draft.pdf

Questions Q1. Answer the questions with a cross in the box you think is correct. If you change your mind about an answer, put a line through the box and then mark your new answer with a cross. The diagram shows a bacterium with structures A, B, C, D and E labelled. (a) (i) Which structure co...

Questions Q1. Answer the questions with a cross in the box you think is correct. If you change your mind about an answer, put a line through the box and then mark your new answer with a cross. The diagram shows a bacterium with structures A, B, C, D and E labelled. (a) (i) Which structure contains the genetic material used by the bacterium in reproduction? (1) A B C D (ii) Which structure controls the substances entering and leaving the bacterium? (1) A  B D E (b) Give three differences between the structure of this bacterium and the structure of a plant cell. (3) 1.................................................................................................................................................................................................................................................................................................................................................................................................................................... 2.................................................................................................................................................................................................................................................................................................................................................................................................................................... 3.................................................................................................................................................................................................................................................................................................................................................................................................................................... (Total for question = 5 marks) (Q01 4SS0/1B, June 2022) Q2. The diagram shows a cell found in the lining of the human small intestine. (a) (i) Which of the labelled structures is a microvillus? (1) A B C D (ii) Which of the labelled structures produces ATP? (1) A B C D (b) These cells form the lining of the small intestine. Explain how the structure of the small intestine is adapted for absorption. (4)............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (c) Cells in the human placenta also have microvilli. Describe the role of the human placenta. (3)..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (Total for question = 9 marks) (Q03 4BI1/2BR, June 2022) Q3. The diagram shows a single-celled organism called Chlorella that lives in fresh water. Chlorella has a chloroplast and can photosynthesise. (a) (i) Which of these groups of organisms contains Chlorella? (1) A animals B bacteria C plants D protoctists (ii) Which of these labelled structures would also be present in an animal cell? (1) A cell membrane and chloroplast B cell membrane and mitochondrion C cell wall and chloroplast D cell wall and mitochondrion (b) Complete the balanced chemical symbol equation for photosynthesis. (2).............................................................. +............................................................................................................................ + 6O2 (c) The graph shows the effect of light intensity on gas exchange by Chlorella. (i) Explain why Chlorella takes in oxygen at light intensities below 10 arbitrary units. (2).................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (ii) Explain the changes in the volume of oxygen released as the light intensity increases from 10 arbitrary units. (3).............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. (iii) The volume of oxygen released by Chlorella is the difference between the oxygen produced by photosynthesis and the oxygen taken in. Use the graph to calculate the volume of oxygen produced in five minutes by photosynthesis at a light intensity of 50 arbitrary units. (2) volume of oxygen =.................................................................. mm3 (d) Describe how hydrogen-carbonate indicator could be used to investigate the effect of light intensity on carbon dioxide exchange by Chlorella. (3).............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. (Total for question = 14 marks) (Q03 4BI1/2B, June 2022) Q4. Biologists classify organisms into different groups. Two of these groups are bacteria and fungi. (a) Complete the passage about bacteria by writing a suitable word or words in each blank space. (8) Bacteria are small.............................................................. celled organisms. They have a cell membrane and a cell.............................................................. , made of peptidoglycan. Some bacteria are able to use the energy from the Sun to carry out.............................................................. but other bacteria are.............................................................. and feed on dead and decaying organisms. Bacterial cells do not have a nucleus but most of their genetic material is contained in a circular.............................................................. of DNA. They also have small circles of DNA called.............................................................. in their cytoplasm. Some bacteria are used by humans in food production. An example is using.............................................................. to make yoghurt. Other bacteria, such as Pneumococcus, cause disease and so are called............................................................... (b) A microscopic single-celled fungus, yeast, is used in the production of bread. Describe how yeast is used to produce bread. (4)............