B5 Homeostasis and Response

Transcription

1 B5 Homeostasis and Response Practice questions Name: Class: Date: Time: 209 minutes Marks: 20 marks Comments: HIGHER TIER Page of 68

2 Amylase is an enzyme that digests starch. A student investigated the effect of ph on the activity of amylase. This is the method used.. Mix amylase solution and starch suspension in a boiling tube. 2. Put the boiling tube into a water bath at 25 C. 3. Remove a drop of the mixture every 30 seconds and test it for the presence of starch. 4. Repeat the investigation at different ph values. The table below shows the students results. ph Time when no starch was detected in minutes (a) The student concluded ph 7.25 was the optimum ph for the amylase enzyme. This is not a valid conclusion. Suggest two reasons why.. 2. (2) Page 2 of 68

3 (b) The student did another investigation. This is the method used.. Put amylase solution and starch suspension into a boiling tube. 2. Make the ph Put the boiling tube into a water bath at 25 C. 4. Measure the amount of sugar produced every 30 seconds. The results are shown in the figure below. Calculate the mean rate of sugar produced per minute during the first 5 minutes. Mean rate = units per minute (2) Page 3 of 68

4 (c) Iodine solution is added to a sample taken from the boiling tube after 0 minutes and 60 minutes. Suggest what you would see in these samples. After 0 minutes After 60 minutes (2) (d) The scientist repeated the investigation at 37 C. Draw a line on the figure above to show the results the scientist would get. (2) (e) The same investigation was done at 65 C. How would this affect the results? Explain why. (3) (Total marks) 2 Neurones pass information around the body. (a) Why are reflex reactions important? () Page 4 of 68

5 (b) Caffeine is a drug found in coffee. After a person drinks coffee information passes through neurones in the nervous system more quickly. Suggest a hypothesis for the effect of caffeine concentration on reaction time. () (c) Two students investigated the effect of caffeine concentration on reaction time. This is the method used.. Student A drinks a cup of coffee. 2. Student B holds a ruler above Student A s hand. 3. Student B drops the ruler. 4. Student A catches the ruler as quickly as she can. 5. The distance the ruler falls is recorded. Suggest how this method could be improved to produce valid results. (6) (Total 8 marks) Page 5 of 68

6 3 The nervous system allows humans to respond to their surroundings. The figure below shows two nerve pathways. Nerve pathway A Nerve pathway B (a) Nerve pathway A is 92 cm long. A nerve impulse travels along pathway A at 76.2 m / s. Calculate how long it takes for the nerve impulse to travel the length of the pathway. Use the equation: distance = speed time Time = s (3) (b) Nerve pathways A and B are the same length. The nerve impulse takes longer to travel along pathway A than along pathway B. Use the figure above to explain why. (3) Page 6 of 68

7 (c) Two students compare their reactions using a ruler. This is the method used.. Student A sits with his elbow on a table top. 2. Student B holds the ruler so the bottom of the ruler is level with the top of student A s thumb. 3. Student B drops the ruler. 4. Student A catches the ruler. 5. Record the drop distance. 6. Repeat steps to 5 four more times. 7. Repeat the whole experiment with student A dropping the ruler and student B catching it. Both students are right-handed. Student A uses his right hand to catch the ruler. Student B uses her left hand to catch the ruler. The table below shows the students results. Student Drop distance in mm Test Test 2 Test 3 Test 4 Test 5 Student A right hand Student B left hand What is the range of student A s results? () Page 7 of 68

8 (d) The students are testing the hypothesis: The drop distance of the ruler is smaller when a right-handed person uses their right hand to catch the ruler. The students results in the table above are not a good test of the hypothesis. Suggest what the students should have done to test the hypothesis. (3) Page 8 of 68

9 (e) Student A s mean reaction time was 0.9 s. Mean reaction time can be calculated using the equation: Calculate the mean reaction time for Student B. Give your answer to two significant figures. Student B s results are repeated here to help you answer the question. Drop distance in mm Test Test 2 Test 3 Test 4 Test 5 Student B left hand Mean reaction time = s (4) (Total 4 marks) Page 9 of 68

10 4 The rate of chemical reactions can be changed by changing the conditions. (a) Methane burns in oxygen to produce carbon dioxide and water. The activation energy for the reaction is 2648 kj / mol. The reaction gives out 88 kj / mol of energy. The figure below shows the reaction profile for this reaction. Complete the reaction profile. Draw arrows to represent: the activation energy the energy given out. (4) (b) What percentage of the activation energy is the energy given out? () (c) Calcium carbonate decomposes when it is heated: The decomposition of calcium carbonate is an endothermic reaction. How would the reaction profile for decomposition of calcium carbonate be different from the reaction profile of methane burning in oxygen? () Page 0 of 68

