Turn biological contexts into valid investigations by controlling variables, recording quantitative data clearly and judging conclusions against uncertainty and limitations.
Squid is an animal that is eaten in many parts of the world. The body of the squid is used as meat because it contains a lot of protein. The photograph shows some squid meat.
The meat from squid is quite tough and is often treated with enzymes to break down the protein. Some fruits contain enzymes that can break down protein. Pineapples contain the enzyme bromelain and unripe papayas contain the enzyme papain. A study compared the effects of two different concentrations of these two enzymes on the meat from squid. The flowchart shows some of the steps in the method used in this study.
Explain why, in step 1, it is important to cut the squid meat into equal sized pieces.
Name a suitable control solution that could be used in step 2.
State the importance of using a control in this study.
Give two variables that need to be controlled in step 3.
The graph shows the pH of the solutions measured at step 4.
The 0.001% enzyme solution was prepared by diluting the 0.004\% enzyme solution. Calculate the volume of the 0.004% enzyme solution needed to make of 0.001\% enzyme solution. Answer
State two conclusions that can be made from the data shown in the graph. (2)
Describe a method for estimating the soluble protein concentration in the beakers in step 4.
Flowering plants produce seeds that can be stored in a seed bank. This is done to conserve the biodiversity of plants.
The longer seeds are stored in seed banks, the less likely they are to germinate. This is due to ageing.
Ageing of seeds can affect the growth of roots when the seeds germinate.
Determining the mitotic index of roots is one way to study growth of roots.
Draw a table to show the data on the effect of root length on mitotic index in seeds treated for 14 days.
Identify the conclusions that can be drawn from these data.
The graph does not show the standard deviations of the means for mitotic index.
Describe how the investigation could be modified to allow standard deviations to be obtained.
The enzyme invertase breaks down sucrose into its two component monosaccharides.
The effect of pH on the initial rate of the reaction catalysed by invertase was investigated at .
State the independent variable in this investigation.
Name one non-biological (abiotic) variable, other than temperature, that should be kept constant in this investigation.
Describe how you would keep the variable you have named in (a)(iv) at a constant value.
The graph shows the results of this investigation.
Initial rate of reaction as a percentage of the maximum initial rate (\%)
Draw a suitable table to show these results.
Criticise the conclusion that 5.5 is the optimum pH for this enzyme.