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ (Total for question = 12 marks)  (Q07 4BI1/1B, Nov 2023) Q5. The bacterium H. pylori causes stomach ulcers. (a) The diagram shows this bacterium. (i) Which of these is found in this bacterium? (1) A cellulose B chitin C cytoplasm D nucleus (ii) The bacterium has evolved to release an enzyme called urease. The action of the bacterium neutralises the acid in the stomach. What is the pH changed to? (1) A 1 B 2 C 7 D 12 (iii) Use the theory of evolution by natural selection to explain how H. pylori bacteria could have evolved to produce urease. (4)............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ (b) Probiotics are live microorganisms that can have health benefits when consumed. Scientists investigate the ability of probiotics and cranberry juice to reduce the growth of H. pylori. The scientists give various treatments to a group of people who have H. pylori. The treatments are given daily for three weeks. The scientists measure the mean percentage reduction of H. pylori for each treatment. The table shows the scientists' results. Give two conclusions from these results. (2) 1.......................................................................................................................................... 2..........................................................................................................................................  (Total for question = 8 marks) (Q01 4BI1/1B, Nov 2020) Q6. Beta thalassaemia is a genetic condition caused by a mutation in a gene for haemoglobin. People with beta thalassaemia produce less haemoglobin and fewer red blood cells than people without the condition. (a) Explain why people with beta thalassaemia may experience severe tiredness. (2).............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. (b) A new treatment for beta thalassaemia has been developed that edits the haemoglobin gene. These are the steps in the treatment. remove blood stem cells from a patient's bone marrow put a strand of RNA and an enzyme into the blood stem cells to correct the haemoglobin gene use drugs to destroy the patient's remaining bone marrow cells replace the patient's bone marrow cells with the modified stem cells The modified stem cells that are in the bone marrow now produce red blood cells containing sufficient haemoglobin. (i) The strand of RNA used in this treatment is complementary to one strand of the DNA in the haemoglobin gene. Give the base sequence of RNA that is complementary to this sequence of DNA. (2) DNA strand RNA strand............................................................................................................................................. (ii) Protein synthesis of the modified gene will produce haemoglobin. Describe the stages of this protein synthesis. (4)............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ (iii) The standard treatment for beta thalassaemia is a weekly blood transfusion. The new treatment has so far been tested on two patients, with these results. both patients started making large numbers of red blood cells with sufficient haemoglobin both patients experienced serious side effects from the drugs used, needing to spend several months in isolation in hospital before recovering 15 months after the treatment, neither patient required further blood transfusions both patients were able to exercise normally without feeling tired Evaluate the use of the new treatment compared to weekly blood transfusions. (4)......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (Total for question = 12 marks) (Q06 4BI1/2B, June 2022) Q7. As an embryo develops, its cells differentiate. (a) Explain the importance of cell differentiation in the development of the growing embryo. (2).................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (b) (i) Which of these is a feature of adult stem cells? (1) A they do not divide B they divide by meiosis C they can become all cell types  D they are found in some tissues and organs (ii) Adult stem cells or embryonic stem cells can be used in medical treatments. Explain why the choice between these two types of stem cells can cause issues for doctors. (2).................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (Total for question = 5 marks) (Q07 4BI1/2B, Nov 2021) Q8. All living organisms have certain characteristics. (a) Describe what is meant by the following characteristics: (i) respiration (2).................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (ii) control of their internal conditions (2).................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (b) Organisms are organised into different levels. What is the correct order of the levels? (1) A organ, system, tissue, cell, organelle B organ, tissue, cell, system, organelle C organelle, cell, tissue, organ, system D system, cell, organelle, organ, tissue (c) Yeast is an example of which group of organism? (1) A animals B bacteria C fungi D protoctists (Total for question = 6 marks) (Q01 4SS0/1B, SAM 0) Q9. Answer the questions with a cross in the boxes you think are correct. If you change your mind about an answer, put a line through the box and then mark your new answer with a cross. Plant cells contain organelles. The diagram shows a plant cell containing some organelles. (a) (i) What is the total number of organelles shown in the diagram that absorb light? (1) A 1 B 6 C 11 D 12 (ii) Name an organelle not shown in the diagram that makes