Experiment+Report+A_Beetroot+cells+and+agar


 * Results:**

Exploration 4A-

temperature || 12-15 || slightly pink || 87.5 ||
 * Tube || Concentration of alcohol/% || Temperature of water/oc || No. of beetroot pieces || Colour || Conductivity I/O-1(mS) ||
 * A || 0 || room temperature || 3 || slightly pink || 96.5 ||
 * B || 25 || room temperature || 3 || pale pink || 90 ||
 * C || 50 || room temperature || 3 || reddish-pink || 56 ||
 * D || 0 || 90- 100 || 3 || slightly pink || 87.5 ||
 * E || 0 || room

Exploration 4B


 * No. of pieces of agar cubes || Length (cm) || Surface area (cm2) || Volume (cm3) || Surface area to volume ratio || Rate of conductivity change ||
 * 1 || 2 || 24 || 8 || 3:1 || 0.71 ||
 * 8 || 1 || 6 || 8 || 3:4 || 1.21 ||
 * 64 || 0.5 || 1.5 || 8 || 3:16 || 3.36 ||

**Analysis**

Diffusion is responsible for the reactions that were present in these two experiments. Diffusion is the spontaneous movement of a substance from high to low concentration. It is how many substances naturally move from where there is more to where there is less. This process can be seen in the experiment through the change of the rate of conductivity and the conductivity in the colorimeter.

For exploration 4A, pigments in the beetroot cells called betalain will move out of the cell into the liquid outside, which has a lower concentration through diffusion. With higher concentration of betalain, there will be a lower rate of conductivity in the colorimeter, which represents a higher rate of diffusion.

For exploration 4B, the bonds between the ions of the agar will be weaken and the ions will be free to move when it is dissolved. As the ions are small enough, they will diffuse out of the agar cube

into the surrounding water. The conductivity sensor is capable of monitoring the total concentration of ions in a solution. Hence, the higher the rate of conductivity, the higher the rate of diffusion.

The surface area to volume ratio can affect the rate of diffusion. This can be seen in both the experiments. In experiment 4A, tubes A and E can be compared to observe this. Tube A serves as a control for different setups. The beetroots pieces in have a greater surface area to volume ratio than Tube A as the same volume of beetroot is cut into smaller pieces. With a greater surface area to volume ratio, it has a greater rate of diffusion as shown in the lower rate of conductivity. In experiment 4B, the same volume of agar pieces cut into different number of cubes has different rate of diffusion. The rate of conductivity is 0.71 for 1 cube of agar, 1.21 for 8 cubes of agar and 3.36 for 64 pieces of agar. This shows that with a higher surface area to volume ratio, agar pieces will have a higher conductivity rate and hence a higher rate of diffusion.


 * Rate of Diffusion = surface area x concentration difference / distance**

The rate of diffusion depends on the beetroot cells or the agar blocks’ surface area that is in contact with the surroundings. With a larger surface area that is in contact with the surroundings, it has a larger “membrane” for the substances to be diffused to the outer surroundings, hence resulting in a higher rate of diffusion.

The concentration of the alcohol can also affect the rate of diffusion. This can be seen through the comparison of tubes A, B and C in the exploration 4A. Tube A with distilled water has a conductivity of 96.5, Tube B with 25% concentration of alcohol has a conductivity of 90 and Tube C with 50% concentration of alcohol has a conductivity of 56. This shows that with a higher concentration of alcohol, the lower the rate of conductivity, the higher the rate of diffusion.

The alcohol is able to break down the cell membrane of the beetroot cells. The pigment, betalain, is found within the vacuole of the beetroot cell. When the cell membrane is broken down, the permeability of the cell will increase, hence betalain will be able to diffuse into the outer surroundings in a faster rate. Hence, with a higher concentration of alcohol, there will higher rate of diffusion.

The water concentration can also affect the rate of diffusion. This can be observed through the comparison of tubes A and D in the experiment 4A. Tube A with water at room temperature has a conductivity of 96.5 while Tube D with water of temperature 90 - 100 degree celsius has a conductivity of 87.5. With a higher water temperature, there will be a increase of rate of diffusion as shown in the decrease in the conductivity.

The increased temperature of water has the same effect as the high concentration of alcohol. Increased water temperature is also able to break down the cell membrane of the beetroot cell, causing the increase of the permeability of the cell, hence, the pigments in the cells, betalain, will be better able to diffuse into the other surroundings in a faster rate. Hence, in conclusion, increased temperature will cause an increase in the rate of diffusion.


 * Conclusion**


 * The greater the surface area to volume ratio, the higher the rate of diffusion.
 * The higher the concentration of alcohol, the higher the rate of diffusion.
 * The higher the water temperature, the higher the rate of diffusion.


 * Precautions**

For experiment 4A
 * Wash the beetroot slices thoroughly before using them for the exploration - This is because after cutting the beetroot into slices, the cell membrane will be broken and betalain will leak out of the beetroot. Hence, it is important to wash them before the experiment so that the extra betalain will not result in errors during the experiment.
 * Extract liquid from all the test tubes after the 15minutes to ensure precision.

For experiment 4B
 * Cut the 3 pieces of solid agar into 2 x 2 x 2 cm3 to ensure the same volume before cutting them into smaller pieces.
 * Stop the experiment slightly after 2 minutes to ensure precision.

**Errors**

For experiment 4A
 * We might not have washed the beetroot thoroughly enough and hence causing some imprecision
 * We might not have adjusted the screen to register exactly 100%
 * The period of the beetroot slices immerged in the liquid might not be the same for all the 5 tubes

For experiment 4B
 * The 3 solid cubes might not have the exactly same volume at first
 * While stirring, the stirring rod might be lifted out of the solution at times.

Application

This concept of diffusion can also be applied to organisms. Organisms need to exchange heat with their surroundings, and hence large animals, such as tigers, have an advantage in having a small surface area/volume ratio as they lose less heat than small animals, such as earthworms. Hence, large animals keep warm quite easily and don't need much insulation or heat generation.

Diffusion also applies to cells. As organisms get bigger their surface area/volume ratio gets smaller. This means that as organisms become bigger it becomes more difficult for them to exchange materials with their surroundings. This problem causes the maximum size for a single cell to be around 100 mm. In anything larger than this, substances simply cannot diffuse fast enough to support the reactions needed for life. Very large cells are mostly inert food storage with a thin layer of living cytoplasm round the outside.