March 6th - Osmotic Stress

Question 1

Osmotic stress occurs

Answer 1

when ion and water balance are disrupted
(balance meaning normal homeostatic state)

Question 2

hyperosmotic environment causes…

Answer 2

water to leave the cell, cell size to decrease, [ions + other solutes] in the cell then increases

Question 3

hypoosmotic enviro causes…

Answer 3

water to enter the cell, cell size increases, [ions + other solutes] in cell decreases

Question 4

ice can cause osmotic stress because ….

Answer 4

1. When water is converted to ice, there is less liquid water
2. When ice melts to water, there is more liquid water
3. Changes in osmolarity → changes in cell volume which can cause stretching/ compression on cell membrane and potentially cell death
4. increases/ decreases in cell volume changes concentration of many solutes in the cell

Question 5

higher osmolarity

Answer 5

less susceptible to stress from freezing and/or other osmotic stress

• less ice forming b/c of more solutes

Question 6

Strategies for dealing w osmotic stress from freezing

Answer 6

1. minimize changes in cell water content
   -less ice=less osmotic stress
   ex. accumulate compatible osmolytes to increase osmolarity
2. accumulate molecules to protect membranes and proteins
   ex. cryoprotectants and chaperone proteins