ATP. (1)............................................................................................................................................. (b) The magnification of the cell is calculated using this formula. The actual width of the cell is 40 μm. The magnification of the plant cell is (1) A ×0.06 B ×0.6 C ×6 D ×600 (c) (i) Name an organelle found in a plant cell but not found in an animal cell. (1)............................................................................................................................................. (ii) The location of the genetic material in a bacterium is different from the location of the genetic material in a plant cell. Give a location in a bacterium where genetic material is found. (1)............................................................................................................................................. (Total for question = 5 marks) (Q01 4SS0/1B, June 2019) Q10. Organisms can be classified into groups based on their features. (a) State three differences between eukaryotic and prokaryotic organisms. (3) 1....................................................................................................................................................................................................................................................................................... 2....................................................................................................................................................................................................................................................................................... 3....................................................................................................................................................................................................................................................................................... (b) Give an example of a disease caused by a protoctist. (2) name of protoctist............................................................................................................................................. name of disease............................................................................................................................................. (Total for question = 5 marks)  (Q02 4BI1/1B, Jan 2020) Q11. Answer the questions with a cross in the boxes you think are correct. If you change your mind about an answer, put a line through the box and then mark your new answer with a cross. Living organisms share a number of characteristics. (a) State two of the characteristics shared by living organisms. (2) 1.......................................................................................................................................... 2.......................................................................................................................................... (b) Organisms are classified into different groups based on their features. (i) Which feature is found in fungi? (1) A chloroplast B cellulose cell wall C hypha D plasmid (ii) Which organism is classified as a fungus? (1) A amoeba B chlorella C mucor D plasmodium (c) Viruses are not classified as living organisms. Explain one reason why viruses are not classified as living organisms.  (2)................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. (Total for question = 6 marks) (Q01 4SS0/1B, June 2023) Q12. (a) All living organisms share characteristics. (i) State two characteristics that all living organisms share. (2) 1....................................................................................................................................................................................................................................................................................... 2.......................................................................................................................................... (ii) Some organisms are pathogens. Which of these organisms can cause a bacterial disease in humans? (1) A Chlorella B Lactobacillus bulgaricus C Mucor D Pneumococcus (b) Viruses are pathogens but not living organisms. (i) Describe the effect of a named virus that infects plants. (2).................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (ii) Give three differences between the structure of viruses and bacteria. (3) 1....................................................................................................................................................................................................................................................................................... 2....................................................................................................................................................................................................................................................................................... 3....................................................................................................................................................................................................................................................................................... (Total for question = 8 marks) (Q01 4BI1/1B, June 2023) Q13. The diagram shows a plant cell with some structures labelled. (a) (i) Which structure is the cell vacuole? (1) A P B R C S D T (ii) Which structure is the site of photosynthesis? (1) A P B Q C R D T (iii) Which structure is the cell wall? (1) A P B Q C S D T (iv) Structure U is the site of protein synthesis in the cell. What is the name of structure U? (1) A chloroplast B mitochondrion C ribosome D starch granule (b) A cell is shaped like a cube. Each side has a length of 0.053 mm. Calculate the surface area to volume ratio of this cell. Give your answer in the form n : 1 (3) surface area to volume ratio =............................................................ : 1 (c) Animal cells, unlike plant cells, do not have a cell wall. (i) Explain how this difference affects red blood cells when placed in distilled water. (3)........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ (ii) Explain how this difference affects red blood cells when placed in a concentrated salt solution. (2).............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. (Total for question = 12 marks) (Q03 4BI1/1B, June 2023) Q14. (a) Describe how stem cells are different from other cell types. (2).................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (b) Stem cells from a donor can be used for stem cell therapy. Human blood cells are produced in bone marrow. Explain how using stem cells from the bone marrow enables doctors to treat a number of different blood conditions. (3)..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (c) One type of stem cell transplant uses a patient's own stem cells. They can be used if the patient is producing enough healthy bone marrow cells. These cells can be collected, frozen and stored for later use. Explain the advantage of using the patient's own stem cells rather than using stem cells from a donor. (2)........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ (Total for question = 7 marks) (Q06 4BI1/2B, Nov 2023) Q15. P. multocida is a bacterium that causes cholera in chickens. The diagram shows the bacterium. (a) Give two structures in this bacterium that are also found in all eukaryotic cells. (2) 1.......................................................................................................................................... 2.......................................................................................................................................... (b) Scientists investigated the survival of chickens injected with normal P. multocida or with weakened P. multocida. The table shows the scientists' results. (i) What is a correct conclusion about P. multocida from these results? (1) A they are decomposers B they are pathogens C they are microscopic D they are non-living (ii) The scientists took the living chickens that had been injected with weakened P. multocida and then injected them with normal P. multocida. The chickens did not die, as they were now immune. Explain why these chickens did not die. (4)............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ (Total for question = 7 marks) (Q02 4BI1/2B, June 2021) Q16. All living organisms have certain characteristics. (a) Describe what is meant by the following characteristics: (i) respiration (2).................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (ii) control of their internal conditions (2).................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (b) Organisms are organised into different levels. What is the correct order of the levels? (1) A organ, system, tissue, cell, organelle B organ, tissue, cell, system, organelle C organelle, cell, tissue, organ, system D system, cell, organelle, organ, tissue (c) Yeast is an example of which group of organism? (1) A animals B bacteria C fungi D protoctists (Total for question = 6 marks) (Q01 4SS0/1B, SAM 0) Examiner's Report Q1. (b) This question required candidates to give three differences between the structure of the bacterium shown in the diagram and the structure of a plant cell. Most candidates were able to score some marks, with the best responses giving three differences. Results Plus: Examiner Comments This response gains all three marks for three correct differences. Results Plus: Examiner Tip Candidates should make it clear which organism they are writing about. In this case it is the bacterium. This response scores two marks for two correct differences. Results Plus: Examiner Comments The second difference is incorrect as the bacterium also has a cell wall. Q2. (b) See below. Results Plus: Examiner Comments This answer scores four marks for describing the wall of the villi as one cell thick for faster diffusion, villi and microvilli to increase surface area, and capillaries to carry away substances maintaining diffusion gradient. Results Plus: Examiner Comments This response also scores four marks for describing how villi and microvilli increase the surface area, capillaries to maintain the diffusion gradient, lacteals to absorb triglycerides, and the villi walls are only one cell thick minimising diffusion distance. Results Plus: Examiner Tip This response gives each structure and explains how they improve absorption. (c) In this item students were asked to describe the role of the human placenta. Most responses were able to describe how the foetus receives glucose or amino acids from the placenta and the placenta removes waste products such as urea and carbon dioxide from the foetus. The better responses also described how the placenta provides oxygen from the mother to the foetus. Results Plus: Examiner Comments This response gains all three marks for describing the passage of oxygen and glucose from the mother to the foetus and the removal of carbon dioxide and urea from the foetus to the mother. Results Plus: Examiner Comments This response scores two marks for the passage of oxygen and nutrients from the mother to the foetus. Q3. (b) Most candidates were able to complete the balanced chemical symbol equation. A few candidates confused the equation for photosynthesis with the equation for respiration. Some candidates were unable to balance the equation and a few were not aware of the chemical formula for glucose. Results Plus: Examiner Comments This answer gained one mark for correctly giving the left