The cytoplasm and extracellular environment of the cell are aqueous solutions. They are primarily composed of water (the solvent), and a variety of dissolved solutes, such as sugars, amino acids, and ions. The plasma membrane of the cell is selectively permeable, allowing water to freely pass through, but regulating the movement of solutes. Water and some dissolved solutes move via passive diffusion through the plasma membrane. Diffusion is a process where molecules move from an area of high concentration to an area of low concentration. How quickly diffusion occurs is dependent on several factors, such as temperature, particle size, and the concentration difference on either side of the membrane. Testing the hypothesis relating to the effect of molecular weight to the diffusion rate, agar plate set-up was used to observe the diffusion of different substances. The methylene blue and potassium permanganate (KMnO4) was used and placed in the plate. Because the two substances have distinct colors, the measurement of the diffusion zone was identifiable within the interval period of fifteen minutes and continues up to one hour. The diameter of the diffusion rate was measured every after fifteen minute interval of sixty minutes. The methylene blue which has the largest molecular weight had the slowest average diffusion rate of 0.02425 mm/min. compare to the KMnO4 which has the lightest molecular weight had a diffusion rate of 0.17425 mm/min. As obtained in the results of experiment, this satisfies the premise that the higher the molecular weight, the slower its diffusion rate.
The most common mechanism by which substances move in biological systems is diffusion. Diffusion in the most general state refers to the random, thermal motion of particles. It is a process in which there is a net movement of a substance from an area of higher concentration of that substance to an area of lower concentration. Diffusion occurs naturally, with the net movement of particles flowing from an area of high concentration to an area of low concentration. Net diffusion can be restated as the movement of particles along the concentration gradient. Although diffusion a very common in biological systems, it is also a very slow process. Diffusion in biology concerns the water environment themselves. The human body and some biological processes are examples. Taking for instance the digestion process wherein the chemically transformed food passes the intestinal wall into the bloodstream through diffusion. Molecules are in constant state of motion. The motion of these molecules is influenced by many factors. These factors are Kinetic Energy, Nature of Environment, and the Size of Molecules. Kinetic energy is the driving force which causes the molecules to move. Size of molecules, smaller molecules move faster than larger molecules. The greater the concentration of a substance in an area of a system entails that the frequency of particles colliding with each other is higher, causing the particles to “push” each other at a faster rate. These collisions are due to the high molecular velocities associated with the thermal energy “powering” the particles (Nave, 2008). At a given temperature, a smaller particle is said to diffuse at a faster rate than a larger one. This is because the larger the size of a particle, a greater amount of force is said to be required to move the particle (Meyertholen, 2007). With the same amount of energy, a smaller particle can be pushed faster than a larger particle. Thus, the hypothesis of the study is that the rate of diffusion is inversely proportional to the size of the particle. That is, a smaller particle will diffuse faster than a larger one. To test the hypothesis relating to the effect of molecular weight to the diffusion rate, agar plate set-up was used to observe the diffusion of different substances. The set-up involves drops of Methylene Blue and Potassium Permanganate...
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