Factors affecting Membrane Permeability

Factors that effect membrane permeability

1) The nature of substance : size / polar non polar

2) presence of transport proteins : Channel + Carrier protein → allow water to pass through

3) temperature effect + Solvents + Cholesterol levels

Temperature ( increase )

Increase in temp = give more kinetic energy to the molecules to move around + faster

• The phospholipid acquires more energy = move around more , which increases the membrane fluidity.

• → affect the unfolding of plasma membrane during phagocytosis.

• Change the ability of cellls to signal to other cells by releasing chemical.

Temperature ( decreasing)

Decrease in temp = decrease in kinetic energy → causing the molecules to slow down

• Saturated fatty acids —> compressed

However : Unsaturated fatty acids make up the cell membrane phospholipid bilayer as they become compressed, the kinks in their tails will push the adjacent phospholipid molecules away. = to maintain the membrane fluidity.

At cold temp : the proportion of unsaturated + saturated fatty acid will determine the membrane’s fluidity.

Cholesterol

Cholesterol acts as a buffers the effect of lowered temp, to prevent a reduction in the membrane’s fluidity

The temperature would need to be known to

conclude what effect cholesterol has

(cholesterol) increases fluidity at low temperatures

(cholesterol) decreases fluidity at ,

high temperatures / body temperature / 36-38°C

o

ne example of other factor that affects fluidity

By preventing the phospholipid molecules from packing together too closely, cuz cholesterol molecules are in between groups of phospholipid molecules.

Effects of solvents on phospholipid

Eg : Acetone & Ethanol will damage cell membrane as they dissolve lipids.