2.5- factors affecting membrane structure and permeability

give 5 factors that affect membrane structure and permeability

temperature, fatty acids, cholesterol, organic solvents, proteins

define what happens when you increase/ decrease the temperature

increase- more permeability and kinetic energy so the molecules move faster

decrease- lowers kinetic energy so molecules move slower and less permeability

how do many organisms lose or gain heat?

due to their environment

give 3 things that happen when the temperature drops 

1- saturated fatty acids become compressed and unsaturated fatty acids ,that make up the cell membrane, become compressed and the kinks in their tails push adjacent phospholipids away to maintain membrane fluidity 

2- so these proportions within a cell membrane determine the membrane’s fluidity at cold temperatures

3- cholesterol also buffers the effect of lowered temperature in order to prevent a reduction in the membrane’s fluidity (it does this by preventing the phospholipid molecules from packing together too closely) 

how do some animals adapt their membranes to respond to lower temperatures?

they can change the composition of the fatty acids in their cell membranes (e.g. the atlantic cod)

describe 3 things that occur when the temperature increases in a cell membrane

1- membranes increase fluidity which may change the ability of cells to signal to other cells (by releasing chemicals)

2- cholesterol buffers the membrane by reducing the increase in fluidity caused by rising temperatures

3- the positioning and functioning of protein in the bilayer could drift sideways which may alter the rate of reactions they catalyze

what happens to proteins when you increase the temperature?

the atoms within their large molecules can start to vibrate which breaks the hydrogen and ionic bonds that hold their structure together- so they unfold

-then they denature

what can occur when the proteins start to denature due to high temperature?

the entire plasma membrane can fall apart because they help hold it together and it will become more permeable as holes appear

how does proteins changing shape have an impact on enzymes?

many proteins in the membrane act as enzymes, but if the proteins denature, their active site changes shape so they either stop working or the rate of reaction they catalyze can slow down a lot 

how do solvents affect the phospholipids?

organic solvents such as acetone and ethanol will damage cell membranes as they dissolve lipids

how do heat-shock proteins affect membrane structure and permeability?

they decrease the membrane fluidity by stabilizing the membrane structure under stress conditions, preventing excess fluidity