The purpose of this experiment determined how temperature effects membrane integrity of living beet cells (Beta vulgaris). Beet cells possess a red pigment, betacyanin, located in the central vacuole and surrounded by tonoplast inside the plasma membrane of the cell. Disruption of these membranes results in betacyanin leaking through the vacuole and outside the cell. By subjecting beet cell membranes to a variation of temperatures, we may study the cellular function and structure through disruption and examine the overall effect on the cell (Lab 2 … 2018). The relevance is comparing plant cell function to human cell function.
Beet root discs were prepared using a razor blade to measure 5 mm; then rinsed in plastic beaker with lukewarm tap water for 10 minutes. With forceps, discs were subjected to various temperature treatments for two minutes and immediately placed in large test tubes with 10 mL of distilled water, vortexed, left to sit with two five-minute intervals where vortexed was repeated. Then, 5ml was pipetted into smaller test tubes and placed in spectrophotometer to measure the absorbance; the standard curve for betacyanin was used to determine the concentration. The control group was a beet disc placed immediately in test tube, as cells weren’t subjected to temperatures causing disruption to the membrane (Lab 2 … 2018).
The experiment resulted in higher absorbance’s towards the two extremes in comparison with the control group. The control group displayed an absorbance of 0.005 (A525) whereas, at 70°C the absorbance was 0.713(A525) and the absorbance at -5°C was 1.952 (A525). The intermediate treatment temperatures of 4°C, 40°C, and 50°C had an absorbance of, respectively, 0.044 (A525), 0.065(A525), and 0.050 (A525) (See Figure 2-2) (Lab 2 … 2018).
Cell membranes are composed of phospholipids and proteins. These phospholipids are arranged into bilayers due to the hydrophobic effect. The lateral movement of the phospholipids allows for proteins to interact and merge into the bilayer (Lab 2 … 2018). The high absorbance levels towards the two extremes (-5°C, and 70°C) indicate high concentrations of betacyanin leaked out of the cells. At high temperatures, the lateral movements of phospholipids increase. Also, proteins denature and unfold. Both creating openings in the membrane which allows betacyanin to leak. At freezing temperatures, the lateral movements of phospholipids decrease, creating more rigidity in the cell. Ice crystals form and spread, which pokes holes through the rigid membranes also causing betacyanin to leak out of the cell (Lab … 2018).
It’s suggested that temperature-induced structural changes in phospholipids rather than proteins are responsible for the loss of membrane integrity (Weiss, 1982). However, alternative opinions favour membrane protein denaturation (Levitt, 1980). Nevertheless, loss of membrane integrity results in a combination of phospholipids and proteins.
Beet discs for temperatures 4°C, 40°C, and 50°C were rinsed for 10 minutes. This results in a loss of betacyanin and explains the low absorbance’s. Especially since 40°C had an absorbance of 0.065(A525) and 50°C had an absorbance of 0.050 (A525). Also, the -5°C treatment went directly into the test tube which results in more betacyanin and explains the absorbance of 1.952 (A525). Therefore, improper methods were used as consistency was absent. Changes are recommended for more consistency, such as not rinsing discs. Following up this experiment with tests for ions which repair and aid against the disruption of membranes. (i.e. how calcium prohibits the discharge of betacyanin in beetroot discs when temperature increases (Cooke et al. 1986)). Applying these findings will deduce how human cells are damaged from fevers ultimately leading to medical improvement.