hand side of the equation. The candidate has given the incorrect formula for glucose. Results Plus: Examiner Comments This answer gained two marks. The candidate has completed both sides of the equation correctly. (c)(i) This question assessed candidates' knowledge of gas exchange in plants. Many candidates correctly recognised that at low light intensities the rate of respiration was higher than the rate of photosynthesis resulting in a net intake of oxygen. Some candidates recognised that the photosynthesis rate would be low but did not relate this to the rate of respiration. Candidates should make sure that they explain data fully. Results Plus: Examiner Comments This answer gained two marks. The candidate explains that the light intensity is low and so the rate of photosynthesis is lower than the rate of respiration. Results Plus: Examiner Comments This answer gained no marks. The candidate has not referred to how the low light intensity has affected the rate of photosynthesis. Results Plus: Examiner Comments This answer gained two marks. The candidate has correctly explained that the rate of photosynthesis is higher than the rate of respiration so that the rate of oxygen consumption is higher than the rate of oxygen production. (ii) This question required candidates to look at the effect of increasing light intensity on the rate of oxygen production. Candidates had to recognise that increasing the light intensity increased the rate of photosynthesis until other factors limited the rate. Many candidate scored at least one mark but few went on to gain all three. A significant number of candidates recognised that other factors would limit the rate of photosynthesis beyond 55 arbitrary units of light but a few incorrectly stated that light would be limiting at that light intensity. A few candidates correctly stated that at 10 arbitrary units the rates of photosynthesis and respiration were equal. Some candidates did not give explanations but instead gave descriptions of the data. Results Plus: Examiner Comments This answer did not gain any marks. The candidate has given a description rather than giving an explanation. Results Plus: Examiner Tip Always read command words carefully. Do not confuse 'describe' with 'explain'. Results Plus: Examiner Comments This answer gained all three marks. The candidate has correctly stated that the rate of photosynthesis has increased and related this to the rate of respiration. The candidate also goes on to explain that other factors limit the rate of photosynthesis at 55 a.u. Results Plus: Examiner Comments This excellent answer gained all three marks. The candidate correctly states that the rate of photosynthesis increases and becomes higher than the rate of respiration. The candidate also goes on to explain the changes in oxygen release and the effect of other limiting factors. (iii) Many candidates found this question challenging. Candidates were asked to use the graph to calculate the volume of oxygen produced by photosynthesis. Candidates were required to use the graph to determine the volume of oxygen used by respiration at zero light intensity and add this to the net volume of oxygen released at 50 a.u. Many candidates were able to determine the volume of oxygen released at 50 a.u. but only a few were able to use this to correctly calculate the total volume of oxygen produced. Results Plus: Examiner Comments This answer gained both marks for correctly calculating the volume of oxygen produced. Results Plus: Examiner Comments This answer gained one mark for correctly using the graph to determine the volume of oxygen released. The candidate has incorrectly subtracted the volume of oxygen used by respiration. (d) This question asked candidates to describe how the hydrogen-carbonate indicator could be used to investigate the effect of light intensity on gas exchange. Some excellent answers were seen that explained how light intensity could be changed, often by placing a lamp at different distances. A significant number of candidates did not give a method for changing the light intensity but simply stated that the light intensity would be changed. Many candidates correctly explained the colour changes that occur when carbon dioxide increases and decreases. Some candidates incorrectly referred to oxygen changing the colour of the indicator and some gave incorrect colour changes. Many candidates correctly stated that a control tube with no Chlorella would be used and others gave correct control variables. Candidates should be careful to refer to volumes rather than amounts, for example, they should state that the same volume of indicator is used. Results Plus: Examiner Comments This answer gained one mark for the correct colour changes. No method for changing the light intensity was given. Results Plus: Examiner Comments This answer gained all three marks. The candidate has correctly given a method for changing the light intensity, has controlled the time taken and has given correct colour changes. Results Plus: Examiner Tip Make sure that practical details are given. For example, state how the light intensity would be changed rather than just stating that it will be changed. Q4. (a) This question gave students a passage about bacteria to complete. Most responses gained at least 4 marks with many gaining full credit. The words that most students failed to get were chromosome and pathogen. In part (b) students had to describe how yeast is used to produce bread. Again many scored 3 or 4 marks for describing how aerobic then anaerobic respiration by yeast releases carbon dioxide which inflates the dough. Only the best responses included the role of amylase in converting starch to maltose. Q5. This question provided students with a diagram of a bacterium H. pylori that causes