Cell Permeability Cell membrane permeability refer to the crossing of the cell membrane by substances. Substances move into or out of the cell by crossing the cell membrane. Some substances cross the membrane very easily and the membrane is said to be very permeable to these substances; others move across with difficulty, while others are excluded completely. There are various process that a substance may used to cross the cell membrane, such as diffusion, facilitalated diffision, or a substance may inter a cell by a mean of a cell membrane carrier, which requires some kind of energy, such as ATP. In any of the process that a substance may used to cross the cell membrane it has to be determined by the gradient of that particular substance that is crossing, that is the charge that the gradient has or the concentration of that particular substance making its way into the cell by passing the cell membrane.
Other important aspect of cell membrane permeability is the rate of the substance to cross the cell membrane, which depends on what kind of cell it is or what is the substance that is trying to cross the membrane. This experiment is divided into three parts as follow: (A) Hemolysis of Erythrocytes, (B) Hemolysis and phylogenetic relationships, and (C) Permeability of cell membrane in relation to fat solubility. Part A, Hemolysis of Erythocytes, the concentration of each solute that will produce hemolysis on red blood cells. The concentration is measure by using different solute such as sucrose, sodium sulfate, and calcium chloride. Each of the measurements had been measure in units of osmolar since it is the measure of effective solute concentration and is dependent on the number of active particles and not on the kind of particles Part (B) is hemolysis and phylogenetic relationships is to measure the times of hemolysis, the rapture of the cell capsule, for the rat blood.
The different solutes that were used to measure the time of hemolysis are urea, ethylene glycol, thiourea, and glycerol. Depending of the molecular weight of the solute, that is going to be the amount of time that it would take for the red blood cells to reach hemolysis, there are other factors that are involved in determining the time of hemolysis, these are going to be known when the results for the experiment stated on the results section of the report. Also, in these part of the experiment comparison between human, rat, and mouse red blood cells are going to make. Part (C) is permeability of cell membrane in relation to fat solubility, many fat compounds enter the cell membrane depending on the fat solubility that the substance contain. One of the main aspects that has a lot to do on the solubility of the substance to enter the cell membrane mostly depends on the partition coefficient that the cell membrane enclose. The substances that are being used in this part of the experiement to test the lipid or fat solubility are being tested are alcohols such as, methyl alcohol, ethyl alcohol, and propyl alcohol. Methods Part A Hemolysis of Erythrocytes – Rat blood is going to be used throughtout the experiment.
– Add 5 drops of rat blood to the suspension that was prepare from solute and water (see handout p. 4). – Inversed test tube and check for hemolysis within 30 seconds (handout p. 4). Part B Hemolysis and phylogenetic relationships – Add 5 drops of rat blood to 2ml of each of the solutions being used (see handout p. 5).
– The following solutions are being used for this section: Urea, Ethylene Glycol, Thiourea, and Glycerol. Part C Permeability of cell membrane in relation to fat solubility – Add five drops of rat blood to 2ml of isosmotic solution and note time of hemolysis as before (see handout p. 5). – Solutions being used: methyl alcohol, ethyl alcohol, and propyl alcohol. Results Part A Hemolysis of Erythrocytes In this part of the experiment it is determinated the concentration of each of the the solutions being used which just produces hemolysis.
Solution Concentration (mOsm) Contribution per mM NaCl 95 1.86 Sucrose 89 1.0 Na2SO4 99 2.9 CaCl2 104 2.6 For this section of the experiment one have to understand that the osmotic pressure of the red blood cells is 300 mOsm, and from the concentration that we acquired during the experiment we conclude that rat blood cells will go into hemolysis since their osmotic pressure this different and a equilibrium can not be obtain. From the data above one can determinate that sucrose has the lower concentration since it molarity is low compared to the others, and its membrane permeability is low compared to the others solutions such as NaCl and Na2SO4. CaCl2 on the other hand, has the higher concentration and the highest molarity of all the solution, its molarity is about 0.08 0.10, and its membrane permeability would need more concentration of it to pemetrate the cell membrane. Each of the solution also has its own contribution per mM to its concentration, this it more like a reference for to its molarity of each solution. Part B Hemolysis and phylogenetic relationships The times to hemolysis for rat blood, human blood, and mouse blood.
Solute Human Rat Mouse urea (60.1) 7 (secs) 5 (secs) 2 (secs) ethylene glycol (62.1) 18 10 4 thiourea (76.1) 75 29 10 glycerol (92.1) 27 16 25 During this part of the experiment we determinated the time of hemolysis of red blood cells in ososmotic solutions (300 mOsm). Solution Molecular Weight Urea 60.1 Ethylene Glycol 62.1 Thiourea 76.1 Glycerol 92.1 Human red blood cells takes longer to hemolysis since they are bigger cells compare to rat or mouse red blood cells. One can conclude from the molecular weights of the molecules that the way in which the molecules will get into the cell will be first Urea, Ehtylene Glycol, Thiourea, and finally Glycerol. But, one of the most interesting part of the graph is that one can see that Glycerol being the biggest molecule reached hemolysis faster, in less time, than Thiourea being smallest molecule, but this only happens in human and rat red blood cells. This is because the cells in a human and rat blood likes Glycerol and most imporantantly it has its own channel that it can used to get in faster. On the other hand, Thiourea dont have its own channel and it has to diffuse into the cells which will a longer time.
In mouse red blood cells dont have this special Glycerol channel and one can see from the graph that it will the molecule of Glycerol will take longer to diffuse into the cell because it is the biggest molecule. Part C Permeability of cell membrane in relation to fat solubility The times for hemolysis of rat red blood cells for the alcohols. Alcohol Time for hemolysis (secs) methyl alcohol (0.0097 p.c.) 11 ethyl alcohol (0.0357) 8 propyl alcohol (0.156) 2 This compounds enter the cell membrane in relation to its fat solubility, the factor to measure the fat solubility in this case is deteminated by the partitian coefficient. In the table and graph above we can see that even thought, propyl alcohol has the longer length of carbon chain it entered the cell membrane first. The entering of propyl alcohol first to the cell membrane its due to the fact that it has the highest partitian coeffient between the three alcohols presented during this experiment. The highest the partitian coeffiecient for a compound is the highest increase of lipid solubility it has, and as a result it would enter the cell membrane faster. Also it can be said that all of this compound with partitian coefficienct are also non-polar compounds with means that they are compound that have equally amount of electrons being shared.