents cells from swelling and bursting, why is this?

Answer 17

Na+/K+ ATPase. It pumps 2K+ in and 3Na+ out of the cell, leading to a net loss of osmotically active ions.

Question 18

What is the plasma concentration and the intracellular concentration of sodium?

Answer 18

Plasma: 140 mmol/L
Intracellular: 14 mmol/L

Question 19

What is the plasma and intracellular concentration of potassium?

Answer 19

Plasma: 5 mmol/L
Intracellular: 160 mmol/L

Question 20

Other than organ failure, what is a common cause of low pH?

Answer 20

poor tissue perfusion, as it leads to anaerobic glycolysis and lactate production which lowers pH.