The Effect of Temperature on the Permeability of Cell Membranes free essay sample

The effect of temperature on the permeability of cell membranes Introduction For my coursework, I intend to assess how temperature affects the plasma membrane of a cell. For this I will use the cell of a beetroot. Background What is a cell membrane? The cell membrane, also called the plasma membrane is a semipermeable lipid bilayer which is the surface of all cells that surrounds the cytoplasm. The membrane is called a bilayer as it has a double layer of phospholipids. Within the cell membrane there are many biological molecules, proteins and lipids, which are involved in cellular processes, and also serves as the attachment point for both the intracellular cytoskeleton and, if present, the cell wall. It is selectively permeable and chooses what molecules enter and leaves the cell and also maintains the cells potential. This following picture is a diagram of the fluid mosaic with all the different molecules labeled: Phospholipids – Phospholipids are a type of lipids which are key parts of all biological molecules, along with glycolipids, carbohydrates and proteins. We will write a custom essay sample on The Effect of Temperature on the Permeability of Cell Membranes or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page The circular head of the phospholipid is the phosphate component. This is hydrophilic (Water Liking) therefore faces the aqueous part that surrounds the membrane. The tail of the phospholipid is the fatty acid component. This is the opposite of the phosphate as it is hydrophobic (Dislikes Water) therefore the tails point inwards towards each other as it is a bilayer forming a non-polar interior. Cholesterol- Cholesterols are the lipids found in the membranes of all tissues. The name cholesterol comes from the Greek words chole (Bile) and stereos (solid). The phospholipid molecule is like the cholesterol molecule in the way that the cholesterol also has hydrophilic (Water Liking) heads and hydrophobic (Dislikes Water) tails, therefore they are able to fit between the phospholipid molecules. The cholesterol molecule helps keeps the fluidity of the cell membrane balanced so it’s not too fluid like or solid. It is also very important to the membrane as its keep it stable and without the cholesterol the membrane would break and the cell will burst open. Protiens- The cell membrane plays host to the protein as it is one of the more popular parts of a membrane that is responsible for its many different activities. Protiens are very important in a membrane as they have many tasks, most of the proteins act as transport proteins. These are used for bigger molecules like polar molecues and ions. There are a different variety of proteins each one for a different type of ion or molecule and they each control what enters and leave the cell. An important type of protein within the cell membrane is the globular protein. Unlike the proteins that only play a structural task, globular proteins work as enzymes, messengers, transporters and supply of amino acids. Some proteins molecules move around with the phospholipid layers whereas some proteins are fixed inside the cell and don’t move and some proteins are also fixed in the outer layer there are also some in the inner layer and proteins around with the whole membrane. Other proteins could also act as enzymes. Protiens are also important in the roles in the membrane s of organelles. E. g. Membranes of mitochondria and chloroplast, as they are involved in the process of respiration and hotosynthesis. Glycolipids- Many molecules including glycolipids on the surface of the membrane have carbohydrate chains connected to them. This combination is known as glycolipids or if a protein is attached then glycoprotein. Environmental Conditions on a Cell Membrane- The phospholipid bilayer is affected when the temperature of the environment it is in is incr eased on the membrane. When the temperature of the membrane is increased the protein starts to denature when the temperature is increased to about 35/45 Â °c and more. Once the proteins have started to denature they gradually start to change shape therefore the shape of the phospholipid bilayer also starts to change shape. At this stage the proteins haven’t fully denatured, but when the temperature is raised to about 65/70Â °c the protein will be fully denatured. Therefore as the protein has completely been denature, the shape of the protein will be completely deformed so, therefore it won’t fit properly into the phospholipid bilayer. Due to this, gaps will appear, making it more permeable. Similarly with the phospholipids, they don’t denature but as the temperature is increases they gain more energy and as a result of this they start to move around. This will cause fluidity of the membrane. This will make gaps and cause it to become more permeable. (References: Biology 1- Mary Jones, Richard Fosbery and Dennis Taylor, http://en. wikipedia. org/wiki/Cell_membrane) Prediction As you can see I have done some research about plasma membranes and its components and I have come to a prediction on what I think will happen and what results might show when I have completed the experiment. I simply predict that the greater the temperature on the beetroot sample the less light will pass through the beetroot sample when it is in the calorimeter and the lower the temperature is more light will pass