Investigation into the effect of variation in temperature on the permeability of cell membranes using fresh beetroot.
Identification of trends and patterns
As the temperature was raised, more pigment leaked out of the beetroot disks, which in turn meant that less light was able to be transmitted through the liquid. For example, at 80°c the percentage light transmission through the liquid was 0%. At 20°c the percentage light transmission through the liquid was 76%. This proving the above statement.
Beetroot are eukaryotic cells, and contain many organelles, many of which are bound inside a membrane. Betacyanin is the pigment which gives beetroot its dark red-purple colour, and is stored within the cells vacuole. In order for the betacyanin to leave the cell, it must first pass through the membrane surrounding the vacuole, then the cell surface membrane. Normally the membrane, which is made up of a phospholipid bilayer is quite strong, and no pigment can permeate it. The phospholipid bilayer is made up of water loving hydrophilic heads with water hating hydrophobic tails, together making a phospholipid. The heads line themselves up nearest the water, with the tails in the middle. Phospholipids create bilayers, meaning that you have a line of phospholipid heads facing out towards the water, with the tails facing in, and then another line of phospholipids with the tails pointing towards the original line of phospholipid tails.
When you heat this, the water surrounding the membranes expands, and molecules gain more kinetic energy and vibrate around more. This disrupts the phospholipid bilayer. The more you heat the beetroot, the more the phospholipid bilayer is disrupted, meaning more betacyanin can leak out of the vacuole. Another big factor in the breaking of the membrane is that the beetroot contains some protein, and when this is heated the amino acids uncoil, breaking the hydrogen bonds and disulphide bridges. This then leaves holes in the...