RVHS- PRELIM- 9744-2024 JC2 H2 Prelim P3 MS

RIVER VALLEY HIGH SCHOOL JC 2 PRELIMINARY EXAMINATION CANDIDATE NAME CENTRE NUMBER S CLASS 23J INDEX NUMBER BIOLOGY 9744/03 Paper 3 Long Structured and Free-response Questions 13 September 2024 2 hours Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, index number and name in the spaces at the top of this page. 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. DO NOT WRITE ON ANY BARCODES. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer any one question in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 2 3 Section B Total This document consists of 23 printed pages and 1 blank page.

2 River Valley High School H2 Biology 9744/03 2024 JC2 Preliminary Examination Section A Answer all the questions in this section. 1 Thyroid hormones, such as thyroxine, play crucial roles in regulating metabolism and brain development. Fig 1.1 shows how the thyroid -stimulating hormone (TSH) from the pituitary gland stimulates the thyroid follicle cell to produce thyroxine. Fig. 1.1 (a) Name the receptor type to which TSHR belongs and describe the role of protein kinases in stage A. [3] 1. G-protein coupled receptor;; 2. protein kinases transfer phosphate group (from ATP) to substrate (other protein kinases); 3. inducing conformational change; 4. of substrate into its active form; 5. initiating phosphorylation cascade / within a phosphorylation cascade; AO A key TSHR – thyroid-stimulating hormone receptor TG – thyroglobulin DUOX2 – dual oxidase 2 enzyme

3 River Valley High School H2 Biology 9744/03 2024 JC2 Preliminary Examination 6. allows for signal amplification; 7. max 3 Congenital hypothyroidism (CH) is a common endocrine metabolic disease caused by insufficient thyroxine secretion in a patient at birth. In a genetic study on CH, blood samples of patients were analysed and two gene mutations associated with the disease were identified. The results for a healthy individual and two patients with CH are shown in Table 1.1. The partial gene sequences shown are found at the start of each gene. Table 1.1 individual blood TSH / mU L-1 partial gene sequence TSHR locus (triplets 4 to 6) DUOX2 locus (triplets 6 to 10) healthy <15.0 3’-TAGTGGCAT-5’ 3’-TGCACCGACTCTATA-5’ patient 1 44.3 3’-TAGTCGCAT-5’ 3’-TGCACCGACTCTATA-5’ patient 2 >50.0 3’-TAGTGGCAT-5’ 3’-TGCACTGACT