Diffusion in Red Blood Cells - Essay Example

Running Head Diffusion Diffusion in Red Blood Cells The human body is composed of different systems that all work together to maintain an optimum condition for an organism to thrive despite the many changes in the environment. The plasma membrane is one of the control mechanisms at the cellular level that regulate cellular functions. This experiment aims to demonstrate how factors such as temperature affect the rate of diffusion and how different solute concentrations affect the morphology of the red blood cells and how this would translate to clinical practice. The effect of temperature was determined by subjecting the potassium permanganate-water solution to different temperatures. The solution subjected to the highest temperature demonstrated the fastest rate of diffusion. The effect of varying solute concentrations was demonstrated by adding 2 drops of blood to six test tubes each containing different solutes. Crenation was observed in cells put in hypertonic solution, while lyses were observed in cells put in hypotonic solution. Cells put in isotonic solution showed no change in morphology. The effect of detergent was determined by adding 3 drops of detergent on the sodium chloride solution. The packed cell volume was also determined with the use of the microhaematocrit reader. Patients with low hematocrit values suggest anemia, among others, while an increased value would indicate several conditions including polycythemia. INTRODUCTION The human body is one masterpiece that is made up of a complex series of processes that work in coordination with all other bodily systems to maintain a healthy and thriving organism. These processes all happen in a controlled fashion, such that they simultaneously complement the activity of the other processes taking place in the other parts of the body. This is exemplified at the cellular level by the efficiency of the plasma membrane in regulating the flow of substances in and out of the cell. This study has been conducted to differentiate diffusion from osmosis, to define hypertonic, hypotonic and isotonic solutions, to measure packed cell volume and relate all these to the workings of the human body. METHODOLOGY This experiment was made up of three parts. The first part demonstrated the effect of temperature on the rate of diffusion. Crystals of potassium permanganate were placed in beakers which were subjected to different temperatures. Changes in the solutions were observed over a period of time. Observations were noted and recorded at 0 minute, 5 minutes and then at 10-minute intervals for the first hour, and then again after every 20 minutes thereafter. To demonstrate the effect of osmosis on red blood cells, six test tubes were prepared and were labeled test tubes A-F. Two (2) ml of different solutions were placed in each tube with the use of a Pasteur pipette. Two (2) ml of blood was then added to each test tube. After mixing by inversion, the tube was placed in front of a printed page to see if the print can be easily read through the solution. Samples were also taken from each tube using Pasteur pipettes and were placed and viewed on the slide under the microscope at x400 magnification. The effect of detergent was observed by putting 3 drops of detergent on test tube A. The tube was then held against a printed page and was observed. Packed cell volume was determined by taking blood samples into capillary tubes sealed with cristaseal on the unfilled end. The tubes were then placed in a centrifuge and were spun for 10 minutes. Red cell volume was then measured using a microhaematocrit reader. Results from 6 samples were collected and the mean value was then calculated. RESULTS AND DISCUSSION The plasma membrane is a semipermeble membrane which functions to regulate the substances which go inside and outside of the cell. Its structure is made up of a lipid bilayer which is composed almost entirely of phospholipids and cholesterol. One part of the phospholipid and the cholesterol molecules is hydrophilic, or soluble in water, while the other part is hydrophobic or soluble only in fats. Ions, glucose, urea and other water-soluble substances are unable to penetrate the lipid bilayer, while fat-soluble substances such as oxygen, carbon dioxide and alcohol can easily glide through (Guyton, 1992). In order to maintain the integrity of the cell, a dynamic equilibrium must be achieved in the course of the exchange of substances into and out of the cell. The state by which the internal environment of a cell is maintained stable despite the changes in the cell environment is called homeostasis (Marieb, 2003). At the cellular level, homeostasis is made possible by the regulatory function of the plasma membrane. According to Guyton (1992), the adult human body is made up of about 