11 (d) Catalysts are used in chemical reactions in industry. Give two properties of catalysts. For each property, explain why it makes the catalyst useful in industry. (4) (e) Enzymes are biological catalysts. What type of molecule is an enzyme? Tick one box. Carbohydrate Hydrocarbon Lipid Protein () (f) If enzymes are denatured they stop working. Give two ways an enzyme can be denatured.. 2. (2) Page of 68

12 (g) An enzyme called lactase catalyses the reaction that breaks down lactose to smaller molecules. One model used to explain how enzymes affect reactions is called the lock and key model. Use the lock and key model to explain why lactase cannot be used to speed up all chemical reactions. (3) (Total 6 marks) 5 Amylase catalyses the breakdown of starch into sugars. A student investigated the effect of amylase on the reaction at different temperatures. Figure shows the apparatus the student used. Figure Page 2 of 68

13 This is the method used.. Put starch suspension into a test tube. 2. Add amylase solution. 3. Put the test tube in a beaker of water at 5 C. 4. Remove a small sample of the mixture every 30 seconds and put in a spotting tile. 5. Test the sample for starch. 6. Time how long it takes to break down all of the starch in the mixture. 7. Repeat steps 5 at 20 C, 25 C and 30 C. 8. Repeat for each temperature twice more. The table below shows the student s results. Time taken until there was no starch in the sample in minutes Temperature in C Test Test 2 Test 3 Mean (a) One of the results in the table above is anomalous. Draw a ring around the anomalous result. () (b) Calculate the mean for 30 C. () Page 3 of 68

14 (c) Figure 2 shows a graph of the student s results. Figure 2 Use the graph to predict how long it would take to break down all of the starch at 0 C. Time = minutes () (d) The student tested samples of the mixture for starch every 30 seconds. In each test she added one drop of iodine to the sample in the spotting tile. Predict the colour of the samples from the 20 C test at 4.0 minutes and 7.0 minutes. Colour at 4.0 minutes Colour at 7.0 minutes (2) Page 4 of 68

15 (e) The student did a fourth test at 30 C. In this test the starch did not break down, even after 45 minutes. Why did the amylase not break down the starch in this test? Tick one box. The amylase solution and the starch suspension were mixed before the start of the experiment. The amylase solution had been prepared with water at 95 C. The amylase solution had been prepared with water at 20 C. The amylase solution had been stored in the fridge. () (f) The student made the following conclusion about the optimum temperature for amylase to work at. Amylase works fastest at 40 C Her teacher said that this is not a valid conclusion from her results. Describe how the student could change her method to give results that would improve the validity of her conclusion. (6) (Total 2 marks) Page 5 of 68

16 6 The human body is organised to carry out many different functions. (a) Use words from the box to complete Figure by putting the parts of the body in order of size from smallest to largest. The smallest one has been done for you. (2) (b) The stomach is made of different types of tissue. Draw one line from each type of stomach tissue to the correct description. (3) Page 6 of 68

17 (c) Animals can react to their surroundings because they have nervous systems. A student investigated the behaviour of small animals called woodlice. The student set up the investigation as shown in Figure 2. The student covered one half of a Petri dish with black paper to make that side of the Petri dish dark. The other side had no cover. The student put five woodlice into each side of the dish and then put the clear Petri dish lid back on the dish. Figure 2 After 30 minutes, all the woodlice had moved to the dark side of the Petri dish. Page 7 of 68

18 (i) In this investigation, what is the stimulus that the woodlice responded to? () (ii) In this investigation, what is the response that the woodlice made? () (iii) The student concluded that woodlice prefer dark conditions. Give two ways in which the student could improve the investigation to be sure that his conclusion was correct.. 2. (2) (Total 9 marks) 7 This question is about hormones. (a) (i) Hormones carry messages. What type of messenger is a hormone? Draw a ring around the correct answer. chemical electrical environmental () (ii) Which part of the brain secretes hormones? Draw a ring around the correct answer. cerebellum medulla pituitary gland () Page 8 of 68

19 (b) Figure shows the level of a pregnancy hormone over a 40-week pregnancy. This hormone can be detected in a pregnancy test. Figure A woman takes a pregnancy test. In which week of pregnancy is the test most likely to give a positive result? Use information from Figure. Write the correct answer in the box. () Page 9 of 68

20 (c) Figure 2 shows the levels of three other hormones during pregnancy. The baby is usually born at about 40 weeks. Figure 2 Adaptation by kind permission of Biozone International (i) Describe the patterns in the levels of oestrogen and progesterone from 0 to 36 weeks. (4) (ii) Which hormone is likely to stimulate contractions of the uterus (womb) when the baby is born? Use information from Figure 2 to give a reason for your answer. (2) (Total 9 marks) Page 20 of 68

