CJC 2023 JC2 Bio P1 (QP)

NAME: ___________________________________________ CLASS: _________ INDEX: __________ CATHOLIC JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION Higher 2 BIOLOGY 9744/01 Paper 1 Multiple Choice 18 September 2023 1 hour Additional Materials: Answer Sheet (Multiple Choice Optical Mark Sheet) READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name (as per NRIC), class, and index number on this booklet. Write and shade your name (as per NRIC) , NRIC / FIN number and class on the Answer Sheet (Multiple Choice Optical Mark Sheet) in the spaces provided. There are 30 multiple choice questions in 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 shade your choice in soft pencil on the Answer Sheet (Multiple Choice Optical Mark Sheet). 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 21 printed pages and 1 blank page [Turn over

2   2023 Prelim/ 9744/ 01 1 The diagram shows two electron micrographs of cells. F G Which organelles are visible in each of the cells F and G? Key:  = visible  = not visible cell chloroplasts nucleolus nucleus A F G       B F G       C F G       D F G      

3   2023 Prelim/ 9744/ 01 2 The figure below shows an electr on micrograph of a pair of barrel- shaped centrioles that play an important role in organising microtubules that serve as the cell’s skeletal system. They help determine the locations of the nucleus and other organelles within the cell. Microtubules are assembled from a heterodimeric protein called tubulin, as shown in the diagram below. Which of the following explains why tubulin is considered a polymer as well as a monomer? why tubulin is a polymer why tubulin is a monomer A It is a macromolecule. It is a quaternary protein. B It is the building block of microtubule. It is made up of many amino acids. C It is made up of many amino acids. It is the building block of microtubule. D It has many α-helices and β-pleated sheets. It is made up of two different subunits. microtubule  α‐tubulin  β‐tubulin  centrioles

4   2023 Prelim/ 9744/ 01 3 One way of representing fatty acid chains is Cx : y, where Cx is the number of carbon atoms and y is the number of double bonds. The table shows the percentage mass of eight different fatty acid chains in four cell membranes, 1, 2, 3 and 4. Cell Membrane percentage mass of each fatty acid chain C10 : 0 C12 : 0 C14 : 0 C16 : 0 C18 : 0 C18 : 1 C18 : 2 C18 : 3 1 1 2 2 21 35 29 2 1 2 2 23 19 45 3 1 3 2 3 23 21 43 4 4 1 2 4 22 2 52 11 1 Which of the following about the four cell membranes ( 1, 2, 3 and 4) is correct? Most fluid Least fluid A 1 2 B 2 3 C 3 4 D 4 1

5   2023 Prelim/ 9744/ 01 4 Protein X is found in the common bean, Phaseous vu/garis . This protein decreases the activity of amylase in the gut of some insect pests. Protein X also acts as a chitinase enzyme that br eaks down chitin. Chitin is a polysaccharide found in the cell walls of fungi. Protein X has no other enzymatic activity. Which conclusions are consistent with this information? 1 X has a complementary shape to starch allowi ng it to block the active site of amylase. 2 The active site of X is complementar y in shape to chitin and also to amylase. 3 The presence of X can reduce the energy av ailable to insects that feed on this plant. 4 X could protect this plant from attack by fungi. A All of the above. B 1, 3 and 4 C 1 and 2 D 3 and 4 5 Molecules and ions can cross membranes by a number of different mechanisms. Which row shows possible mechanisms by which each molecule or ion can cross the cell surface membrane? glycosylated enzyme glucose hydrogen ions carbon dioxide A diffusion and exocytosis facilitated diffusion active transport and facilitated diffusion diffusion B endocytosis diffusion and facilitated diffusion active transport and diffusion diffusion and facilitated diffusion C exocytosis active transport and facilitated diffusion active transport and facilitated diffusion diffusion D facilitated diffusion and endocytosis facilitated diffusion diffusion and facilitated diffusion facilitated diffusion

6   2023 Prelim/ 9744/ 01 6 Stem cells can be used to replace cells in damaged tissues, such as skin. The diagram shows two ways in which replacement skin cells can be produced. Which row correctly describes the stem cells P, Q and R? P Q R A pluripotent multipotent totipotent B pluripotent induced pluri potent induced pluripotent C totipotent pluripotent induced pluripotent D totipotent totipotent totipotent

7   2023 Prelim/ 9744/ 01 7 A research student wanted to replicate the Meselson and Stahl experiment. He selected cells of the bacterium E. coli that have been grown for many generations on a medium containing only the heavy isotope of nitrogen ( 15N) and transferred these cells to a medium containing only 14N to grow. Samples of the bacteria were removed from the culture after one generation and the DNA from the samples was extracted and centrifuged. The results are illustrated in the diagram below: The student then replated by transferring the remain ing bacteria onto 2 new petri dishes of growth medium and allowed them to grow for 2 generations. Samples were taken from each of the 2 petri di shes and DNA was extracted and centrifuged in 2 separate tubes, tube X and tube Y which showed different results. The student suspected that there might have been a mixed up in the growth medium in the 2 petri dishes used for the replating. Instead of both containing 14N only, the growth medium in one of the petri dishes might contain 15N only. He analysed the results from tube X and tube Y and concluded that the DNA in tube Y came from bacteria cells that have been replated and grown on medium containing 15N. What are the positions and relative proportions of the bands in both tube X and tube Y? Tube X Tube Y Upper Middle Lower Upper Middle Lower A 0% 25% 75% 25% 75% 0% B 50% 50% 0% 0% 50% 50% C 50% 0% 50% 0% 75% 25% D 75% 25% 0% 0% 25% 75%

8   2023 Prelim/ 9744/ 01 8 Transfer RNA combined with an amino acid is called amino-acyl tRNA. It is possible to chemically convert the amino acid cysteine into the amino acid alanine whilst it is still attached to its tRNA. The altered amino-acyl tRNA still binds to UGU triplets on messenger RNA (mRNA), but now incorporates alanine into the resulting polypeptide instead of cysteine.   Which statement is correct? A A codon on the amino-acyl tRNA determines its specificity. B Both the amino acid and the anticodon of an ami no-acyl tRNA affect where it binds to mRNA. C The amino acid of an amino-acyl tRNA does not influence its binding to mRNA. D The codon-anticodon interaction is influenced by the amino acid on an amino-acyl tRNA. 9 RNA interference (RNAi) is a natural cellular proc ess that silences gene ex pression by p