56% fluid. Most of this fluid is found inside the cell, or the intracellular fluid, and about one third is found outside the cell and is aptly called extra cellular fluid. Ions, hormones, neurotransmitters, salts and other nutrients such as amino acids, sugars, fatty acids and vitamins needed for the maintenance of cell life are found in the extra cellular fluid which is in constant motion throughout the body. An exchange of these various substances across the semi-permeable membrane is needed for cellular functions to proceed. Movement across the membrane happens in two ways. It can either be through the passive transport process wherein no energy input is required from the cell, or through the active transport process wherein energy in the form of ATP is required to drive the movement of molecules across the membrane. Diffusion and filtration are two examples of the passive transport process. Marieb (2003) described diffusion as the process by which molecules tend to scatter themselves throughout the available space. The force that drives this process is the kinetic energy that is present in all molecules which are in constant motion and at random collision with each other. The net effect of this action is the movement of the molecules from an area of higher to a lower concentration, an action termed as the movement down the concentration gradient. Factors such as the size of the colliding molecules and temperature affect the evolved kinetic energy such that the bigger the molecular size and the higher temperature, the faster would be the rate of diffusion. For molecules to passively permeate the plasma membrane, they should either be small enough to get through the pores or they should be fat soluble. There are two types of diffusion: simple and facilitated diffusion. Molecules can move through simple diffusion if their size permits them, like the small-sized chloride ions or if they are fat-soluble like some vitamins, fats, oxygen and carbon dioxide. Osmosis is a kind of simple diffusion which refers to the movement of water molecules across a selectively permeable membrane from an area of higher to a lower concentration. Facilitated diffusion, on the other hand, is the movement of molecules across a semipermeable membrane with the help of carrier proteins to facilitate the transport of larger molecules such as glucose, to make it available for cell consumption. The second type of passive transport process, called filtration, is defined as the process by which water and solutes are forced through a membrane by fluid or hydrostatic pressure (Marieb, 2003). Such kind of transport process is exemplified by the functions of the kidneys. This experiment is focused on the movement of molecules via diffusion and osmosis. Blood is the river of life that surges within us, and makes up about 8% of the human body. It is the only tissue in our body that is fluid, making it an efficient means to transport oxygen and other vital nutrients to the different organs of the body. It is produced through the process of hematopoiesis, which takes place in the red bone marrow, also known as the myeloid tissue and is found primarily on the flat bones of the skull, pelvis, ribs, sternum,and proximal epiphysis of the humerus and femur (Marieb, 2003). Gottfried (1994) described blood as being made up of plasma, the liquid portion, and the formed elements (erythrocytes, leukocytes, and platelets) which make up 45% of the blood. Erythrocytes, or red blood cells (RBC) are flat-disc-shaped cells with depressed centers. They contain the oxygen-carrying molecule hemoglobin. Leukocytes, or white blood cells (WBC) are the body’s defense against foreign substances that invade the body and cause diseases. Platelets, on the other hand, are significant figures in blood coagulation. After conducting the experiment on the effect of temperature on the rate of diffusion, the following results were obtained: Table 1. The effect of temperature on diffusion Time elapsed A/60c B/46c C/1c cold D/room temperature 20c 55 bubbles No change No change Full diffusion 45 No change No change No change Part diffusion 35 No change No change A partial diffusion 25 No change No change No change No change 15 No change No change No change No change 0-5 1 minute fully disbursed Disbursed No change No change This clearly demonstrates the direct relationship between temperature and the rate of diffusion. A high temperature would also yield a faster diffusion rate. The following are the results obtained when red blood cells were subjected to solutions of varying concentrations: Table 2. The effect of different solute concentrations on red blood cell Test tube # 1 2 3 4 5 6 Solute 0.9% NaCl 10% NaCl Distilled water 20% Glucose Detergent water Type of solution Isotonic hypertonic hypotonic hypertonic hypertonic hypotonic