2025 JC2 TJC Prelim P1 ANS

1 [Turn over TEMASEK JUNIOR COLLEGE 2024 JC2 PRELIMINARY EXAMINATION Higher 2 BIOLOGY 9744/01 Paper 1 Multiple Choice 18 September 2025 1 hour Additional Materials: Multiple Choice Answer Sheet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, civics group and index number on the Answer Sheet in the spaces provided. Do not open this booklet until you are told to do so. 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. The use of an approved scientific calculator is expected, where appropriate. This document consists of 18 printed pages and 2 blank pages.

2 1 A scientist carried out an experiment to separate cell structures in animal cells. The cells were broken open to release the cell structures. This extract was filtered into a centrifuge tube and then spun in a centrifuge. The heaviest cell structure sank to the bottom forming pellet 1. The liquid above pellet 1 was poured into a clean centrifuge tube and spun in the centrifuge at a higher speed to separate the next heaviest cell structure. This cell structure sank to the bottom, forming pellet 2. This procedure was repeated twice more to obtain pellet 3 and pellet 4, each containing a single type of cell structure. Which row shows the order in which the cell structures were collected? pellet 1 pellet 2 pellet 3 pellet 4 A nucleus lysosomes mitochondria ribosome B nucleus mitochondria lysosomes ribosomes C ribosomes lysosomes mitochondria nucleus D ribosomes mitochondria lysosomes nucleus 2 The electron micrograph shows part of two cells. Which labelled features identify these cells as eukaryotic? A W, X and Y B W and X only C W only D X only

3 [Turn over 3 Batrachotoxin is a poison found in frogs in the Columbian jungle. The poison is used by Native Indians to produce poison darts. The poison works by increasing the permeability of some cell surface membranes to sodium ions, which move out of the cells. Which statements are correct for cells affected by batrachotoxin? 1 The intracellular fluid has a higher water potential than the extracellular fluid. 2 The extracellular fluid has a higher water potential than the intracellular fluid. 3 Water leaves the cells by osmosis, causing the cells to shrink. 4 Water enters the cells by osmosis, causing the cells to swell. A 1 and 3 B 1 and 4 C 2 and 3 D 2 and 4 4 The diagrams show short sections of some common and modified polysaccharides. Which statement is correct? A 1 is found in cellulose as β-1,4-glycosidic bond is present. B 2 is found in amylopectin, which is a helical molecule, allowing for extensive coiling and entangling. C 3 is found in cellulose, which is an unbranched and straight chain of β-glucose monomers. D 4 is found in glycogen, which is made of chains of α-glucose linked by α-1,4-glycosidic bonds and a α-1,6-glycosidic bonds at the branches.

4 5 The diagram shows a protein molecule. Two long polypeptides each form α-helices for much of their length and these twist together into a fibre. At one end, each of these polypeptides coils into a globular head. Two short polypeptides bind to each head. What describes the protein structure of this molecule? A quaternary structure because each molecule consists of six polypeptides B secondary structure because the long polypeptides form α-helices C tertiary structure because the α-helices form a fibre D tertiary structure because the heads form globular proteins 6 A species of bacterium, Streptococcus salivarius, produces an enzyme, FruA, which digests complex sugars. The fungus Aspergillus niger secretes a different FruA with a different molecular weight, which is encoded by a different gene. How can these different FruA enzymes digest the same complex sugars in the same way? A Both FruA enzymes have the same primary structure. B The enzyme-substrate complexes formed by both enzymes are identical. C The FruA enzymes both have the same tertiary structure. D The parts of the primary structure forming the active site are the same in both enzymes.

5 [Turn over 7 The graph compares the effect of temperature on the activity of the protease enzyme, papain, when in solution (free) and when immobilised in alginate beads. Which statement about the effect of immobilisation of papain is correct? A It alters the shape of papain’s active site at higher temperatures. B It decreases the activity of papain at higher temperatures. C It increases the stability of papain at higher temperatures. D It reduces the number of collisions of papain with the substrate.

6 8 An experiment was conducted to investigate the use of a new carbohydrate source (substance L) for the production of ethanol as biofuel. The aim was to find the optimum length of time to leave a mixture of yeast and substance L to produce ethanol. An airtight container containing yeast and substance L was set up and the concentrations of oxygen, carbon dioxide and ethanol were measured over 10 hours. The results of the experiment are shown in the graph. Which statement is consistent with the results? A Amount of ethanol increased because there was insufficient supply of the hydrogen carrier NAD + as the reaction proceeded. B Anaerobic respiration occurred two and a half hours into the experiment and the mixture should be left for seven hours. C High rate of glycolysis resulted in higher rate of anaerobic respiration as seen by an increase in carbon dioxide concentration. D Substance L is a good carbohydrate source as the amount of ethanol produced remains relatively high even after several hours into the experiment.

7 [Turn over 9 Different types of reactions occur in the Calvin cycle. Which statement correctly describes Calvin cycle? A Carboxylation occurs in the conversion of triose phosphate to ribulose bisphosphate. B Decarboxylation occurs in the conversion of ribulose bisphosphate to 3-phosphoglycerate. C High rate of glycolysis resulted in higher rate of anaerobic respiration as seen by an increase in carbon dioxide concentration. D Reduction occurs in the conversion of 3-phosphoglycerate to glyceraldehyde-3-phosphate. 10 Cell division is the means of almost all growth and reproduction. Which graph correctly represents a form of cell division that maintains genetic stability at the expense of variation? Ans: A 11 Which property of embryonic stem cells makes them particularly useful in medical research? A They can be fused together to form a zygote. B They can divide and are pluripotent. C They can divide and are totipotent. D They can continue to divide indefinitely.

8 12 Which statement is correct? A During transcription, mRNA is synthesised from DNA nucleotides to have the same sequence of nucleotides as the DNA strand on which it was made. B During transcription, tRNA is synthesised from RNA nucleotides and carries codons that are complementary to the sequence of nucleotides on the DNA strand on which it was made. C During translation, mRNA is synthesised from RNA nucleotides to have the complementary sequence of nucleotides to that of the DNA strand on which it was made. D During translation, ribosomes join amino acids