Woodgrove T3W2 4E Pure Biology Prelim 2023 paper2 updated

1 Name Index Number Class O LEVEL PRELIMINARY EXAMINATION 2023 LEVEL & STREAM : Four (Express) SUBJECT (CODE) : Biology ( 6093 ) PAPER NO : 2 DATE (DAY) : 12 September 2023 ( Tuesday ) DURATION : 1 h 45 mins READ THESE INSTRUCTIONS FIRST Write your class, index number and name on the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions in the spaces provided. Section B Answer all the questions, the last question is in the form either/or. Write your answers in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. You are advised to spend no longer than one hour on Section A and no longer than 45 minutes on Section B. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section Marks A /50 B /30 Student’s Signature Parent’s Signature Total /80 Date Date This document consists of 20 printed pages including this cover page Setter : Miss Ng Shuwen

2 Section A Answer all questions. Write your answers in the spaces provided on the question paper. 1 Fig. 1.1 shows a section through part of a dicotyledonous a leaf when viewed using a light microscope. Fig. 1.1 (a) (i) State the term used to describe a group of cells, such as those in part A or part B of the leaf cross-section. __________________________________________________________ [1] A B

3 (ii) Fig. 1.2 shows an enlargement of one cell from part A of the leaf section. Fig. 1.2 Complete Fig.1.2 by drawing and labelling to show the position of • one chloroplast • three other types of named cell component that will be visible. [4] (iii) On Fig.1. 1, label and name one cell in the lower epidermis that would also contain chloroplasts. [1] (b) Explain how Part B is adapted to facilitate transpiration in this leaf. _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ [4] cell wall

4 2 Microorganisms such as bacteria are used in the production of yogurt. Under anaerobic condition s, bacteria will break down lactose in milk to release energy, with carbon dioxide and lactic acid produced as by-products. Fig. 2.1 shows how the concentration of lactose changes during the formation of yoghurt from milk over a period of 48 hours. Fig. 2.1 (a) State one similarity and o ne difference between the an aerobic respiration process in bacteria and in muscle cell in human. Similarity ______________________________________________________ _______________________________________________________________ Difference _____________________________________________________ _______________________________________________________________ [2] time / h concentration

5 (b) Describe the graph shown in Fig. 2.1. _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ [2] (c) Describe how you could test for the presence of lactose at t = 0. _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ [2] (d) Lactose intolerance is a medical condition that results from a genetic change. A person with the condition is unable to produce molecules of the correct enzyme to digest lactose. (i) Name this type of genetic change and explain how it can result in a person being unable to produce molecules of the correct enzyme and to digest lactose. __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ [3]

6 (ii) Using Fig. 2.1, suggest and explain if yoghurt makes it a better food than milk for a person with lactose intolerance. __________________________________________________________ __________________________________________________________ __________________________________________________________ [2] 3 The human liver contains a high concentration of enzymes called transaminases. These enzymes are important in the metabolism of amino acids. Amino acids are absorbed into the villi in the small intestine and carried to th e liver by a blood vessel. Fig. 3.1 shows a villus. Fig. 3.1 (a) (i) Identify structure A and B, and explain how they are adapted to absorption of digested food substances: Structure A : _____________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________

7 Structure B : _____________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ [4] (ii) Name a tissue that has similar structural adaptations as villus. __________________________________________________________ [1] (b) (i) Describe how excess amino acids are metabolised and excreted. __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ [3] (ii) State one other role of the liver. __________________________________________________________ [1] (c) There are different types of transaminase. Each type has a specific active site. Explain why this means that each type catalyses a specific reaction. _______________________________________________________________ _________________________________________________