6 questions · 65 marks · ≈ 65 min · spans 6 of 8 topics
Assembled from the topic question banks — not an official Edexcel paperDescribe the structure of a protein such as an enzyme.
The mechanism of enzyme action is often described as being like a 'lock and key'.
Describe the mechanism of enzyme action.
During the digestive process, digestive enzymes break down larger molecules into smaller molecules.
Explain the role that digestive enzymes play in sustaining respiration in cells of the body.
The image below shows four specialised cells. Each cell is represented by a letter, A-D.
Identify one letter, from A-D, that corresponds to a cell that is described in each of the following statements. Each letter may be used once, more than once, or not at all.
(i) This is a plant cell.
(1 mark)
(ii) This cell contains digestive enzymes.
(1 mark)
(iii) This cell is motile (moves around).
(1 mark)
(iv) This cell is involved in co-ordination of the body's activities.
(1 mark)
Each of the cells shown in part (a) began its life as a stem cell.
Describe how a stem cell can give rise to the cell types shown in part (a).
Muscular dystrophy is a genetic condition in which patients lose muscle mass, leading to muscle weakness.
A clinical trial was carried out to investigate the effectiveness of bone marrow-derived stem cell treatment on muscle regeneration in muscular dystrophy patients.
(i) Bone marrow-derived stem cells are extracted from bone marrow.
Explain the abilities of stem cells taken from bone marrow.
(2 marks)
(ii) Suggest how stem cells could be used to treat muscle wasting.
(3 marks)
The graph below shows some of the results from the trial.
(i) Identify the dependent variable in this trial.
(1 mark)
(ii) Suggest how the researchers might have measured the dependent variable identified in part (i).
(2 marks)
(iii) Calculate the percentage of participants that showed a large muscle mass improvement in the trial. Give your answer to 1 decimal place.
(2 marks)
A medical student concluded from these results that stem cell therapy would be an effective treatment for muscular dystrophy.
Evaluate the student's conclusion.
The image shows the cross section of a leaf.
(i) Identify the cells labelled X and Y.
(2 marks)
(ii) Describe how the arrangement of cells such as Y help to maximise gas exchange in the leaf.
(2 marks)
Complete the table by adding an X to correctly identify the processes involved in controlling the opening and closing of the stomata.
| Water moves in to guard cells | Water moves out of guard cells | Cells become flaccid | Cells become turgid | |
|---|---|---|---|---|
| Stomata open | ||||
| Stomata close |
Explain why plants only absorb carbon dioxide during the day.
Some students set up an investigation into the effect of light on gas exchange in plants.They set up four boiling tubes as follows:
The students used hydrogen carbonate indicator to show the changes in carbon dioxide level for the four tubes over 30 minutes. Hydrogen carbonate indicator is an orange solution that turns yellow when carbon dioxide levels are high, and purple when carbon dioxide levels are low.
Explain the outcome that will be observed for the following:
(i) Tube B.
(2 marks)
(ii) Tube C.
(2 marks)
The image below shows the structure of a leaf in a green plant magnified 220 times.
For the image above:
(i) Name one type of organelle visible.
(1 mark)
(ii) Name two types of cell visible.
(2 marks)
(iii) Name two types of tissue present.
(2 marks)
Explain why the leaf shown in part (a) is an example of an organ.
The leaf image in part (a) measures 6 cm from top to bottom.
Use the formula below to calculate the actual thickness of the leaf. Give your answer in mm.
Pre-cut potato chips can be stored in salt solution before being cooked in restaurants. To avoid the chips becoming too salty, it is important to make sure that water does not move in or out of the chips as they are stored.
A scientist wanted to collect some data about the salt content of potato chips to inform the restaurants of the best storage concentration.
The steps in the table refer to the method that the scientist used to collect his results.
| 1 | Measure out 100ml of each salt solution into 5 different test tubes |
|---|---|
| Remove the chips, pat dry and reweigh | |
| Cut 5 potato chips of similar size and dimensions | |
| Place 1 chip into each concentration of salt solution and leave for 1 hour | |
| Record the mass of the potato chips |
Complete the table to place the steps in the correct order by adding numbers 2 to 5 into the left hand column of the table. The first stage has been labelled for you.
The graph shows the results obtained by the scientist when completing the investigation from part (a).
Identify the salt solution where the mass of the chip increases after one hour.
Explain what led to this increase in mass of the chip identified in part (b).
| A | Water moved out of the chip by osmosis |
|---|---|
| B | Salt moved into the chip by diffusion |
| C | Water moved into the chip by osmosis |
| D | The chip reacted with the salt in the solution |
The scientist concluded that the best solution for storing chips in would be 0.5 mol dm-3 salt solution because there would be no net (overall) movement of water into or out of the potato chips.
Suggest how the scientist can tell this from the results in the graph in part (b).
A student investigates the effect of light intensity on photosynthesis in leaf discs.
This is the student’s method.
The leaf discs rise in the solution due to the production of gas during photosynthesis.
The diagram shows some of the apparatus used.
Give the balanced chemical symbol equation for photosynthesis.
(i) State how the student could improve the reliability of their results.
(1 mark)
(ii) Give the dependent variable in the investigation.
(1 mark)
The graph shows the results of the investigation.
Explain the effect of increasing the distance of the lamp on the time taken for the leaf disc to rise to the top of the syringe.
Describe how the student could test the leaf discs for the presence of starch.