21 8 (a) Control systems help to keep conditions in the human body relatively constant. What is the general name for the processes that keep body conditions relatively constant? Draw a ring around the correct answer. eutrophication homeostasis hydrotropism () (b) The concentration of glucose in the blood is controlled by hormones. Use the correct answer from the box to complete each sentence. glucagon glycerol glycogen kidney liver pancreas When the blood glucose concentration increases, an organ called the releases the hormone insulin. Insulin causes glucose to move from the blood into the cells of the muscles and the. Inside these organs, the glucose is changed into a carbohydrate called, which can be stored. When the blood glucose concentration falls, another hormone is released, which causes the storage carbohydrate to break down into glucose again. This hormone is called. (4) Page 2 of 68

22 (c) A person with Type diabetes does not make enough insulin. The person needs to test their blood at intervals throughout the day. If the concentration of glucose in their blood is too high, the diabetic person needs to inject insulin. (i) Insulin is a protein. It must be injected and cannot be taken by mouth. Explain why. (2) (ii) Apart from injecting insulin, give one other way that a diabetic person could help to control the concentration of glucose in their blood. () Page 22 of 68

23 (d) Pet dogs have been trained to detect if the concentration of glucose in the blood of their diabetic owners is outside the normal healthy range. These dogs are called medical response dogs. The dogs respond in different ways. They may bark, jump up, or stare at their owners.they may even fetch a blood-testing kit. (i) Suggest what stimulus the dogs might be responding to when they behave like this. () (ii) Table shows how the concentration of glucose varied in blood samples from five diabetic people. Measurements were made both before and after getting a medical response dog. Table Mean percentage of blood samples with different concentrations of glucose from the five diabetic people Number of blood samples measured Low glucose Within normal range of glucose High glucose Before getting a dog After getting a dog A survey was made of the effect of a medical response dog on the lives of 6 diabetic people. Table 2 shows how well these diabetic people agreed with each statement in the survey. Table 2 Statement in survey Totally agree Somewhat agree Neither agree Somewhat nor disagree disagree Totally disagree I am more independent since getting my dog. There are disadvantages to having a medical Page 23 of 68

24 response dog. I trust my dog to alert me when my sugar levels are low. I trust my dog to alert me when my sugar levels are high Evaluate how useful medical response dogs are for warning diabetic people that the concentration of glucose in their blood is outside the normal range. Use information from Tables and 2. (5) Page 24 of 68

25 (e) Table 3 shows the concentrations of some substances in the urine of a non-diabetic person and in the urine of a diabetic person. Table 3 Concentration of substance in urine in g per dm 3 Substance Non-diabetic person Diabetic person Protein 0 0 Glucose Urea Sodium ions Compare the results for the non-diabetic person and the diabetic person. Give reasons for any differences. Use your knowledge of how the kidney works. (5) (Total 9 marks) Page 25 of 68

26 9 This question is about the nervous system. (a) Describe the function of receptors in the skin. (2) (b) A response is caused when information in the nervous system reaches an effector. (i) There are two different types of effector. Complete the table to show: the two different types of effector the response each type of effector makes. (4) (ii) Some effectors help to control body temperature. Give one reason why it is important to control body temperature. () (Total 7 marks) Page 26 of 68

27 0 The diagram shows the position of two glands, A and B, in a woman. (a) (i) Name glands A and B. A B (2) (ii) Gland A produces the hormone Follicle Stimulating Hormone (FSH). FSH controls changes in gland B. How does FSH move from gland A to gland B? () Page 27 of 68

28 (b) (i) A woman is not able to become pregnant. The woman does not produce mature eggs. The woman decides to have In Vitro Fertilisation (IVF) treatment. Which two hormones will help the woman produce and release mature eggs? Tick ( ) one box. FSH and Luteinising Hormone (LH) FSH and oestrogen Luteinising Hormone (LH) and oestrogen () (ii) Giving these hormones to the woman helps her to produce several mature eggs. Doctors collect the mature eggs from the woman in an operation. Describe how the mature eggs are used in IVF treatment so that the woman may become pregnant. (3) (iii) IVF clinics have been set a target to reduce multiple births. At least 76% of IVF treatments should result in single babies and a maximum of 24% of treatments should result in multiple births. Suggest one reason why the clinics have been set this target to reduce multiple births. () Page 28 of 68

29 (c) Two clinics, R and S, used IVF treatment on women in Doctors at each clinic used the results of the treatments to predict the success rate of treatments in The table shows the information. Total number of IVF treatments in 2007 Number of IVF treatments resulting in pregnancy in 2007 Predicted percentage success rate in 2008 Clinic R Clinic S (i) Compare the success rates of the two clinics in () (ii) The range of the predicted success rate in 2008 for clinic R is much smaller than the range of the predicted success rate for clinic S. Suggest why. (2) (Total marks) Page 29 of 68

