Movement of Materials Through Cell Membranes

Movement of Materials Through Cell Membranes - Movement of...

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Jenine Hajjar BI 101 Honors General Biology October 19, 2007 Abstract The purpose of this experiment was the observe diffusion of gases, molecules, and water. The lab also introduced the student to the use of dialysis bags and the necessity of a control group. The lab was split into three separate parts. The first part of the lab observed the diffusion of ammonium hydroxide and hydrochloric acid gases. The second part measured the distance molecules (dye samples) traveled in agar gel over a measured period of time. The second part had three parts in itself. Each part was started at different times and observed for one and one half hours. The third and final part of the lab observed the diffusion of water through a selectively permeable membrane, more commonly known as osmosis. Part one of the experiment showed the student the relationship between molecular weight and the rate of diffusion of gases. Part one displayed that gases with a smaller molecular weight will travel faster and farther than gases with a higher molecular weight. Part two showed the student the relationship between molecular weight and the rate of diffusion of particles. Four different dyes were used in this part of the experiment. The results suggest that the smaller the ~ 2 ~
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Finally, part three of the experiment displayed the relationship between the concentration of a solution and the rate of diffusion. This section of the experiment showed the student that the higher the concentration of a solution is, the faster it water will diffuse into the solution. Ultimately this experiment helped the student to see the different relationships between molecular weight/concentration and the rate of diffusion. It also revealed the significance of diffusion to the student, whether it be in plant cells or animal cells. Introduction “Gas and liquid molecules are always in motion” (Nelson 2004) and as they randomly move they have a tendency to spread out. This is more commonly known as diffusion. Diffusion is the net movement of substances from an area of higher concentration to an area of lower concentration (Pack 2001); however, there are multiple types of diffusion. Passive transport is the diffusion of a substance across a membrane (Campbell 2005). Another type of transport is active transport. Active transport is the movement of a substance across a membrane but it is against its concentration gradient, therefore requiring energy in order to occur (Campbell 2005). The type of diffusion that was dealt with in part 3 of this lab was osmosis. Osmosis is the diffusion of water molecules across a selectively permeable membrane. This differs from diffusion because osmosis is specifically the diffusion of water molecules. Osmosis is a type of diffusion. (Pack 2001). ~ 3
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Movement of Materials Through Cell Membranes - Movement of...

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