stomach ulcers. In part (a)(i) most could successfully identify that cytoplasm is found in the bacterium. In (a)(ii) most students could identify the pH that is produced when stomach acid is neutralised. In (a)(iii), students were asked to use the theory of evolution by natural selection to explain how H. pylori bacteria could have evolved to produce urease. Many students were able to correctly explain that there would be variation in a population of bacteria and that a mutation might lead to urease production, these bacteria would be more likely to survive in stomach acid so reproduce passing on the allele for urease production. Some students wrote about the phenotype being passed on rather than the allele. In (b), students were given data about the ability of probiotics and cranberry juice to reduce the growth of H. pylori. They were required to give two conclusions from the results. Most answers gained credit with the best responses concluding that the cranberry juice and probiotics reduced growth of the bacteria and that both treatments used together were the most effective. Q6. This question was well answered by many candidates. Most appreciated that having less haemoglobin would reduce the oxygen transported and many candidates went on to explain that this would reduce the respiration rate of body tissues. Many also correctly stated that there would be less oxygen transported to the muscles although a significant number simply stated that less oxygen would be transported to the body. Candidates should always try to refer to the affected structures, organs and tissues. Some candidates gave vague references to reduced transport of energy – candidates should always refer to transport of oxygen when discussing haemoglobin. Results Plus: Examiner Comments This answer was awarded one mark for correctly stating that less oxygen would be transported. No second mark was awarded as there was no reference to muscles or respiration. Results Plus: Examiner Comments This answer was awarded one mark for stating that less oxygen is transported. There is no mention of respiration or muscles. Results Plus: Examiner Comments This excellent answer gained two marks. The candidate correctly refers to the reduced transport of oxygen and goes on to explain that there would be less respiration. (b)(i) This question was well answered with many candidates gaining both marks. Most understood the base pair rule and that RNA contains uracil rather than thymine. A few candidates did not replace thymine with uracil and so gained one mark. Results Plus: Examiner Comments This correct answer gained two marks. The candidate has shown the correct base pairing and recognised that U replaces T. Results Plus: Examiner Comments This answer was given one mark. The base pairing is correct but the candidate has not replaced T with U. (ii) This question generated a wide range of responses. Many outstandingly accurate and detailed answers that gained full marks were seen. A significant number of answers contained detail of an A level standard that went well beyond the requirements of the International GCSE specification. Many candidates wrote well organised descriptions of 'transcription' and 'translation' using technical terms such as 'codons' and 'anticodons'. Some candidates were aware of the terminology involved in protein synthesis but did not use it accurately. For example, transcription and translation were sometimes confused. Some candidates did not state that mRNA and tRNA are involved and just referred to RNA production. Another common error was the suggestion that the RNA is made from amino acids rather than tRNA bringing amino acids to be joined together. A few candidates left the answer blank or gave vague references to ribosomes being involved in protein synthesis. In the specification, this topic is printed in bold and so can only be tested on paper 2 – candidates should ensure that they pay particular attention to emboldened topics before taking paper 2. Results Plus: Examiner Comments This answer did not gain any marks. Messenger RNA is mentioned but there is no clear indication that it has been produced from the DNA template. Results Plus: Examiner Comments This is an excellent answer that gained all four marks. The candidate gives a detailed, logical account of 'transcription' and 'translation' using all technical terms accurately. Results Plus: Examiner Comments This is an excellent answer that gained all four marks. All mark points are present. (iii) This question required candidates to read the information about the use of genetic modification to treat thalassaemia and evaluate whether or not it is a better treatment than using blood transfusions. Most candidates scored at least two marks with many going on to gain three or four. Many candidates recognised that the new treatment was permanent, increased the number of red blood cells and reduced the need to keep attending hospitals. Most candidates also recognised that there were downsides to the new treatment such as the side effects, small sample size and time scale of the trial and the need to spend time in isolation. The examiners all commented on how well most candidates had answered the question - most candidates gave both sides of the argument and considered several points. Candidates have worked hard since the last series to improve their answers to these longer style questions. Results Plus: Examiner Comments This answer was awarded two marks. The candidate has stated that the new treatment has side effects but reduces the long-time dependence on hospitals. Results Plus: Examiner Tip If asked to evaluate information, make sure that both sides of the argument are considered. Results Plus: Examiner Comments This excellent answer was awarded four marks. The candidate