30 People with Type diabetes cannot control the concentration of glucose in their blood. This is because they do not produce the hormone insulin. The same concentration and volume of glucose solution is given to two people. Person with Type diabetes. Person without Type diabetes. Figure shows how the blood glucose concentration of these people changes after they each drink a glucose solution. Figure Page 30 of 68

31 (a) The blood glucose concentration increases at a faster rate in the person with diabetes compared to the person without diabetes. Calculate how much faster the rate of increase in blood glucose concentration is in the person with diabetes. Give the rate of increase for the first 30 minutes after drinking the glucose solution. Give your answer in units / h. Units / h (2) (b) The blood glucose concentration of the person without diabetes starts to change 30 minutes after drinking the glucose solution. Explain why the blood glucose concentration changes. (2) Page 3 of 68

32 (c) People with diabetes should try to keep their blood glucose concentration within the same range as a person without diabetes. Most people with Type diabetes regularly check their blood glucose concentration using a meter, as shown in Figure 2. The meter reading is used to estimate how much insulin they need to inject. Figure 2 Vincente Barcel/Hemera/Thinkstock Figure 3 shows a new system. It is connected to the person all the time. Figure 3 The new system: gives better control of blood glucose concentration reduces the number of times the glucose concentration falls too low. Page 32 of 68

33 Evaluate the two systems as methods for controlling blood glucose concentrations for people with Type diabetes. Give a justified conclusion to your evaluation. (4) (d) How does the body respond if slightly too much insulin is injected into the body. (5) (Total 3 marks) Page 33 of 68

34 2 Hormones are released from glands. (a) Which gland produces hormones to control other glands in the endocrine system? Tick one box. Adrenal Ovary Pituitary Thyroid () Page 34 of 68

35 (b) The figure below shows the level of adrenaline in a man s bloodstream while he was watching a 2-minute film. Calculate the percentage increase in adrenaline after point B. Percentage increase in adrenaline = (2) (c) Suggest why the percentage increase in adrenaline after point B is different from the percentage increase after point A. (2) Page 35 of 68

36 (d) Adrenaline causes changes in the body to prepare for a fight or flight response. What changes in the man s body are caused by adrenaline? (2) (Total 7 marks) 3 The figure below shows how the concentrations of the reproductive hormones in the blood of a woman change over 28 days. (a) Name hormones A and B. A B (2) (b) Use information from the figure above to explain what happens on Day 4. (2) Page 36 of 68

37 (c) In Vitro Fertilisation (IVF) treatment can be used to help women become pregnant. IVF uses some of the hormones shown in the figure above. Explain why IVF increases the chance of some women becoming pregnant. (6) (Total 0 marks) 4 In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. Homeostasis keeps conditions in the body relatively constant. The amount of water in the body is controlled by homeostasis. Kidney function is controlled by a gland in the brain. Page 37 of 68

38 Describe how the water content of the blood is controlled. (Total 6 marks) Page 38 of 68

39 5 The diagram below shows how a nerve impulse passing along a relay neurone causes an impulse to be sent along another type of neurone, neurone X. (a) What type of neurone is neurone X? () (b) Describe how information passes from the relay neurone to neurone X. Use the diagram to help you. (3) (c) Scientists investigated the effect of two toxins on the way in which information passes across synapses. The table below shows the results. Toxin Curare Strychnine Effect at the synapse Decreases the effect of the chemical on neurone X Increases the amount of the chemical made in the relay neurone Page 39 of 68

40 Describe the effect of each of the toxins on the response by muscles. Curare Strychnine (2) (Total 6 marks) 6 Phenylketonuria (PKU) is an inherited condition. PKU makes people ill. (a) PKU is caused by a recessive allele. (i) What is an allele? () (ii) What is meant by recessive? () (b) The diagram below shows the inheritance of PKU in one family. (i) Give one piece of evidence from the diagram that PKU is caused by a recessive allele. () Page 40 of 68

41 (ii) Persons 6 and 7 are planning to have another child. Use a genetic diagram to find the probability that the new child will have PKU. Use the following symbols in your answer: N = the dominant allele for not having PKU n = the recessive allele for PKU. Probability = (4) (c) Persons 6 and 7 wish to avoid having another child with PKU. A genetic counsellor advises that they could produce several embryos by IVF treatment. (i) During IVF treatment, each fertilised egg cell forms an embryo by cell division. Name this type of cell division. () (ii) An embryo screening technique could be used to find the genotype of each embryo. An unaffected embryo could then be placed in person 7 s uterus. The screening technique is carried out on a cell from an embryo after just three cell divisions of the fertilised egg. How many cells will there be in an embryo after the fertilised egg has divided three times? () (iii) During embryo screening, a technician tests the genetic material of the embryo to find out which alleles are present. The genetic material is made up of large molecules of a chemical substance. Name this chemical substance. () (d) Some people have ethical objections to embryo screening. (i) Give one ethical objection to embryo screening. () Page 4 of 68

