NYJC Prelim 9744 Paper 1 Answer

NANYANG JUNIOR COLLEGE PRELIMINARY EXAMINATIONS Higher 2 CANDIDATE NAME MARK SCHEME CLASS BIOLOGY 9744/01 Paper 1 Multiple Choice 17 September 2024 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 20 printed pages.

2 [Turn over 1 Dialysis (Visking) tubing is an artificial partially permeable membrane with pore sizes of approximately 2.5 nm. Glucose molecules have a diameter of about 1.5 nm and can pass through the pores in the membrane. What else can pass through the pores? 1 bacteria 2 haemoglobin 3 ribosomes 4 fructose A 1 and 3 B 2 and 4 C 2 only D 4 only 2 Which statements are correct for chloroplasts and also for mitochondria? 1 They contain 80S ribosomes. 2 They can transcribe their circular DNA. 3 They can translate mRNA. 4 They are enclosed by double membranes. A 1, 2, 3 and 4 B 1 and 2 only C 2, 3 and 4 only D 3 and 4 only 9744 / H2 Biology / 01

3 3 The diagrams show three examples of different bonds. Which bond(s) hold(s) the secondary structure of proteins together? A 1, 2 and 3 B 1 and 3 only C 1 only D 2 and 3 only 4 A student was provided with a solution of carbohydrate. They removed two samples from the solution and performed tests on each sample, as shown. Which statement explains the results? A Condensation reactions occur in sample two to release reducing sugar. B Glycosidic bonds in a polysaccharide have been broken to release reducing sugar. C Sample one shows that sucrose is present in the carbohydrate solution. 9744 / H2 Biology / 01

4 D The change in colour to a yellow solution shows that glucose is present. 5 Influenza virus has an enzyme called neuraminidase which breaks down glycoproteins in the surface membrane of the cell that the virus will infect. The glycoprotein binds to the active site of neuraminidase by induced fit. Which statements about the induced fit hypothesis of enzyme action are correct? 1 The active site must have the same shape as the substrate for them to bind together. 2 This enzyme is less likely to be affected by non-competitive inhibitors than an enzyme working by the lock-and-key mechanism. 3 The substrate is converted to product by specific R-groups in the active site just like the lock-and-key mechanism. A 1 and 2 only B 2 and 3 only C 2 only D 3 only 6 The diagram shows a metabolic pathway controlled by end product inhibition. Eight enzymes, E1 to E8 were used. As the concentration of the end product increases above a set level, an enzyme in the pathway leading to the end product is inhibited. An increase in the concentration of end product X does not lead to a decrease in the synthesis of end-product Y. Identify the enzyme that is inhibited by an increase in end-product X. A E1 B E2 C E3 D E6 9744 / H2 Biology / 01

5 7 Which row describes some properties of stem cells? 8 The following diagram shows some of the steps in the production of a protein within a cell. Which one of the following is a correct statement? A Step 1 represents translation. B There are six introns in the gene. C RNA polymerase is required for Step 3. D The circle on molecule F represents a modified guanine molecule. 9744 / H2 Biology / 01 able to divide by mitosis to produce more stem cells able to differentiate into specialised cells able to repair damaged cells Key ✔ = is a property = is not a property A ✔ ✔ ✔ B ✔ ✔ C ✔ D ✔

6 9 The table below shows the role of four different proteins involved in DNA replication. protein helicase topoisomerase single-strand binding protein DNA polymerase role unwinds the parental DNA double helix breaks and rejoin the DNA strands binds to separated DNA strands to stabilize them synthesises strand of DNA Which shows the function of these proteins? 10 What is an example of translational control of gene expression? A activation of proteins by folding or enzymatic cleavage B addition of chemical groups, such as phosphate groups, to free amino acids in the cytoplasm C binding of protein factors to specific sequences in mRNA preventing ribosomes attaching D formation of disulphide bridges in the protein being formed 9744 / H2 Biology / 01 helicase topoisomerase single-strand binding protein DNA polymerase A adds DNA nucleotides to the 3’ end of a growing polynucleotide strand prevents original strands reforming complementary base pairs enables tension caused by unwinding to be released makes strands available as templates B enables tension caused by unwinding to be released prevents original strands reforming complementary base pairs makes strands available as templates adds DNA nucleotides to the 3’ end of a growing polynucleotide strands C enables tension caused by unwinding to be released makes strands available as templates adds DNA nucleotides to the 3’ end of a growing polynucleotide strands prevents original strands reforming complementary base pairs D Makes strands available as templates enables tension caused by unwinding to be released prevents original strands reforming complementary base pairs adds DNA nucleotides to the 3’ end of a growing polynucleotide strands

7 11 A biopsy was conducted on breast cancer patients to extract samples of cancer cells. DNA from these sample cells were isolated and treated with DNase I, an enzyme that degrades histone-free DNA in a non-specific manner. After digestion, the DNase I was removed. Any remaining intact DNA was extracted, made single stranded and mixed with radioactively labelled DNA probes specific for these genes. Sample DNase I treatment Gene specific to radioactive DNA probes % binding of radioactive DNA to remaining DNA after DNase I digestion 1 No PTEN gene 90 2 Yes PTEN gene 19 3 No BRCA gene 88 4 Yes BRCA gene 87 Which of the following conclusions may be drawn from the results shown above? A PTEN and BRCA genes are both tumor suppressor genes.