Membrane Permeability Flashcards
What are two factors that affect the structure and permeability of membranes?
Effect of temperature
Effect of solvents
Why does the temperature of many organisms vary with their environment?
Many organisms do not generate heat to maintain their body temperature and so their temperature varies with their environment.
Why does increasing the temperature increase the permeability of membranes?
Increasing the temperature increases the permeability of membranes because…
1. Increasing the temperature gives the molecules MORE KINETIC ENEGRY so they MOVE FASTER- increased rate of diffusion
2. Increased movement of phospholipids and other components which makes membranes LEAKY (increasing fluidity)
As a result this allows substances that would normally not do so enter or leave the cell
3. Also increased temperature can change the ABILITY of cells to signal to other cells
4. Also increased temperature can effect the rate of enzyme controlled reactions inside the cell.
What happens to membrane permeability if the temperature is decreased?
Decreasing the temperature often has little effect on the permeability of the membrane
One reason for this is because of cholesterol
Cholesterol BUFFERS the effect of the lowered temperature to prevent reduction in membranes permeability
It does this by preventing the phospholipid molecules form packing too closely together.
What effect do solvents have on phospholipid ?
Organic solvents e.g. ACETONE or ETHANOL will damage the cell membranes
Because Acetone and ethanol dissolve lipids