42 (ii) Give one reason in favour of embryo screening. () (Total 2 marks) 7 The diagram shows the structures involved in the knee-jerk reflex. When the person is hit at point P, the lower leg is suddenly raised. (a) Name the structures labelled A, B and C. A B C (3) (b) How is information passed across a synapse? () (c) What is the effector in this response? () (Total 5 marks) Page 42 of 68

43 8 The number of cases of Type 2 diabetes in the UK is increasing rapidly. (a) Describe how insulin and glucagon help control the blood sugar concentration in a healthy person. (6) (b) What is Type 2 diabetes? () Page 43 of 68

44 (c) Body mass index (BMI) is a person s body weight divided by the square of his or her height. (i) Graph shows the relationship between BMI and the percentage probability of developing Type 2 diabetes. Graph Percentage probability of developing Type 2 diabetes Suggest an explanation for the relationship between BMI and the risk of developing Type 2 diabetes. (2) Page 44 of 68

45 (ii) Graph 2 shows changes in the number of new cases of Type 2 diabetes in the UK. Graph 2 Year Suggest explanations for the trend shown by the data in Graph 2. (3) (Total 2 marks) Page 45 of 68

46 9 The pancreas and the liver are both involved in the control of the concentration of glucose in the blood. The liver has two veins: the hepatic portal vein taking blood from the small intestine to the liver the hepatic vein taking blood from the liver back towards the heart. Scientists measured the concentration of glucose in samples of blood taken from the hepatic portal vein and the hepatic vein. The samples were taken hour and 6 hours after a meal. Graph shows the concentration of glucose in the two blood vessels hour after the meal. Graph Blood vessel (a) The concentration of glucose in the blood of the two vessels is different. Explain why. (3) Page 46 of 68

47 (b) Graph 2 shows the concentration of glucose in the two blood vessels 6 hours after the meal. Graph 2 Blood vessel (i) The concentration of glucose in the blood in the hepatic portal vein hour after the meal is different from the concentration after 6 hours. Why? () Page 47 of 68

48 (ii) The person does not eat any more food during the next 6 hours after the meal. However, 6 hours after the meal, the concentration of glucose in the blood in the hepatic vein is higher than the concentration of glucose in the blood in the hepatic portal vein. Explain why. (3) (Total 7 marks) Page 48 of 68

49 20 The diagram shows the nervous pathway used to coordinate the knee-jerk reflex. When the person is hit at point P, the lower leg is suddenly raised. (a) Name neurones A, B and C. A B C (3) (b) The receptor in the muscle in the leg is sensitive to a stimulus. Suggest the stimulus. () Page 49 of 68

50 (c) Describe what happens at the synapse during this reflex. (3) (Total 7 marks) Page 50 of 68

51 Mark schemes (a) any two from: same result at ph 7 and 7.5 or could be any ph between 7 and 7.5 or not tested at ph 7.25 or need to test at smaller ph intervals (between 7 and 7.5) accuracy of result only to nearest 0.5 minutes no repeats difficult to determine end point (colour) 2 (b) 2.7 / (units per minute) allow 0.52 with no working shown for 2 marks allow mark for 0.52 or 0.56 (c) (d) (e) (after 0 minutes) solution goes black (after 60 minutes) solution stays the same or does not go black or goes slightly orange steeper curve levels off at.8 units and before 45 minutes no / little sugar produced allow a correct description of what the graph would look like (because at 65 C) the enzyme will be denatured allow (because) the enzyme s shape will be changed or (because) the active site is damaged Page 5 of 68

52 (so) will no longer fit the starch or (so) will not be able to catalyse the reaction [] 2 (a) fast reaction to reduce / protect from harm allow named examples (b) higher caffeine concentration causes shorter reaction time. allow converse ignore faster / slower reaction time (c) Level 3 (5 6 marks): A coherent method is described with relevant detail, which demonstrates a broad understanding of the relevant scientific techniques and procedures. The steps in the method are logically ordered. The method would lead to the collection of valid results. Level 2 (3 4 marks): The bulk of a method is described with mostly relevant detail, which demonstrates a reasonable understanding of the relevant techniques and procedures. The method may not be in a completely logical sequence and may be missing some detail. Level ( 2 marks): Discrete relevant points are made which demonstrate some understanding of the relevant scientific techniques and procedures. They may lack a logical structure and would not lead to the production of valid results. 0 marks: No relevant content. Indicative content use decaffeinated coffee as control control volume of coffee blind trial or do not tell students which coffee they are drinking left for standard time between drink and test at least 0 minutes control start position of ruler control other factors such as light in the room same person for different concentrations repeat for each caffeine concentration use a range of caffeine concentrations start with lowest concentration of caffeine use caffeine solution instead of coffee to control for other ingredients repeat investigation with more people and calculate means 6 [8] 3 (a) 0.92 = 76.2 time Page 52 of 68

