Oxford ambridge and RSA Tuesday 23 May 2017 Morning AS GE APPLIED SIENE G623/02 ells and Molecules *5196836492* andidates answer on the Question Paper. OR supplied materials: None Other materials required: Electronic calculator Ruler (cm/mm) Duration: 45 minutes * G 6 2 3 0 2 * INSTRUTIONS TO ANDIDATES Write your name, centre number and candidate number in the boxes above. Please write clearly and in capital letters. Use black ink. B pencil may be used for graphs and diagrams only. Answer all the questions. Read each question carefully. Make sure you know what you have to do before starting your answer. Write your answer to each question in the space provided. If additional space is required, you should use the lined page(s) at the end of this booklet. The question number(s) must be clearly shown. Do not write in the barcodes. For Examiner s Use INFORMATION FOR ANDIDATES 1 The number of marks is given in brackets [ ] at the end of each question or part question. 2 The total number of marks for this paper is 45. Where you see this icon you will be awarded marks for the 3 quality of written communication in your answer. This means, for example, you should: 4 ensure that text is legible and that spelling, punctuation and 5 grammar are accurate so that meaning is clear; organise information clearly and coherently, using specialist 6 vocabulary when appropriate. You may use an electronic calculator. You are advised to show all the steps in any calculations. Total This document consists of 16 pages. Any blank pages are indicated. [D/102/6776] D (KN/F) 136658/2 OR is an exempt harity Turn over
2 Answer all the questions. 1 Students were given two food samples to test. The results of these tests are shown in Table 1. Food Sample olour after testing with reagent Iodine solution Biuret Benedict s A Yellow Lilac Blue B Blue/Black Pale blue Brick red Table 1 (a) Use Table 1 to state the substance(s) which were present in: Food sample A... Food sample B... [2] (b) (i) State the chemical reagent(s) that could be used to show the presence of a lipid.... [1] (ii) Describe the result of the test if a lipid was present....... [1]
3 Turn over (c) Fig. 1 represents the structure of a typical triglyceride, a type of lipid. O O O O O O X Y Z Fig. 1 A typical triglyceride consists of three fatty acid chains and one other organic molecule. (i) What organic molecule combines with the fatty acid chains to form a triglyceride?... [1] (ii) In Fig. 1, which fatty acid chain(s) marked X, Y and Z, is/are unsaturated? Give a reason for your answer. Unsaturated fatty acid(s)... Reason... [2] (d) Describe how the structure of the molecule shown in Fig. 1 would differ if it was present in the cell membrane of a white blood cell.... [1] [Total: 8]
2 Lipases are enzymes which break down triglycerides (lipids) in natural oils and fats. 4 Lipases are one of the most common types of enzymes used in industry to make detergents, perfumes, cosmetics and biodiesel. (a) State the type of reaction and the type of chemical bond broken, when triglycerides are broken down by lipases. Type of reaction... Type of bond... [2] (b) It is possible to attach enzymes such as lipases to beads of calcium alginate. Enzymes that have been fixed in this way are called immobilised enzymes. If these beads are then placed in a column, the lipase enzymes are able to break down triglycerides without contaminating the product with the enzyme. Fig. 2.1 shows the apparatus that a group of students used to investigate lipase activity. triglyceride lipase immobilised in calcium alginate column containing alginate beads filter products Fig. 2.1 (i) Suggest a suitable test which the students could use to show that triglycerides had been broken down into products by lipase....... [1]
(ii) 5 Why did the students choose this test?...... [1] (c) The students then investigated the effect of a range of triglyceride concentrations on the rate of lipase activity. The concentration of lipase remained the same. Fig. 2.2 shows the changes in the rate of the reaction. rate of reaction B D A 0 5 10 15 20 25 30 triglyceride concentration / arbitrary units Fig. 2.2 Suggest and explain what limits the rate of the reaction between points A and B.... [2] Turn over
6 (d) Describe and explain the effect of excess triglyceride concentration on the rate of the reaction between points and D.... [2] (e) Suggest two factors, other than lipase concentration, which the students would need to control during this investigation. 1... 2... [2] [Total: 10]
