2018 J2 HCI H2 Biology Prelims (w/ans)

2 © Hwa Chong Institution 2018 9744 H2 Biology / JC2 Preliminary Examinations / Paper 1 1 The electron micrographs 1, 2 and 3 show three different types of cells. Which row is correct? electron micrograph of cell type organelle found in cell type description of organelle A 1, 2 and 3 ribosomes embedded on the smooth endoplasmic reticulum for synthesis of polypeptides B 1 and 2 only vacuoles membrane-bound fluid-filled sacs C 3 only nucleoli dense masses within the nuclei D 2 only centrioles found in animal cells but absent in plant cells 1 2 3

3 © Hwa Chong Institution 2018 9744 H2 Biology / JC2 Preliminary Examinations / Paper 1 2 An investigation into the properties of an agent that causes a plant disease was carried out. The process was repeated several times and each successive group of plants developed the disease to the same extent as earlier groups. Which statements, supporting the idea that the infectious agent is a virus, can be concluded from the experiment? 1 Viruses cannot replicate outside of a host cell. 2 Viruses are smaller than bacterial cells and can pass through a bacterium-trapping filter. 3 Viruses can replicate within plant cells, so their ability to cause disease remains undiluted after several transfers from one healthy plant to another. A 1 only B 1 and 2 C 2 and 3 D 1, 2 and 3 3. Filtered sap was rubbed onto the leaves of healthy plants. 4. Healthy plants became infected 1. Sap was extracted from a diseased plant. 2. Sap was then passed through a porcelain filter known to trap bacteria.

4 © Hwa Chong Institution 2018 9744 H2 Biology / JC2 Preliminary Examinations / Paper 1 3 In an experiment, potato cylinders were placed in sucrose solutions of different concentrations. The potato cylinders were measured before and after immersion into each sucrose solution. The graph shows the effect of different sucrose concentrations on the length of the potato cylinders. When the sucrose solution was less than 0.3 mol dm -3, water molecules moved from a region of …1… negative water potential to a region of …2… negative water potential. Hence, water molecules moved from the ...3… into the …4…. If the initial length of the potato cylinder in 0.1 mol dm -3 sucrose solution is 5.0 cm, the final length will be …5…cm. Which words correctly fill gaps 1, 2, 3, 4 and 5? 1 2 3 4 5 A less more sucrose solution potato cells 5.5 B less more sucrose solution potato cells 4.5 C more less potato cells sucrose solution 5.5 D more less sucrose solution potato cells 4.5 ratio of initial length to final length of potato cylinders 0.1 0.2 0.3 0.4 0.5 concentration of sucrose solution / mol dm-3 1.3 1.2 1.1 1.0 0.9 0.8

5 © Hwa Chong Institution 2018 9744 H2 Biology / JC2 Preliminary Examinations / Paper 1 4 Fatty acid chains of natural membrane phospholipids may be saturated or unsaturated. fatty acid chain A fatty acid chain B Which statements regarding fatty acid chains A and B are correct? 1 The presence of phospholipids with mainly fatty acid chain A in cell membranes have increased membrane viscosity. 2 Fatty acid chain B is unsaturated because it contains one double bond creating a kink in the fatty acid structure. 3 A membrane containing predominantly fatty acid chain B has a greater fluidity than one which predominantly contains fatty acid chain A. 4 The presence of phospholipids with fatty acid chain B eases the passage of small, non-polar molecules, such as oxygen through membranes. A 1, 2, 3 and 4 B 1, 3 and 4 only C 1 and 2 only D 2 and 4 only C C H H

6 © Hwa Chong Institution 2018 9744 H2 Biology / JC2 Preliminary Examinations / Paper 1 5 The diagram shows the ribbon model of the cell surface membrane receptor, HLA-DR1. HLA-DR1 consists of two polypeptides, where parts of the protein are labelled P, Q and R. Which statement regarding the cell surface membrane receptor HLA-DR1 is correct? A In the formation of structure P, each hydrogen bond is formed between the –NH of one amino acid and the C=O group of another amino acid. B Q is important for the folding of the polypeptide into a specific 3D conformation of its active site. C R-group hydrogen bonding is involved in the formation of structure R. D Structures P, Q and R play a role in the formation of the quaternary structure of HLA- DR1. R P Q

7 © Hwa Chong Institution 2018 9744 H2 Biology / JC2 Preliminary Examinations / Paper 1 6 The graph shows the effect of an enzyme on a reaction. Which row correctly identifies the labels? reaction with enzyme difference in activation energy energy released during reaction A X 1 2 + 3 B Y 1 + 2 3 C X 1 + 2 1 + 2 + 3 D Y 1 3 1 2 3 product substrate key X Y energy

8 © Hwa Chong Institution 2018 9744 H2 Biology / JC2 Preliminary Examinations / Paper 1 7 Once most stem cells differentiate, they lose their ability to turn into other types of cells. However, some fully differentiated cells can be stimulated to change back into stem cells in tissue culture. Such cells are called induced pluripotent stem cells (iPS cells). In experiments with mice, it was discovered that the introduction of four genes would cause certain fully differentiated cells to change to iPS cells. Genes were introduced into host mouse cells using artificially synthesised plasmids. There is evidence to suggest that the introduction of the four genes caused an increase in the production of telomerase reverse transcriptase (TERT) in the fully differentiated cells. Which statements are correct? 1 The iPS cells are useful for research because they have the ability to differentiate into cells of the extra-embryonic membranes. 2 Only a few genes were required to be added because these genes were likely able to influence the activity of many other genes by coding for transcription factors. 3 TERT, which plays a part in maintaining the length of the telomere at the end of a chromosome, is not normally switched on in differentiated cells. 4 This method of creating iPS cells has less ethical concerns than harvesting embryonic stem cells. A 1, 2 and 3 B 1, 2 and 4 C 1, 3 and 4 D 2, 3 and 4

9 © Hwa Chong Institution 2018 9744 H2 Biology / JC2 Preliminary Examinations / Paper 1 8 The diagram shows the replication bubble of part of a DNA molecule. Which statements regarding the replication of DNA are correct? 1 At replication fork 1, synthesis of the complementary strand of DNA strand 1 is continuous. 2 At replication fork 2, DNA strand 1 requires multiple primers for the replication process. 3 Four DNA molecules are newly formed upon the completion of replication. A 1, 2 and 3 B 2 and 3 C 1 and 2 D 1 only DNA strand 1 DNA strand 2 origin of replication replication fork 2 replication fork 1 5’ 3’

10 © Hwa Chong Institution 2018 9744 H2 Biology / JC2 Preliminary Examinations / Paper 1 9 The diagram shows the transcription of a gene in a eukaryotic cell. Which statements are correct? 1 X is not transcribed except for the transcription start site. 2 RNA polymerase and transcription factors bind to Y to initiate transcripti