53 time = = 0.02 allow 0.02 with no working shown for 3 marks (b) (c) (d) pathway B has two synapses allow converse for pathway A chemicals diffuse across each synapse which slows down the impulse use the same person for each test use left hand and right hand use a bigger sample size or more people allow take more readings with each person (e) mean drop distance = ( ) 5 = mm = m mean reaction time = = 0.22 incorrect sig. figs max. 3 marks allow 0.22 with no working shown for 4 marks [4] 4 (a) products below reactants correct energy profile activation energy correctly labelled energy given out correctly labelled Page 53 of 68

54 (b) 3 (%) (c) (d) (e) (f) (g) the products would be above the reactants catalysts increase rate of reaction mark for each property mark for each explanation so products formed in less time or catalysts lower activation energy explanation must be linked correctly to the property to gain the mark so lowers energy requirements or catalysts not used up in the reaction so only an initial outlay needed or only a small amount of catalyst needed so small initial cost Protein high temperatures extremes of ph lactase acts as the lock, lactose is the key (substrate) lactase has an active site which will only fit lactose molecules max. 4 so lactase will not work with other molecules [6] 5 (a) 6. circled on table (5 C, test ) Page 54 of 68

55 (b).8 do not allow.83 (c) (d) 6 (minutes) correct number extrapolated from curve 4.0 min blue / black / purple 7.0 min yellow / orange / brown (e) The amylase solution had been prepared with water at 95 C (f) Level 3 (5 6 marks): A clear and coherent method is described using logical steps and demonstrating a good understanding of how to improve the validity of the method. The method would lead to the production of valid results that would give rise to a more valid conclusion. Level 2 (3 4 marks): The substantive content of a method is present and demonstrates reasonable understanding of how to improve the validity but may be missing some detail. The plan may not be in a completely logical sequence but leads towards the measurement of rate of the reaction. Level ( 2 marks): Simple relevant statements made, which demonstrate limited understanding of how to improve the experimental method. The response lacks logical structure and would not lead to the production of valid results or a more precise optimum temperature. 0 marks: No relevant content Indicative content conduct at a greater range of temperatures use temperatures both above and below 40 C use smaller temperature intervals to get a more accurate optimum (eg go up in 2 C increments) take samples at smaller time intervals to get a more accurate result for time taken control the volume of starch used (eg 5 cm 3 ) control the volume of the amylase solution (eg cm 3 ) control the temperature (eg using a water bath) heat the two solutions separately before mixing control the concentration of the starch solution control the concentration of the amylase solution 6 [3] Page 55 of 68

56 6 (a) (b) tissue organ organ system one right for mark three right for 2 marks Epithelial tissue covers the outside and the inside of the stomach more than one line from a tissue = no mark Glandular tissue produces digestive juices Muscular tissue allows food to be churned around the stomach 2 (c) (i) light ignore dark (ii) (iii) moving (to the dark) any two from: use more woodlice repeat the experiment run for a longer time 2 [9] 7 (a) (i) chemical (ii) (b) 8 pituitary gland allow 9 or 0 Page 56 of 68

57 (c) (i) any four from: progesterone starts being produced at 4 weeks / no progesterone before 4 weeks and then / from 4 weeks increases oestrogen at constant / low level (from 0) to 20 weeks and then / from 20 weeks increases from weeks level of O rises more steeply than that of P or P is always higher than 0 from 6 to 36 weeks if no other marks awarded, allow progesterone and oestrogen both increase / rise for mark. 4 (ii) oxytocin level of oxytocin increases just before birth [9] 8 (a) homeostasis (b) in sequence: pancreas liver glycogen glucagon correct spelling only correct spelling only (c) (i) broken down / digested further detail eg into amino acids / by enzymes / by proteases (ii) diet / eating less sugar / less fat ignore balanced diet or ignore dieting / slimming diet exercise accept pancreas transplant Page 57 of 68

58 (d) (i) sensible suggestion eg (owner s) smell / sweating / change in owner s behaviour / dizziness / tiredness (ii) any five from: allow mark for justified conclusion do not allow full marks unless at least pro and con. Pro: % below normal decreases % in normal increases reliable / repeatable / valid data as large number of samples do not allow accurate / precise patients express satisfaction. (e) Con: may not be reliable as blood glucose measurements for only 5 patients / survey of only 6 (dog owners) % above normal increases / dogs are less good at detecting high glucose. glucose in urine of diabetic (and not in the non-diabetic) urea and Na+ ions are similar in each / slightly lower in diabetic 5 + any three from: no protein in either urine sample because protein too large / does not pass through filter glucose passes through filter in kidney ignore glucose is reabsorbed non-diabetic: the / all glucose is reabsorbed / taken back into blood diabetic: (too much glucose so) cannot all be reabsorbed because diabetic has high concentration of glucose in blood urea and Na+ lower in diabetic because less water is reabsorbed (due to extra glucose in filtrate). 3 [9] 9 (a) detect changes in surroundings or detect stimuli allow any named stimulus for skin convert information to impulse allow send impulse to sensory neurones / brain Page 58 of 68

