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Year 12 Biology: Intervention booklet. Name ………………………………………. This booklet needs to be fully completed and brought to the intervention session at 2:45 on Friday 11th November. The session will be 1 hour. You should attempt the booklet open book using your notes and textbook to help. Answer in bullet points 1 point for each mark. 1. The diagram shows a triglyceride molecule. H O Fatty acid 1 H C O C O Fatty acid 2 H C O C O Fatty acid 3 H C O C H A (a) Name part A. .................................................................................................................................... (1) (b) With reference to named parts of the diagram, explain the difference between the terms: (i) triglyceride and phospholipid; .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... (2) (ii) saturated and unsaturated. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... (2) (Total 5 marks) West Bridgford School 1 2. Read the following passage. During the course of a day, we come into contact with many poisonous substances. These include industrial and household chemicals. The skin acts as a barrier and prevents many of these substances entering and harming the body. 5 The skin is one of the largest organs in the body. It is composed of several layers of tissue. The outer layer consists of dead cells packed with keratins. Keratins are a group of proteins that differ from each other in their primary structure. Each keratin molecule consists of several polypeptide chains, each individual chain wound into a spiral or helix. The polypeptide chains include many sulphur-containing amino acids and these help to give the keratin molecules their characteristic strength. Use information from the passage and your own knowledge to answer the questions. (a) What is the evidence from the passage that keratin molecules have a quaternary structure? ..................................................................................................................................... ..................................................................................................................................... (1) (b) Explain how sulphur-containing amino acids help to give keratin molecules their characteristic strength (lines 8–9). ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (c) Explain why differences in primary structure result in keratins with different properties (line 6). ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (d) The skin prevents poisonous substances entering and harming the body (line 3). Explain why these substances are unable to pass through the outer layer of skin cells by active transport. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) West Bridgford School 2 (e) Skin cells may be studied with a transmission electron microscope or an optical microscope. Explain the advantages and limitations of using a transmission electron microscope to study cells. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (6) (Total 14 marks) 3. (a) Cylinders of potato were cut using a cork borer. Each cylinder was placed into one of a range of sucrose solutions of different concentrations. The cylinders were left for 6 hours and then removed from the solutions. The mass of each cylinder was recorded before and after immersion. The graph shows the results of this investigation. +10 Increase Percentage change in 0 mass 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Concentration of sucrose / mol dm –3 Decrease –10 (i) Explain why the change in mass was given as a percentage change. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) West Bridgford School 3 (ii) Explain the shape of the curve as the concentration of sucrose decreases from 0.3 mol dm–3 to 0.1 mol dm–3. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (4) (iii) What concentration of sucrose solution is equivalent to the mean water potential of the potato cells? Explain your answer. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (b) The diagram represents three plant cells and shows the water potential of two of these cells. The arrows show the direction of water movement between these three cells. A –510 kPa B C –550 kPa Suggest the range of possible values for the water potential of cell B. Explain your answer fully. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (2) (Total 10 marks) West Bridgford School 4 4. The diagram shows part of a plant cell as seen through an electron microscope. (a) Name organelles A, B and C. A ................................................................... B ................................................................... C ................................................................... (3) (b) Give the function of (i) structure X; .......................................................................................................................... .......................................................................................................................... (ii) structure Y. .......................................................................................................................... .......................................................................................................................... (2) (c) Calculate the width of the structure labelled X in micrometres. Show your working. Width ............................ micrometres (µm) (2) (Total 7 marks) 5. Mitochondria were isolated from the liver tissue using differential centrifugation. The tissue was West Bridgford School 5 chopped in cold, isotonic buffer solution. A buffer solution maintains a constant pH. The first stages in the procedure are shown in the diagram. Tissue chopped in cold isotonic buffer solution Homogenised Stage 1 Stage 2 (i) Centrifuged al low speed for 10 minutes Stage 3 The tissue was chopped in cold, isotonic buffer solution. Explain the reason for using a cold solution; ............................................................................................................ ..................................................................................................................................... an isotonic solution; .................................................................................................... ..................................................................................................................................... a buffer solution. ......................................................................................................... ..................................................................................................................................... (3) (ii) Why is the liver tissue homogenised? ..................................................................................................................................... ..................................................................................................................................... (1) (iii) Describe what should be done after Stage 3 to obtain a sample containing only mitochondria. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 6 marks) West Bridgford School 6 6 The diagram shows the arrangement of protein molecules in part of a cell surface membrane. Key Protein (a) Explain how amino acid molecules may be linked to form a polypeptide chain which is folded into a specific tertiary shape. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (6) (b) Describe the role of proteins in the transport of molecules and ions across cell surface membranes. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (7) (c) The hormone glucagon is a protein. It targets liver cells but does not affect other cells in the body. Explain why. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (4) (Total 17 marks) West Bridgford School 7 7. Six cylinders of a standard size were cut from a single large potato. One cylinder was placed in distilled water and the others were placed in sucrose solutions of different concentrations. The length of each cylinder was measured every 5 minutes for the next 50 minutes. The graph shows the changes in length at each sucrose concentration. +5 Distilled water +4 Decrease +3 +2 0.2 mol dm –3 +1 Change in length /mm 0 10 20 30 40 50 Time / minutes –1 0.4 mol dm –3 –2 –3 0.6 mol dm –3 Increase –4 0.8 mol dm –3 –5 (a) 1.0 mol dm –3 Explain why (i) the potato cylinder in distilled water increased in length; ......................................................................................................................…. ......................................................................................................................…. ......................................................................................................................…. ......................................................................................................................…. (2) (ii) the potato cylinder in the 1.0 mol dm–3 sucrose solution showed no further decrease in length after 40 minutes. ......................................................................................................................…. ......................................................................................................................…. ......................................................................................................................…. ......................................................................................................................…. (2) West Bridgford School 8 (b) (i) Describe the difference in the rate of decrease in length during the first 10 minutes between the cylinder in the 0.4 mol dm–3 and the cylinder in the 0.8 mol dm–3 solution. ......................................................................................................................…. ......................................................................................................................…. (1) (ii) Use your knowledge of water potential to explain this difference. ......................................................................................................................…. ......................................................................................................................…. (1) (c) After 45 minutes the potato cylinder in the 0.8 mol dm–3 solution was removed and blue dye added to this solution. Some of this blue-stained solution was drawn into a syringe. A drop was then released, slowly, halfway down a test tube of fresh 0.8 mol dm–3 sucrose solution as shown in the diagram. The blue drop quickly moved to the surface of the liquid in the test tube. Syringe needle Blue drop 0.8 mol dm –3 sucrose solution (i) The density of a solution depends on its concentration. The more concentrated the solution the greater its density. Explain why the blue drop had a lower density and therefore moved up. ......................................................................................................................…. ......................................................................................................................…. ......................................................................................................................…. ......................................................................................................................…. (2) (ii) A sucrose solution of concentration 0.3 mol dm–3 has a water potential which is equivalent to that of the potato cells. Describe and explain what would happen to the blue drop from this solution. ......................................................................................................................…. ......................................................................................................................…. ......................................................................................................................…. (2) (Total 10 marks) West Bridgford School 9