Download Effect of temperature on membranes

Factors affecting the permeability
of the Cell Membrane
Temperature and
ethanol
You should be able to:

Outline the effects of changing temperature
on membrane structure and permeability
Effect of temperature on Beetroot
Betalain is the pigment that gives beetroot its
dark red colour.
Q:Where is the pigment is found in the living
beetroot cells?
vacuole
Q:What structures does the pigment pass
through to get out of the cells?
Tonoplast and cell surface membrane

Effect of temperature on Beetroot
If you soak pieces of beetroot in water of different
temperatures the following results are obtained.
20oC
Room
45oC
50oC
55oC
60oC
65oC
ethanol
Effect of temperature on Beetroot
Q:Why is the pigment likely to leak out at higher
temperatures?
Increasing temperatures gives molecules more
KINETIC ENERGY
Phospholipids move more quickly at high
temperatures, making the membrane more fluid,
leading to its breakdown and the leakage of the
pigment
Proteins (channel and carrier) are denatured by the
heat so no longer effectively control what enters
and leaves through the membrane.
Effect of temperature on Beetroot
What happens if you use ethanol?
Does this cause the pigments to leak out at lower
temperatures than water?
Does ethanol have any chemical properties that are
different from water that might affect the
"waterproofing" of the cell membrane?
Ethanol can dissolve phospholipids, and so can
act like a detergent - punching holes in
membranes.