Match every method choice to validity, record raw and processed values with units and use repeats, variation and limitations to support or qualify conclusions.
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.
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.
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.
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 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.
The enzyme invertase breaks down sucrose into its two component monosaccharides.
The graph shows the results of this investigation.
Initial rate of reaction as a percentage of the maximum initial rate (\%)
Criticise the conclusion that 5.5 is the optimum pH for this enzyme.
Fibres from the stems of hemp plants are widely used in industry for their great tensile strength.
The relationship between tensile strength and fibre diameter was investigated.
The photograph shows a cross section of a part of a hemp fibre and an eyepiece graticule. The fibre bundle is made up of pith cells, some of which are shown here.
(Source: © Ted Kinsman/SCIENCE PHOTO LIBRARY)
The diagram shows apparatus that was used in an investigation to find the tensile strength of hemp fibres.
Some results from this investigation are shown in the table.
Plot a suitable graph of these results. Join the points with straight lines.
The effect of atropine and propranolol on heart rate was investigated.
One group of people, group 1, were given propranolol each day for four days followed by atropine for four days.
A second group of people, group 2, were given atropine each day for four days followed by propranolol for four days.
The graph shows the results of this investigation.
Mean heart rate/ beats
Calculate the change in mean heart rate for group 2 after 8 days.
Answer beats
The flow chart shows how garlic root tips can be treated to observe mitosis in the root cells.
Explain one safety precaution that must be taken when carrying out this procedure.
Carbohydrates are important molecules in living organisms.
The graph shows the relative sweetness of some monosaccharides and some disaccharides.
Devise an investigation that a student could carry out to confirm the data shown in the graph.
The enzyme invertase breaks down sucrose into its two component monosaccharides.
Describe how you would keep the variable you have named in (a)(iv) at a constant value.
Beetroot cells contain a red pigment called betalain. This pigment does not leak out of the cells, unless their membranes are damaged.
A student investigated the effect of detergent on beetroot cell membranes.
Discs of tissue were cut from a beetroot. Any betalain on the outside of the discs was removed.
One disc was placed into each of five test tubes, containing 0.2% detergent solution.
The five tubes were left for 30 minutes at .
The discs were then removed carefully.
Betalain had leaked from the discs and formed a red solution in each test tube.
Light was shone through this solution. The percentage of the light transmitted through the solution was recorded.
The same procedure was repeated using detergent concentrations of 0.0%,0.5%, 1.0% and 2.0%.
Explain why five discs were used for each concentration of detergent.
In an investigation, the water potential of a potato was compared with that of a yam.
The graph shows the results obtained in this investigation.
The equation for a straight line is y=mx+c.
Calculate m for the line of best fit for the potato data and write down the equation for this line.