59 (b) (i) muscle contract(ion) gland release / secrete / produce chemical / hormone / enzyme mark for each effector mark for each response response must match type of effector (if given) ignore examples ignore relax(ation) / movement for contraction do not allow expansion for muscles 4 (ii) any one from: (maintain temperature at which) enzymes work best so chemical reactions are fast(est) prevent damage to cells / enzymes allow prevent enzymes being denatured (by temperature being too high) [7] 0 (a) (i) A pituitary allow hypothalamus B ovary / ovaries (ii) in blood (stream) accept in plasma ignore dissolved (b) (i) FSH and Luteinising Hormone (LH) (ii) fertilised OR reference to sperm form embryos / ball of cells or cell division (embryo) inserted into mother s womb / uterus allow (fertilised egg) is inserted into mother s womb / uterus Page 59 of 68

60 (iii) any one from: multiple births lead to low birth weight multiple births cause possible harm to mother / fetus / embryo / baby / miscarriages allow premature ignore reference to cost / ethics / population (c) (i) any one from: almost identical allow S (slightly) more successful both approximately 20% (ii) larger numbers (in clinic R) (in 2007) allow only 98 (in S) (compared to 004 (in R)) results likely to be more repeatable (in 2008) allow more reliable do not accept more reproducible / accurate / precise [] (a) (76 28) 2 96 (units / h) allow 96 (units / h) with no working shown for 2 marks allow.6 units / min for mark allow answer in range of (units / h) for mark (b) increased blood glucose concentration causes insulin release from pancreas which stimulates cells to absorb glucose / sugar from the blood, so blood glucose concentration decreases Page 60 of 68

61 (c) any three from: at least one advantage and one disadvantage of the system(s) must be given for full marks allow responses phrased in terms of the meter and injection systems advantages of the new system: better control so reduces risk of future health problems allow fewer low / high blood glucose periods so safer no need to estimate dose of insulin less chance of giving too much / little insulin system works automatically / continuously so no need to test / inject disadvantages of the new system: (d) system is always attached so may restrict activities allow pump is difficult to hide pump has to be carried somewhere allow risk of discomfort pump will need re-filling risk of infection or risk of tissue damage (at injection site) line might come out accept new system more expensive qualified conclusion: a statement as to which system is better with reference to at least one advantage and one disadvantage for example, the new system is better because although it is more expensive, it works automatically blood glucose concentration goes too low blood glucose concentration detected by pancreas pancreas releases glucagon (glucagon causes) cells to convert to glycogen into glucose 3 glucose released into blood [3] 2 (a) Pituitary Page 6 of 68

62 (b) (c) (d) = 50 (%) the level in the blood is already higher than it was before point A levels hadn t returned to normal yet (before the next scare) allow he had already been scared so he was expecting the second scare increased oxygen to brain / muscles increased glucose to brain / muscles [7] 3 (a) A FSH allow follicle stimulating hormone B Progesterone (b) LH peaks allow luteinising hormone which causes an egg to be released. Page 62 of 68

63 (c) Level 3 (5 6 marks): A detailed and coherent explanation is given, which logically links the role of different hormones to their use in IVF and a clear explanation of how IVF increases the chance of a successful pregnancy. Level 2 (3 4 marks): An attempt is made to link the role of hormones to their use in IVF. The logic used in explaining how IVF increases the chance of a successful pregnancy may not be clear or linked to the hormones. Level ( 2 marks): Discrete relevant points made. The logic may be unclear and links may not be made. 0 marks: No relevant content Indicative content Identification of hormones used in IVF: FSH LH. Role of hormones in IVF: FSH causes eggs to mature LH causes the eggs to be released. Effect on chance of successful pregnancy: high levels of hormones cause many eggs to be matured and released sperm and eggs are collected and eggs are fertilised (so increased probability of fertilisation) fertilised eggs are given time to develop into a small ball of cells some are transferred into the mother (uterus), to increase the probability of one successfully implanting. 6 [0] Page 63 of 68

