Biology Prac1

Q4. The line should be a line of best fit. The line is in line of best fit is because it is only an estimation as there will be experimental errors which will affect the result of the experiment, line of best fit allows making predictions for future measurements.

Q5. No, it is not possible to determine the protein concentration of a solution from the standard curve if the measured absorbance is off the scale of the y-axis. This is because we may result in extrapolation which means we are predicting out of the standard curve’s line of best fit’s range. The standard curve is used to calculate the concentration of protein of an unknown solution by finding the protein concentration that corresponds to the absorbance reading obtained for that unknown solution as the concentration of protein is proportional to absorbance. However, it will be not proportional anymore to that of the concentration of the protein as all chemical reactions, it reaches a plateau.

PART 2

Q6. The concentration solution of silverbeet leaves that are grown in sun and shade cannot be determined from the standard curve as the concentrations are too high, it should be modified in this experiment in which the “sun”/”sh” labelled sample solution should be reduced to 0.25ml and diluted with 0.75ml of buffer solution so that the absorbance value lies within the range of the scale of the y-axis. However, the volume of biuret reagent must remain at 4ml so that the solution will totaled up to 5ml.

The concentration of BSA protein solution added to the test tubes that are labelled 1-6 should as well be modified by increasing its concentration as the amount of concentration of protein increases, the absorbance value will also increases. This will ensure that the absorbance value of the 6 test tubes increase hence increasing the range of absorbance value plotted in the standard curve.

Q7. Yes, my hypothesis is supported by my results as based on my results, the absorbance is proportional to the concentration of pigment in that solution. The absorbance is the amount of light absorbed by the coloured solution, hence, the higher the concentration of protein, the higher the absorbance as the more molecules to impede the photons will give a darker colour to the higher concentration of proteins. Furthermore, the absorbance reading for the test tubes labelled “Sun” has a higher absorbance reading than “Sh”, which is 0.411 and 0.351 respectively, as this is because RuBP Carboxylase (Rubisco enzyme) are usually higher when a plant is photosynthesizing rapidly.

Q8. The 1st possible error that may have occurred is the cuvette was not wiped with tissue properly before placing it into the spectrophotometer as our fingerprints and the water residues from rinsing the cuvette will affect the results as the light may be scattered or distracted. The 2nd possible error is the labels written on the test tubes are