through the beetroot sample. I have predicted the above because once the temperature is raised to about 35/45 Â °c the proteins in the phospholipid bilayer start to change shape and once the temperature has been raised to about 65/70Â ° the shape would have completely changed and the protein would have fully denatured and the proteins embedded in the phospholipid bilayer will not be able to fit in the bilayer properly. As the temperature is increase not only will the proteins get denatured but the phospholipids will gain energy therefore will start to move faster and the phospholipids will gain fluidity and this will also increase the rate in which permeability is taking place. Therefore, for these particular reason gaps will be made in the phospholipid bilayer due to the denatured proteins and the movement of the phospholipids. As a result, the increase in temperature will have caused damage to the plasma membrane and this will let the red/purple pigment of the beetroot sample (betacyanin) out from the vacuole in which it is held in. Apparatus Beetroot- I am going to use this as I am going to test the permeability of the beetroot cell. Scapula- I will use this to cut the beetroot. Ruler- This will be needed to measure the beetroot. Beaker- I will use this as a water bath and to heat the test tubes in. Pipette- I will use this to get an accurate 4cm? sample of beetroot. Test tube- I will use this to put 15cm? of distilled water and beetroot. Distilled water- I will use this for the experiment as the tap water could have other chemicals for example chlorine. Calorimeter- This will be used in the experiment to calculate how much light is transmitted through the beetroot sample. Cuvette- This will be used to but the sample of beetroot in and put in the calorimeter. Bunsen Burner- This will be used to heat up the water bath. Thermometer- I will use this to measure the temperature of the test tubes in the water bath. Measuring cylinder- I will use this to measure out 15? of distilled water. Cork borer- I will use this to extract small pieces of the beetroot out of the actual one Test tube rack- I will need this to hold the test tubes. Timer- I will need to time how long I have kept the beetroot in the distilled water. Goggles- I will need to wear these so nothing enters my eyes Risk Assessment Equipment/SubstanceRiskReduction/Emergency Action ScapulaRisk of getting cutBe as careful as possible and if cut wash the cut in case of infection and use a first aid kit Bunsen BurnerRisk of getting burntTie hair back, wear goggles and if burnt then put the area which is burnt under cold water Hot waterRisk of getting burntIf burnt, place burnt rea under cold water Beetroot SolutionRisk of entering eyeTo prevent this wear goggles and if it enters eyes wash out with warm water Cork BorerRisk of getting cut Method To begin with I will use a cork borer and get 15 pieces of beetroot and use a ruler to measure each piece 2cm long and cut it using a scalpel as I will be using 5 different temperatures (25Â °c, 35Â °c, 45Â °c, 55Â °c, and 65Â °c). I will repeat each temp erature 3 times. Each piece of beetroot will have to be of the same size to make it a fair test and that is also why I will repeat each with temperature 3 times. Secondly I will then rinse the equal pieces of beetroot with distilled water and dry them as while cutting the beetroot cells could get damaged and therefore betacyanin would be on the samples and this would not be a fair test. After that I will then measure 15cm? of distilled water into a measuring cylinder and pour it out into a test tube. I will repeat this three times. After that a Bunsen burner will need to be set up and as it is a dangerous piece of equipment I will need to wear goggles when using it. Once the Bunsen burner is ready to use I will fill a beaker up with 150 cm? f water and as I will be using the water beaker as a water bath for the test tube I will need to use a tripod and put gauze onto top of it. I will then place the beaker on top of the tripod and on the Bunsen burner. After this I will put the test tubes into the beaker to get the water to the correct temperature. To analyze the temperature I will place a thermometer a test tube till it reaches the first tem perature of my choice which will be 25Â °c. Once the temperature reading is 25Â °c I will remove the Bunsen burner from underneath the beaker. Then I will pace the three test tubes in a holder and at the same time will put 1 beetroot piece in each test tube and keep them all in for four minutes, i will time it using a timer. When four minutes is over I will stir the beetroot solution so no pigment is left at the bottom of the test tube. Using a pipet I will extract 4cm? from each of the solutions and put them into a cuvette, but is important not to touch the cuvette where there are no arrows as that is where the light transmits through. Finally I will use the calorimeter to measure how much light is transmitted through the beetroot samples. But before putting each sample into the calorimeter I will put a sample of distilled water which should measure about 100 so that I will know that the calorimeter has correctly been adjusted. I will repeat this three times for each temperature. I will repeat this procedure all together five times as there are five temperatures, (25Â °c, 35Â °c, 45Â °c, 55Â °c, and 65Â °c) and test one temperature three times just as this is mentioned above.