64 4 Marks awarded for this answer will be determined by the Quality of Communication (QC) as well as the standard of the scientific response. Examiners should also refer to the information on page 5, and apply a best-fit approach to the marking. 0 marks No relevant content. Level ( 2 marks) There is a brief description of kidney function including a mention of pituitary gland or hormones but roles may be confused. Level 2 (3 4 marks) There is a clear description of kidney function in relation to fluctuations in blood water levels and the roles of the pituitary gland or hormone is mentioned with correct role. Level 3 (5 6 marks) There is a clear and detailed scientific description of kidney function in relation to fluctuations in blood water levels and of the roles of the pituitary gland and ADH. examples of biology points made in the response: if water content too low, ADH released from pituitary gland into the blood (causing) kidney reabsorbs more water more concentrated / small volume urine produced if water content too high, ADH lowered / not produced less water reabsorbed by kidney more dilute / larger volume urine produced full marks may be awarded for detailed description of either water loss or gain [6] 5 (a) motor allow efferent / postsynaptic allow another relay (neurone) (b) release of chemical (from relay neurone) allow ecf for motor neurone from (a) allow release of neurotransmitter / named example chemical crosses gap / junction / synapse allow diffuses across allow chemical moves to X chemical attaches to X / motor / next neurone (causing impulse) Page 64 of 68

65 (c) (curare) decrease / no contraction accept (muscle) relaxes (strychnine) increase / more contraction if no other mark awarded allow mark for (curare) decrease / no response and (strychnine) increase / more response [6] 6 (a) (i) one form of a / one gene do not allow a type of gene allow a mutation of a gene (ii) not expressed if dominant / other allele is present / if heterozygous or only expressed if dominant allele not present / or no other allele present allow need two copies to be expressed / not expressed if only one copy / only expressed if homozygous (b) (i) two parents without PKU produce a child with PKU / 6 and 7 0 allow it skips a generation (ii) genetic diagram including: accept alternative symbols if defined Parental gametes: 6: N and n and 7: N and n derivation of offspring genotypes: NN Nn Nn nn allow genotypes correctly derived from student s parental gametes identification: NN and Nn as non-pku OR nn as PKU allow correct identification of student s offspring genotypes correct probability only: 0.25 / ¼ / in 4 / 25% / : 3 do not allow 3 : / : 4 do not allow if extra incorrect probabilities given Page 65 of 68

66 (c) (i) mitosis (ii) 8 correct spelling only (iii) DNA allow deoxyribonucleic acid do not allow RNA / ribonucleic acid (d) (i) may lead to damage to embryo / may destroy embryos / embryo cannot give consent allow avoid abortion allow emotive terms eg murder religious argument must be qualified allow ref to miscarriage allow idea of avoiding prejudice against disabled people allow idea of not producing designer babies (ii) any one from: prevent having child with the disorder / prevent future suffering / reduce incidence of the disease ignore ref to having a healthy child ignore ref to selection of gender embryo cells could be used in stem cell treatment allow ref to long term cost of treating a child (with a disorder) allow ref to time for parents to become prepared [2] 7 (a) A sensory (neurone) ignore nerve B motor (neurone) ignore nerve C spinal cord / central nervous system / white matter accept grey matter (b) by chemical / substance allow transmitter Page 66 of 68

67 (c) muscle allow extensor ignore muscle names [5] 8 (a) any six from: hormone(s) / named produced by pancreas if blood glucose levels are too high, insulin is produced / released allowing glucose to move from the blood into the cells / named eg liver glucose is converted to glycogen if blood glucose levels fall, glucagon is produced / released glycogen is converted to glucose causing glucose to be released into the blood 6 (b) diabetes that occurs when the body (cells) do not respond / are less responsive to insulin (c) (i) higher BMIs due to increase in mass / weight (relative to height) / obesity obesity / being overweight / being fat is a (significant) risk factor for Type 2 diabetes allow causes Type 2 diabetes (ii) any three from: related to described change in diet eg fast foods and less exercise which increases the chance of obesity / increases BMI increased awareness has helped to slow the increase 3 [2] 9 (a) (concentration high) in the hepatic portal vein is blood with glucose absorbed from the intestine concentration is lower in the hepatic vein because insulin (has caused) glucose to be converted into glycogen or allows glucose into liver cells (b) (i) (after 6 hours) most of the glucose has been absorbed from the intestine or from food into the blood Page 67 of 68

68 (ii) because glucagon (made in the pancreas) causes if biological terms incorrectly spelt they must be phonetically accurate do not accept glucagon made / produced by the liver glycogen to be converted into glucose glucose released into blood allow the liver maintains the correct / constant level of glucose in the blood [7] 20 (a) (b) A sensory B motor C relay stretch ignore nerve / neuron(e) throughout accept afferent accept efferent accept intermediate allow pressure / pull / tension (in muscle) allow a hit at (point) P ignore pain (c) any three from: chemical (release) accept neurotransmitter / acetylcholine diffuses (across the gap / synapse) transmits impulse / information (across synapse) allow transmits signal / message between neurones / nerve cells / named if named, must be either sensory / A to relay / C or relay / C to motor / B allow to the next neurone 3 [7] Page 68 of 68