To better understand cell membranes and their interactions with the environment, we subjected beet cells to a range of 5 temperatures between -5°C and 70°C, to see at what point its membrane structure fails. Depending on the temperature, we are able to interpret the amount of betacyanin (beet pigment) leakage from the cell using a spectrophotometer to measure the amount of color emission. Therefore, if we freeze or heat beet root sections, we will see a higher concentration of betacyanin as there is a greater absorbency from the change in membrane permeability; allowing betacyanin to leak into the solution.
Looking at the reactions of the beet membrane not only demonstrates how cells function under stress, but lends to the importance of how our own cells are regulated. Similar to beets, human cells are composed of macromolecules such as proteins, carbohydrates and lipids and are what protect us against disease. Like farmers crops, we want to avoid cell denaturation in order to stay healthy and prosper.
Based on the instructions of Biology 107 Laboratory manual (2017-2018), a standard curve is made using 5 dilutions of varying ratios between distilled water and a 25 uM solution of betacyanin. Each dilution is measured by a spectrophotometer set at a wavelength of 525 nm and is calibrated on the created “blank” of distilled water. Once complete, the beet cells meet the temperature stress and each undergo a series of 2 min within the bath, 3 vortexes and 5 mL of solution extracted to be observed in the spectrophotometer.
Our control group was placing a dilution straight into the spectrophotometer without stress, since the room temperature is independent and does not rely on the manipulated variable.
As expected, our results for the extreme temperatures (-5°C and 70°C) shows the greater the absorption, the greater the concentration of betacyanin. Comparing the concentration of 4°C (1 uM) with that of 70°C (14 uM), it is clear that a warmer temperature increases the permeability of the beet cell and shows that there is a direct relationship between absorbance and concentration. Interestingly, despite the change in temperature between 4°C, 40°C and 50°C all of their absorptions as well as concentrations were the same. It is fair to say that beet root cells can withstand a range of cool to warm temperatures experiencing little to no damage. Also, seeing that the control group had a relatively low concentration of betacyanin is indicative of the relatively mild room temperature.
Looking at the fluid mosaic model, it is the fatty acids within the phospholipid bilayer that control permeability (Chandler 2017). When it gets too hot, there is an increase in fluidity and permeability. However, a cold environment will stiffen a cells membrane and decrease permeability. In fact, a research noticed by E. lbasyoni (2017), acknowledges that a dramatic increase or decrease in temperature will have a negative effect on plant membrane function. While their focus was on wheat and the detriments of drought on crops, the overall thermal findings are similar to our beet experiment.
Overall, there were not many problems regarding the procedure of the experiment. Being more accurate for the timing intervals and immediately placing the beet disk into test tubes could reduce any loss of heat/cold. If we were to further investigate membrane permeability, examining other species or adding different stresses (light, pressure, etc.) would be a better reflection of a true environment.