Factors influencing membrane permeability and the hemolysis of red blood cells
Sitara Koneru
Introduction
Cell membranes are part of both prokaryotic and eukaryotic cells and serve to regulate the transport of particles in and out of the cell, communicate with the environment, and define the boundary of the cell. They are composed of a phospholipid bilayer, proteins, and carbohydrates and described by the fluid mosaic model. Solvents pass through the membrane via two different methods: diffusion and active transport.
Diffusion does not require any energy as the molecules move from areas of high concentration to areas of low concentration, also known as moving down the concentration gradient. However, not all molecules can passively move through the membrane due to characteristics such as size, polarity, and electrical charge. Facilitated diffusion is a type of diffusion where a protein assists the molecule cross the membrane.
It is still diffusion, therefore the molecule still moves down the concentration gradient and does not require the input of energy. Active transport moves molecules up the concentration gradient and requires the input of energy. Osmosis is another type of diffusion in which water moves across a cellular membrane. For a system to attain equilibrium through osmosis a concentration gradient must be established and the membrane has to be permeable to water but impermeable to the solute (Becker, et al., 2009).
Oxygen and carbon dioxide are transferred between the environment and red blood cells by osmosis. Red blood cells have membranes that are permeable to water but only semi-permeable to other molecules. While water continually moves through the cell,

it grows in size and eventually ruptures. The process of a cell bursting is known as hemolysis (Membrane Permeability). Studying hemolysis has led to the conclusion that it can occur due to diseases like malaria as an effect of certain medications, such as
Levodopa, an anti-Parkinson’s drug (Territo et al., 1973). Hemolysis can be better understood if the reaction of a red blood cell to different conditions, such as varying molecular weights, is better understood. MacGregor and Tobias studied the effects of molecular weight regarding slow hemolysis by gradually changing the solute concentration until hemolysis took place. They discovered that out of all the molecules they tested, lithium chloride had the greatest effect on hemolysis due largely to its small size (MacGregor and Tobias, 1972).
In this experiment, I inquired whether or not molecular weight affected the rate of hemolysis. I predicted that the rate of hemolysis of the blood cell would decrease as molecular weight increased and hypothesized that there was an indirect relationship between the rate red blood cells hemolyze and the molecular weight of the solute.
Methods
To test the effects of molecular weight, urea, methylurea, diethylurea, and dimethylurea were used. A blank was created by adding a sheep red blood cell suspension (SRBC) into a test tube containing water. This tube was set aside for ten to fifteen minutes. During this