2024 VJC H2 Bio P3 QP

1 VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION 2024 HIGHER 2 NAME : ……………………………………………………….………………. CT CLASS: ………………..……… BIOLOGY Paper 3 Long Structured and Free-response Questions 9744 / 03 17/09/2024 2 hour Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name and CT class 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. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer any one question in the space 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 bracket [ ] at the end of each question or part question. Question Marks Section A 1 2 3 Section B Total This document consists of 24 printed pages. [Turn over]

2 Section A Answer all the questions in this section. 1 Thyroid hormones are produced and released by the thyroid gland. In humans, the thyroid gland is found in the neck below the Adam’s apple. It is lined with thyroid follicular cells, also called thyrocytes, that surround a lumen. Fig. 1.1 shows the thyroid follicular cells. Fig. 1.1 Unlike most hormones with specific target cells or tissues, the thyroid hormones act on nearly every cell in the body and are important in regulating the basal metabolic rate of the body. They regulate the metabolism of proteins, fat and carbohydrates in cells, affecting protein synthesis and cellular respiration. They are also involved in the control of heat generation in the body and are essential for proper cell development and differentiation. There are two types of thyroid hormones, namely triiodothyronine (T3) and thyroxine (T4). Their structures differ by the number of iodine present. Fig. 1.2 shows the structure of T3 and T4. Fig. 1.2

3 (a) With reference to Fig. 1.1 and 1.2, (i) suggest how thyroid hormones are able to act on nearly every cell in the body. …………………………………………………………………………………………………... …………………………………………………………………………………………..…… [1] (ii) compare the structure of thyroid hormones to an amino acid. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………..…… [2] (b) The release of thyroid hormones from the thyroid gland is regulated by other hormones released from the brain. Neurones in the hypothalamus in the brain release thyrotropin - releasing hormone (TRH), which stimulates the release of thyroid -stimulating hormone (TSH) from cells in the anterior pituitary. TSH then stimulates the rele