states that the benefits of the new treatment include the fact that more red blood cells are made, there is no risk of rejection, and there are fewer hospital visits needed. They also give negative aspects of the treatment such as the side effects and the fact that there is only a small sample size. Results Plus: Examiner Comments This answer gained all four marks. Both benefits and drawbacks of the new treatment are considered. Q7. (a) Many students were able to correctly state that cells in an embryo specialise so that the cells have different functions. Many went on to state that these cells are part of the organs and tissues of the embryo. Many students gained at least one mark, usually for the idea of cell specialisation. (b)(i) This multiple-choice question tested students' understanding of the nature of adult stem cells. Many correctly recognised that adult stem cells are found in some cells and organs. (ii) Many students gained at least one mark for this question. Many recognised that the use of embryonic stem cells brings ethical issues. Many also recognised that although adult stem cells have fewer ethical issues, they are more limited in the number of cell types that they produce. Where students only gained one mark, it was typically for only considering one type of cell. Q8. No Examiner's Report available for this question Q9. In this question students were given a diagram of a plant cell. In (a) (ii) most responses correctly identified the organelle that makes ATP as a mitochondrion. In item (c) (i) most students could name an organelle found in plant cells but not in animal cells. Students should note that the cell wall is not an organelle. In item (c) (ii) most responses did not correctly give a location for genetic materlal in a bacterium. Suitable correct answers given included plasmid, cytoplasm and a circular chromosome. Q10. This question examined candidates' knowledge and understanding of the structure of eukaryotic and prokaryotic organisms. In (a) candidates were asked to state three differences between eukaryotic and prokaryotic organisms. Many candidates did not recognise the terms, although they are clearly stated in sections 1.2 and 1.3 of the specification. This led to disappointing scores with few responses gaining credit and only the very best gaining all three marks. The best students were able to state that eukaryotic organisms have a nucleus, have organelles, have chromosomes and lack plasmids. Candidates did better in part (b) with about half of responses gaining some credit and the best naming the protoctist as plasmodium that causes malaria. Other correct examples were credited but malaria caused by a plasmodium is clearly stated in the specification. Q11. (a) most candidates were able to state two of the characteristics shared by living organisms. Most common answers were reproduction and respiration. Some weaker responses wrote about having cell structures. Results Plus: Examiner Comments This response scores both marks for reference to movement and growth. Results Plus: Examiner Comments This response also gains both marks for growth and reproduction. Results Plus: Examiner Comments This response also gains both marks for respiration and growth. (c) asked candidates to explain one reason why viruses are not classified as living organisms. Many candidates gained at least one mark, with the best responses explaining that viruses do not show the characteristics of living organisms such as respiration or growth. Others gained both marks for explaining that viruses can only reproduce inside a host cell. Results Plus: Examiner Comments This response gains both marks for explaining that a virus can only reproduce using a host cell. Results Plus: Examiner Comments This response also gains both marks for explaining that a virus can only reproduce using a host. Results Plus: Examiner Comments This gains one mark for explaining that viruses do not have the characteristics of living organisms. Results Plus: Examiner Tip If the response had given a suitable example such as growth it would have gained the second mark. Q12. (a)(i) (a)(i) required candidates to state two characteristics that all living organisms share. Most responses gained both marks using a variety of different characteristics. Results Plus: Examiner Comments This response scores both marks for referring to movement and to excretion. Results Plus: Examiner Tip Always write each answer on the numbered lines, don't be tempted to include more than the number asked for. Results Plus: Examiner Comments Movement and reproduction are also suitable characteristics. So this example also gains both marks. Results Plus: Examiner Comments This example also gains two marks. (b)(i) (b)(i) required candidates to describe the effect of a named virus that infects plants. Those candidates that were familiar with the specification content were able to name the tobacco mosaic virus and describe how it leads to yellow leaves or leaves with white spots due to lack of chlorophyll. Results Plus: Examiner Comments This example gains both marks as it correctly names the tobacco mosaic virus and describes its effect as leaves without green colour and less photosynthesis. Results Plus: Examiner Tip Ensure that you are familiar with all the specification content. Results Plus: Examiner Comments This answer also names the virus and correctly describes its effects. There is no penalty for a slight spelling error of mosaic. Results Plus: Examiner Comments This response gains no credit as it does not name a virus. Mucor is a fungus. (b)(ii) (b)(ii) asked candidates to give three differences between the structure of viruses and bacteria. The answer lines were numbered so that candidates could write one difference on each line. Results Plus: