Cell Membrane Fluidity

Cell Membrane Fluidity

• parameter describing the freedom of movement of the protein and lipid components within a cell membrane

Factors affecting fluidity

• Length and degree of saturation of fatty acids

• Temperature

• Cholesterol Content

Reasons for regulating fluidity

• makes sure the cell can move

• allows substances to cross the membrane

• too fluid - can’t control what substances enter

cholesterol

• steroid molecule - flat irregular structure

• slightly polar at one end

cholesterol is found in what type of cell

• animal cells only

cholesterol in plant cells

• phytosterol

use of cholesterol

• regulates membrane fluidity

• acts as a buffer

how does cholesterol function as a buffer

• regulates temperatures and degree of saturation of fatty acids from increasing or decreasing fluidity

effect of saturation of fatty acids on fluidity

• unsaturated fatty acids = more kinks = higher fluidity

• saturated fatty acids = straight tails/more compact = decrease fluidity

effect of length of fatty acids on fluidity - how does cholesterol counteract this

• short chain unsaturated fatty acids increase fluidity - cholesterol fits in the gaps to mitigate this

• long chain saturated fatty acids decrease fluidity - cholesterol disrupts close packing of the phospholipid molecule

effect of temperature on fluidity + cholesterol

• low temperature decrease fluidity tails become more packed together - cholesterol mitigates close packing

• high temperature increase fluidity - cholesterol contrains motion

bacteria and fluidity regulation

• enzyme fatty acid desaturases

• low temps - introduces double bonds which increases fluidity

• (high temps - activity decreases and single bonds are introduced)