3 Fig. 3.1 is a diagram of part of an electron micrograph of a cell. 7 P Q 4 µ m R Fig. 3.1 (a) Name the structures P, Q and R. P... Q... R... [3] (b) What is the magnification of the electron micrograph shown in Fig. 3.1? 1mm = 1000 μm Show your working. magnification =... [2] Turn over
8 (c) A teacher produced a set of flash cards on microscopy and cell structure. Imagine you are one of her students using these cards. Each card has a description on one side and the name of the organelle on the other side. Fig. 3.2 shows an example flash card. Description This cell organelle digests worn out organelles and breaks down dead cells. Organelle Lysosome Fig. 3.2 For each description below, (i) to (iii), write the name of the organelle in the right hand box. Description (i) Organelle (i) The site of translation of mrna and assembly of peptide chains. Description (ii) Organelle (ii) The organelle which is responsible for the production and transport of lipids. Description (iii) Organelle (iii) onsists of thylakoid membranes. Site of photosynthesis. [3]
9 (d) Give two advantages of using a light microscope to view cells in preference to an electron microscope. Advantage 1... Advantage 2... [2] [Total: 10] Turn over
10 4 Water is an important biological molecule which has many functions, such as maintaining cell volume. (a) State two other functions of water as a biological molecule. 1... 2... [2] (b) Saline is a sterile solution of salt and water. Isotonic saline has a salt concentration similar to tears, blood plasma and other body fluids. It is frequently used in intravenous drips for patients who cannot take fluids by mouth or are in danger of dehydration. Use your knowledge of osmosis to describe and explain why isotonic saline is used to maintain the volume of each blood cell.... [4] [Total: 6]
11 5 In the UK, 1 in 14 men are diagnosed with prostate cancer. About 5 10% of prostate cancers diagnosed are hereditary. The prostate specific antigen (PSA) is a protein, made by the prostate gland, which naturally leaks into the blood. The PSA test is a blood test which measures the level of PSA in the blood. A high PSA level can be a sign of prostate cancer. Fig. 5.1 shows a flow chart of the PSA test. Step 1 Monoclonal antibodies against PSA are attached to a test plate. Step 2 A sample of blood plasma from a person is added to the plate. The monoclonal antibody will combine with the PSA in the plasma. Step 3 The plate is washed. A second antibody is added. This antibody has an enzyme attached to it. The second antibody binds to the PSA. Step 4 The plate is washed again. A colourless substrate is added which is converted to a coloured product by the enzyme. Fig. 5.1 (a) (i) Explain why the antibodies used in the PSA test must be monoclonal antibodies....... [1] (ii) Suggest why the prostate specific antigen binds to the antibody in Step 2.......... [2] Turn over
(iii) 12 The plate must be washed at the start of Step 4, otherwise unreliable results could be obtained. Suggest why results showing higher than normal levels of PSA could be obtained if the plate is not washed at the start of Step 4.......... [2] (b) Suggest two moral and/or ethical issues which a man with a family history of prostate cancer may consider before he takes the PSA test. 1... 2... [2] [Total: 7]
13 6 Scientists who work in pathology laboratories in hospitals may use a haemocytometer or a oulter counter to count the numbers of red blood cells and white blood cells in specific volumes of blood from different patients. (a) State one reason why a haemocytometer will only provide an estimate of the number of cells in a sample of blood.... [1] (b) State one disadvantage of using a oulter ounter to count cells in blood samples.... [1] (c) Scientists in pathology laboratories may also need to determine the actual dimensions of cells to help diagnose medical conditions. State the two pieces of equipment which the scientists would need to use, apart from a microscope, to determine the actual dimensions of cells. 1... 2... [1] (d) Suggest one difference that could be observed in cells from a cervical smear taken from a healthy patient, compared with cells taken from a cervical smear of a patient diagnosed with cervical cancer.... [1] [Total: 4] END OF QUESTION PAPER
14 ADDITIONAL ANSWER SPAE If additional space is required, you should use the following lined page(s). The question number(s) must be clearly shown in the margin(s)............................................................................
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