Examiner Comments This response gains all three marks for correctly stating that viruses have a protein coat, that bacteria have a cell wall and that bacteria have cytoplasm. Results Plus: Examiner Tip Some responses did not write about structure. Make sure to read the question carefully. Results Plus: Examiner Comments This response also gains three marks for bacteria have plasmids, viruses have a protein coat and bacteria have a cell wall. Results Plus: Examiner Comments This response gains two marks for bacteria have plasmids and bacteria have a cell wall. Results Plus: Examiner Comments This response scores two marks. Bacteria have cell walls and viruses have a protein coat. No credit for carry out respiration as it is not a structural difference. Results Plus: Examiner Tip This question asked for differences in structure so no credit for differences in function. Q13. (b) (b) required candidates to calculate the surface area to volume ratio of a cell shaped like a cube. The mathematics skills given in the specification include calculation of surface area and volume of regular shapes such as a cube. Many responses gained all three marks however those that did not could still gain credit if some of their working was correct. Results Plus: Examiner Comments This response scores all three marks for a correct answer of 113.2. Results Plus: Examiner Comments This response also scores three marks for a correct answer of 113. Results Plus: Examiner Comments This response fails to get the correct answer. However it gains 2 marks for correctly calculating the surface area as 0.0168 and for calculating the volume as 1.48877 ×10 –4. (c)(i) (c) told candidates that red blood cells do not have cell walls. They then had to explain how this difference would affect red cells when placed in distilled water. Most candidates were able to score three marks. Those responses that did not gain marks were confused about the direction of water movement in osmosis. The best way for candidates to explain osmosis is the movement of water from a dilute solution to a more concentrated solution. Some candidates explained osmosis in terms of water moving from a region of higher water potential to a region of lower water potential and that is also fine and a good preparation for A level terminology. Describing water as being more concentrated or less concentrated is confusing. Results Plus: Examiner Comments This response scores full marks as it refers to the cell bursting, water enters by osmosis due to a lower water potential inside the red blood cell. Results Plus: Examiner Comments This response also scores three marks. It explains that there is a higher water potential outside the cell so water enters the cell by osmosis. The cell bursts. Results Plus: Examiner Comments This scores one mark for explaining that water enters the cell by osmosis. (c)(ii) (c)(ii) asks candidates to explain how this difference affects red cells placed in a concentrated salt solution. This item also scored well with many candidates gaining two marks for explaining that water leaves the cell by osmosis from a dilute to a more concentrated solution. This causes the cell to shrink. Some candidates wrote about the cell being plasmolysed which gained no credit. Results Plus: Examiner Comments This gains both marks. It explains that the cell will crenate as water moves out of the cell down a water potential gradient by osmosis. Results Plus: Examiner Comments This also scores two marks for the cell shrinking as water leaving the cell by osmosis. Results Plus: Examiner Comments This scores one mark for the cell shrivels. Results Plus: Examiner Tip The answer can be improved by explaining the direction of osmosis and the gradient causing it. Q14. (a) This question asked candidates to explain how stem cells differ from other types of cell. Most gained one mark for the idea that stem cells are undifferentiated and about half of these went on to state that stem cells can continue to divide and then differentiate into different types of cell. Candidates should be careful to state that stem cells can produce 'different types of cell' rather than simply 'produce more cells'. (b) This question asked candidates to explain how stem cells could enable different blood conditions to be treated. Many candidates found this question challenging and gave vague answers, such as, 'stem cells could produce more blood cells.' Strong answers gave specific details about the blood cell types and conditions, such as 'red blood cells could be made that can increase oxygen transport' or 'more lymphocytes could be made to treat people with immunity issues'. Candidates should always try to give as much specific detail as possible, always focusing on the number of marks allocated. (c) This question asked candidates to explain why using a patient's own stem cells is better than a donor's. Most candidates were able to gain at least one mark, most frequently for stating that the cells would not be rejected as they are genetically identical with the same antigens. Candidates should always be careful to use the terms 'antigen' and 'antibody' accurately. Q15. No Examiner's Report available for this question Q16. No Examiner's Report available for this question Mark Scheme Q1.  (Q01 4SS0/1B, June 2022) Q2.  (Q03 4BI1/2BR, June 2022) Q3.  (Q03 4BI1/2B, June 2022) Q4.  (Q07 4BI1/1B, Nov 2023) Q5.  (Q01 4BI1/1B, Nov 2020) Q6.  (Q06 4BI1/2B, June 2022) Q7. (Q07 4BI1/2B, Nov 2021) Q8. (Q01 4SS0/1B, SAM 0) Q9.  (Q01 4SS0/1B, June 2019) Q10.  (Q02 4BI1/1B, Jan 2020) Q11.  (Q01 4SS0/1B, June 2023) Q12.  Total 8 marks (Q01 4BI1/1B, June 2023) Q13.  Total 12 marks (Q03 4BI1/1B, June 2023) Q14.  (Q06 4BI1/2B, Nov 2023) Q15.  (Q02 4BI1/2B, June 2021) Q16.  (Q01 4SS0/1B, SAM 0) Powered by TCPDF (www.tcpdf.org)