5.2 : Factors Affecting Membrane Structure Flashcards
How does temperature affect membrane structure?
Phospholipids in a cell membrane are constantly moving.
When temp increases, the phospholipids will have more kinetic energy and will move more.
This makes the membrane more fluid and it begins to lose its structure. If temperature continues to increase the cell will eventually break down completely.
The loss of structure increases the permeability of the membrane, making it easier for particles to cross it.
How does temperature affect proteins in the cell membrane and the fore affect the cell membrane ?
Carrier and channel proteins in the membrane will be denature at higher temperatures.
These proteins are involved in transport across the membrane so as they denature, membrane permeability will be affected.
How do phospholipids react in water?
The non - polar tails of the phospholipids are orientated away from the water, forming a bilayer with a hydrophobic core.
The charged phosphate heads interact with water, helping to keep the bilayer intact.
What happens to cell membranes in organic solvents ? Link this to their uses.
Many organic solvents are less polar than water eg alcohols, or they are non polar eg benzene.
Organic solvents dissolve membranes, disrupting cells.
This is why alcohols are used in antiseptic wipes. The alcohols dissolve the membranes of bacteria in a wound, killing them and reducing the risk of infection.
Describe how different strengths and concentrations of alcohols affect membranes?
Strong / pure alcohol solutions are toxic as they destroy cells.
Less concentrated alcohol solutions such as alcoholic drinks will not dissolve membranes but still cause damage.
The non polar alcohol molecules can enter the cell membrane and the presence of these molecules between the phospholipids disrupts the membrane.
What happens when membranes are disrupted?
They become more fluid and more permeable.
Some cells need intact cell membranes for specific functions, for example, the transmission of nerve impulses by neurones ( nerve cells ).
When neuronal membranes are disrupted, nerve impulses are no longer transmitted as normal.
How do you investigate membrane permeability?
Beetroot cells contain a red pigment , and when disrupted, it is released and the surrounding solution is coloured.
Method:
Wash beetroot and put in distilled water in water bath.
Increase temperature in 10°C intervals.
Samples of water containing beetroot taken five minutes after each temperature was released.
Absorbance of each sample measured using colorimeter with a blue filter.