Observation Poor clarity Poor clarity; moving quickly then settled and motionless Can see print but not clearly Cannot see print No clarity Quite clear; Clear with dark spots 10X40 No change in cell shape Shape of the cell changed Cells lysed Crenation occurred agglutination Cells lysed PCV 42% 41% 40% 42% 43% 43% Mean PCV : 42% Solutions can either be hypertonic, hypotonic or isotonic in nature. A hypertonic solution is one where there are more solutes or dissolved substances outside than inside the cells; a hypotonic solution contains more solutes inside the cell than outside, while and isotonic solution has the same solute and water concentrations as cell do (Marieb 2003). In order for cells to function properly, they need to be exposed to conditions which would favor their growth and development. These conditions include an environment which is most suitable for their functions. When exposed to conditions which are otherwise favorable, cells would respond with ways that would prove damaging to their structure and could potentially lead to cell death. This is the rationale in the health care setting where health care professionals are held responsible for the fluids that they infuse in the intravenous lines of their patients. The results in the preceding table demonstrate how hypertonic, hypotonic and isotonic solutions affect the physiology of the red blood cells. These results, as we will see, would translate to its significance in the field of medicine. The solution in test tube #1 (0.9% NaCl solution) is an example of an isotonic solution. Other examples of such solutions are Ringer’s lactate, 5% dextrose, and 0.9% saline solution. Being an isotonic solution, it has the same concentration as the RBCs in this experiment. As such, there weren’t any visible change observed in the cells’ shape. Test tubes # 2 , 4 and 5 are all hypertonic solutions. Cells put in a hypertonic solution are inclined to release water molecules to their environment where there are fewer of them, which lead crenation, or shrinkage of cells, as exemplified by tubes 2,4 and 5. The release of molecules has caused turbidity in the solution, thereby making the print barely visible. Patients with edema, a condition characterized by too much fluid retention which causes the patient’s hands and feet to swell, are at times given hypertonic solutions. This help draw excessive water out of the cells and into the bloodstream for the kidneys to eliminate (Marieb 2003). Test tubes 3 and 6 are hyptonic solutions. Cells exposed to such solutions would tend to draw water into the cells causing them to take on a globular shape until they finally burst or lyse. This resulted to a solution clear enough to read through the tube. Distilled water is the best example of a hypotonic solution as it contains no solutes at all. Hypotonic solutions are sometimes infused intravenously to extremely dehydrated patients to rehydrate their cells. Athletes who give out excessive water in the form of sweat are often given colas and other sports drinks to bring back the water lost by the cells. A bottle of hypotonic drink does the job of rehydrating and refreshening the cells making the athlete feel energized. (Marieb, 2003). Detergents are soap substitutes that contain non-polar hydrocarbon chains and an ionic group that form water-soluble products. The hydrocarbon end of the detergent molecule is attracted by dirt, oil or grease while the ionic end is attracted by water. These result to an orientation wherein dirt is trapped by water molecules and is readily washed away (Robinson, 1988). This property of detergents might have caused the agglutination in the RBCs. Packed cell volume, or hematocrit is the percent of whole blood that is composed of red blood cells. It is a measure of both the number and size of the red blood cells. The normal values vary with altitude but the average reference values are 40.7 – 50.3% in males and 36.1 – 44.3% in females. Low hematocrit values may indicate anemia, blood loss or hemorrhage, bone marrow failure, destruction of red blood cells, leukemia, malnutrition or specific nutritional deficiency, multiple myeloma or rheumatoid arthritis. High values, on the other hand, may indicate dehydration due to burns or diarrhea, excessive red blood cell production or erythrocytosis, or polycythemia vera (Nanda, 2005). REFERENCES Gottfried, S. (1994). Human biology. USA: Mosby. Guyton, A. (1992). Human physiology and mechanisms of disease. USA: W.B. Saunders. Marieb, E. (2003). Essentials of human anatomy and physiology, 7th ed. California: Pearson Education. Nanda, R. (03 February 2005). Hematocrit. Retrieved 05 April 2006 from http://www.nlm.nih.gov/medlineplus/ency/article/003646.htm Robinson, H. (1988). College chemistry with qualitative analysis, 8th ed. USA: D. C. Heath and Company. Read More