2022 J2 ASRJC H2 Biology Paper 1 (with answer)

ASRJC BIOLOGY DEPT 9744/2022/J2MYCT/P2/B [Turn over 2022 JC2 PRELIMINARY EXAMINATIONS BIOLOGY 9744/01 PAPER 1 20 SEPTEMBER 2022 MULTIPLE CHOICE TUESDAY WORKED SOLUTIONS 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, class and identification number on the MCQ Answer Sheet. 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. 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 scientific calculators is expected, where appropriate. This document consists of 19 printed pages. H2 ANDERSON SERANGOON JUNIOR COLLEGE HIGHER 2

2 ASRJC BIOLOGY DEPT 9744//2022/J2PRELIMS/P1 1 Four students, A, B, C and D, observed a root hair cell from a plant using an electron microscope. They were asked to confirm the presence or absence within the cell of described cellular structures. Which student made the correct set of observations? area near the nucleus containing a pair of structures that are composed of microtubules centrioles a network of tubes and sacs with each tube and sac (cisterna) bounded by a single membrane (smooth) endoplasmic reticulum a stack of elongated, curved sacs with each sac (cisterna) bounded by a single membrane Golgi body structure with a double membrane containing stacks of flattened sacs (thylakoids) chloroplast Centrioles are only found in animal cells but not in higher plant cells. (Higher pants are plants that have specialised tissues for conducting water, minerals, and photosynthetic products through the plant. In contrast, lower plants do not have roots and produce spores to reproduce, rather than flower Found in a typical eukaryotic cell Found in a typical eukaryotic cell Present in eukaryotic photosynthetic cells e.g. leaf cells. Root hair cells do not undergo photosynthesis. A ✓ × × ✓ B × ✓ ✓ ✓ C × ✓ ✓ × D ✓ ✓ × × ✓= present × = absent

3 ASRJC BIOLOGY DEPT 9744//2022/J2PRELIMS/P1 [Turn over 2 Which statement provides evidence that viruses are not living organisms, according to the cell theory? A Complete viruses are assembled from components synthesised within cells, such as proteins and nucleic acids. This statement seems to suggest that viruses are living organisms since they are made up of same biomolecules as living organisms & does not give the idea of acellular; B is the better answer B During some stages of the reproductive cycle of a virus, the virus may only be present as nucleic acids. We can infer that virus does not have a cellular organisation as it exists just as RNA/DNA C Many viruses are smaller than the smallest prokaryotic cells. While this statement is true on its own, size is not a criteria to decide whether something is living or non-living. Size also does not relate to cell theory, thus this does not suggest viruses are non-living D Viruses lack internal membranes such as endoplasmic reticulum. Bacteria cells also lack internal membrane, but they are still living. So having/ not having internal membrane is not a criteria to decide whether something is living or non-living. Internal membranes also does not relate to cel l theory, thus this does not suggest viruses are non - living Many candidates selected the incorrect options A and C. In evaluating the options, the key aspect of the cell theory that these candidates had overlooked was that all cells come from pre-existing cells. The Cell Theory states that: (a) Cells are the smallest, basic unit of life. It is the basic unit of structure and function in all living organisms and is three-dimensional in nature. (b) All organisms are made of cells . Living organisms can be unicellular, consisting of a single cell, or complex, multicellular organisms, consisting of billions of cells. (c) All cells come from pre -existing cells via cell division and involves the passing of hereditary information encoded in DNA from one generation to the next.

4 ASRJC BIOLOGY DEPT 9744//2022/J2PRELIMS/P1 3 Four types of structure found in biomolecules are shown. Which row shows an example of a biomolecule in which each of these types of structure may be found? unsaturated fatty acid saturated fatty acid phospholipid triglyceride A 2 1 4 3 B 3 1 2 4 C 3 4 2 1 D 4 3 1 2 Explanation • 1 – saturated hydrocarbon, 2 – unsaturated hydrocarbon, 3 – carboxylic acid, 4 – ester bond • Unsaturated FA may contain 1, 2, 3 • Saturated FA may contain 1 and 3 • Phospholipid may contain 1, 2 and 4 • Triglyceride may contain 1, 2, 4. Triglyceride cannot be 3 because the COOH groups of the fatty acid chains are used to form ester bonds • Use elimination method, B is the best answer

5 ASRJC BIOLOGY DEPT 9744//2022/J2PRELIMS/P1 [Turn over 4 A peptide section of an insulin molecule was hydrolysed by two proteases, trypsin and chymotrypsin. • Trypsin breaks the peptide bonds at the carboxyl terminals of lysine (lys) and arginine (arg). • Chymotrypsin breaks the peptide bonds at the carboxyl terminals of phenylalanine (phe), tryptophan (trp) and tyrosine (tyr). The hydrolysis was performed separately using: i. both enzymes, or tyr- leu-val-cys-gly-glu-arg -gly-phe -phe -tyr -thr-pro-lys- ala 7 fragments, each fragment between 6 and 1 a.a ii. trypsin only, or tyr-leu-val-cys-gly-glu-arg -gly-phe-phe-tyr-thr-pro-lys -ala 3 fragments, each fragments are either 7 or 1 a.a iii. chymotrypsin only. Tyr -leu-val-cys-gly-glu-arg-gly-phe- phe -tyr -thr-pro-lys-ala 5 fragments, each fragment between 8 and 1 a.a, ie 2 fragments & 3 a.a The sequence of amino acid residues in the peptide is shown below: (amino terminal) tyr-leu-val-cys-gly-glu-arg-gly-phe-phe-tyr-thr-pro-lys-ala (carboxy terminal) Which statement concerning the products of hydrolysis is correct? A Fewer than half of the fragments from hydrolysis (i) are single amino acids. Not true because 4 out of 7 are single amino acids. B Hydrolysis (ii) yields one fewer fragment than hydrolysis (iii). Not true because hydrolysis (ii) yields two fragment fewer than hydrolysis (iii). C Hydrolysis (ii) yields one more dipeptide than hydrolysis (iii). Not true because both hydrolysis (ii) & (iii) have no dipeptide. A dipeptide is two amino acid long. D With hydrolysis (i), all fragments formed are seven or fewer amino acid