2025 NYJC H2 Bio 9744 P1 MS

NANYANG JUNIOR COLLEGE PRELIMINARY EXAMINATIONS Higher 2 CANDIDATE NAME MARK SCHEME CLASS BIOLOGY 9744/01 Paper 1 Multiple Choice 24 September 2025 1 hour Additional Materials: Multiple Choice Answer Sheet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluid. Write your name and CT on the Answer Sheet in the spaces provided unless this has been done for you. There are thirty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet. Read the instructions on the Answer Sheet very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. Calculators may be used. This document consists of 16 printed pages. [Turn over H

9744 / H2 Biology / 01 2 1 D 11 B 21 C 2 A 12 D 22 B 3 A 13 D 23 C 4 A 14 D 24 B 5 A 15 B 25 C 6 C 16 C 26 C 7 A 17 A 27 D 8 C 18 C 28 B 9 C 19 A 29 D 10 C 20 C 30 B

9744 / H2 Biology / 01 3 1 A cell is shown in the micrograph. Which statement explains how it is possible to identify the type of microscope used to produce the micrograph? A The nucleus is visible, so an electron microscope was used. B The endoplasmic reticulum is not visible, so a light microscope was used. C Chloroplasts are visible, so a light microscope was used. D Ribosomes are visible, so an electron microscope was used. 2 There is a theory that mitochondria and chloroplasts were originally free -living prokaryotes. It is thought that millions of years ago these free -living prokaryotes were taken into larger cells by endocytosis where, instead of being digested, they became functional organelles. Which features of mitochondria and chloroplasts support this theory? 1 Mitochondria and chloroplasts are surrounded by double membranes. 2 Mitochondria and chloroplasts have small, circular DNA. 3 Mitochondria and chloroplasts synthesise proteins. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

9744 / H2 Biology / 01 4 3 The graph shows how the rate of facilitated diffusion of substance X across a cell surface membrane changed as the concentration of substance X increased. All conditions, except for the concentration of substance X, were kept constant. Temperature was maintained at 15°C. Which statement about the rate of facilitated diffusion is correct? A The rate of facilitated diffusion of substance X at Q will increase if the temperature is increased to 20 °C. B The rate of facilitated diffusion of substance X at P will increase if the concentration of ATP is increased. C The rate of facilitated diffusion of substance X at Q will increase if the concentration of substance X is increased. D The rate of facilitated diffusion of substance X at P will increase if the length of time over which the rate is measured is increased. 4 A naturally occurring polysaccharide synthesised in a plant is a branched chain of -glucose. The straight parts of the molecule are linked by -1,6 glycosidic bonds with only a small number of branches which are linked by either an -1,3 glycosidic bond or an -1,4 glycosidic bond. Which polysaccharide has a structure most similar to that described? A amylopectin B amylose C cellulose D glycogen

9744 / H2 Biology / 01 5 5 The diagram shows how the alternating nature of -glucose monomers along a chain allows hydrogen bonds to form between consecutive monomers. Hydrogen bonds in cellulose affect the tensile strength (the ability to withstand pulling forces without breaking). How do the hydrogen bonds shown in the diagram help cellulose function as a suitable material for a cell wall? A The hydrogen bonds add additional tensile strength along individual cellulose molecules within the cell wall. B The hydrogen bonds create stronger crosslinks between adjacent cellulose molecules, adding to the tensile strength of the cell wall. C Stronger hydrogen bonds form between adjacent cellulose molecules, adding to the tensile strength of the cell wall. D Cellulose molecules within a cellulose microfibril have a stronger link between them, increasing the tensile strength of the cellulose microfibrils. 6 Which statement is correct for a non-competitive inhibitor? A The inhibitor binds to the active site of the enzyme and decreases Vmax. B The inhibitor binds away from the active site and increases the Michaelis–Menten constant. C The inhibitor decreases Vmax, but the Michaelis–Menten constant does not change. D The inhibitor does not change Vmax but increases the Michaelis–Menten constant.

9744 / H2 Biology / 01 6 7 A student carried out investigations at pH 1–8 to look at the effect of pH on an enzyme-catalysed reaction. The optimum condition for this enzyme is the acidic environment of the stomach at pH1–2. The remaining substrate concentration was measured after five minutes at each different pH. Which graph shows the effect of increasing pH on substrate concentration remaining after five minutes? AAAAAAAAAAAA

9744 / H2 Biology / 01 7 8 The diagrams show the chemical structure of four bases. Which diagrams show thymine and cytosine? A 1 and 2 B 1 and 4 C 2 and 3 D 3 and 4 9 The diagram shows the nucleotide sequence of a small section of the transcribed strand of a gene. GCG CGC GGC GCG The table shows the amino acids coded for by 10 mRNA codons. What is the sequence of the four amino acids in the polypeptide translated from this small section of a gene? A Ala-Ala-Cys-Ala B Ala-Arg-Gly-Ala C Arg-Ala-Pro-Arg D Arg-Arg-Thr-Arg

9744 / H2 Biology / 01 8 10 In an experiment, scientists hybridised an mRNA to its DNA template and prepared the hybrid molecule for electron microscopy. The resulting hybrid was observed to have different sections of DNA-RNA hybrids as well as single stranded DNA loops as in the diagram. Several statements attempting to explain the observations are presented: 1 Genes contain unique sequences within them that are not transcribed into mRNA. 2 DNA genes are not continuous and are interrupted by non-coding sequences. 3 Insertional mutations always disrupt genes and result in additional sequences. 4 mRNA undergoes processing to remove some of its sequences. How many statements correctly explain the findings? A 0 B 1 C 2 D 3

9744 / H2 Biology / 01 9 11 Circadian rhythm is the body's internal clock that regulates sleep and wake cycles over a 24-hour period. It is controlled by numerous proteins which regulate the cyclic nature of the rhythm. The roles of two such proteins are described here: • Circadian Locomotor Output Cycles Kaput (CLOCK): This protein forms a complex with another protein called Brain and Muscle ARNT-Like 1 (BMAL1) to initiate the transcription of target genes involved in the circadian rhythm. • Cryptochrome 1 (CRY1): Cryptochrome proteins play a role in the negative feedback regulation of the circadian rhythm. They interact with the CLOCK-BMAL1 complex to inhibit its action. Which row correctly describes the level at which the proteins regulate expression of genes responsible for circadian rhythm? CLOCK CRY1 A transcriptional translational B transcriptional post-translational C translational transcriptional D post-transcriptional post-translational 12 What are the correct roles of m