Experimental Laboratory Report:
An investigation into the rate of osmosis
Liana Gohery - 98332250
Word count - ………3000………..
This study was conducted to investigate the effect of concentration gradients on the rate of osmosis. Osmosis is the cellular transport of water, this study was conducted to show the significance of the rate at which this occurs. Dialysis bags were filled with three different concentrations of sucrose solutions and two with water. They were then completely immersed in water with the exception of one dialysis bag, which was filled with water and immersed in a sucrose solution. The weight of the bags were then monitored and recorded at regular 15-minute intervals. The variety of concentrations of sucrose created an area of low water potential compared to that of an area of high water potential, consequently creating a concentration gradient. The study showed that a greater concentration gradient, created by using the 60% sucrose solution immersed in water, showed a 28.1% increase in weight after 60 minutes whereas the bag filled with 40% sucrose solution showed an increase in weight of only 9.1% after 60 minutes. Thus confirming a direct correlation between the rate at which osmosis occurs and the concentration gradient present. 2. Introduction
Osmosis is a specialised form of cellular transport, which allows the diffusion of polarised water molecules to pass through the cell’s selectively permeable membrane down the concentration gradient until equilibrium is reached (Manson, 2005). The aims of this experiment were to specifically assess the activity of osmosis through a selectively permeable membrane and calculate the effects that different concentration gradients have on the rate activity occurring, using a method called dialysis tubing. Osmosis is a passive form of transportation as it requires no energy but a concentration gradient must be present between an area of high water potential and an area of low water potential. It is commonly defined as the net movement of water molecules through a cell membrane and plays a vital role in many bodily functions such as aiding digestion, filtration and maintaining homeostasis (REFERENCE). There are 3 types of environments that can exist to have an effect of the cells internal environment however all of these environments are relevant to the cells internal osmotic pressure. These 3 environments include: Hypertonic, where the external environment has a lower water concentration than the internal environment. Isotonic; this is where the osmotic pressure is equal in both the internal and external environments. Hypotonic; where there is a higher pressure of water in the external environment comparative to the pressure inside the cell. Due to the polarised nature of water molecules an isotonic environment is their preferred state (Campbell et al., 2008) The concentration gradient is said to have a direct effect on the rate at which osmosis occurs, the aims of this experiment were to establish the effect of the concentration gradient has on said rate and to understand why this is important to bodily processes. The hypothesised results were: (1) the bags full with the sucrose solutions would all increase in weight, with a correlation with regards to the intensity of the concentration gradient. (2) Over the given period of time the tap water filled dialysis bag immersed in 60% sucrose solution and the reverse experiment with the 60% sucrose filled dialysis bag immersed in tap water would display osmosis occurring at the same rate. (3) The Dialysis bag filled with tap water, immersed in tap water, would display no change in weight, as there is no concentration gradient. 3. Materials and Methods
The Materials and Methods were provided in the practical protocol. 4. RESULTS
Table 1 Displays the recorded results to the nearest 1st decimal place. Graph 1 displays the weights of each bag at each...
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