DHS 2023 Y5 H2 Promo Answer Scheme (Paper 1 and 2)

1 DUNMAN HIGH SCHOOL Promotional Examination Year 5 H2 Biology Promo Exam 2023 Mark Scheme Paper 1: Multiple Choice Question 1 A 6 B 11 A 2 D 7 D 12 A 3 D 8 B 13 C 4 C 9 A 14 D 5 B 10 B 15 D Q Explanation 1 Region P refers to the nucleoid region and region Q the nucleolus. Statement 1: True Statement 2: RNA synthesise in P and rRNA in Q. Statement 3: ATP synthesis occurs in mitochondria and chloroplasts. Statement 4: Circular DNA found in bacteria, mitochondria, and chloroplasts. 2 The larger the organelle, the lower the centrifugal speed required for the organelle to sediment. Diagram shows the size of the organelles. Liquid 1 contain all organelles except largest organelle – nucleus Liquid 2 –nucleus and mitochondria removed Liquid 3 –nucleus, mitochondria, and endoplasmic reticulum removed 3 Statement 1 is false: Triglycerides have hydrophobic regions too. Statement 2 is false: The fatty acids in a triglycerides may not be always saturated. Statement 3 true. Statement 4 is false: Phospholipids is polar whereas triglycerides is non-polar. 4 Statement 1: glucose monomers arranged in the same orientation will give a helical structure thus structure is compact and thus suitable as energy store. Statement 2: Fact. But does not account for starch being suitable as an energy storage molecule. Statement 3: amylopectin is more branched than amylose. So more compact and thus a suitable as energy store. Statement 4: will remain insoluble at room temperature so suitable as energy store. Statement 5: Fact. But does not account for starch being suitable as an energy storage molecule.

2 5 Graph is an endothermic reaction activation energy graph. Statement 1: X shows potential energy of reactants. Statement 2: Y shows activation energy. Statement 3: you need to see another graph showing lowering of activation energy to be sure that enzyme is added to the reaction. Statement 4: This is factual statement but cannot be concluded from the graph since there is no information about proximity effect. Statement 5: can see from graph. . 6 X has ribose sugar and Y has deoxyribose sugar. Statement 1: True, X forms 2 hydrogen bonds with T. Statement 2: X has ribose sugar, not deoxyribose sugar. Statement 3: True, Y forms 2 hydrogen bonds with U. Statement 4: No uracil used in replication. 7 Types and amount of DNA in: Picture 1: all double stranded 15N15N Picture 2: all double stranded 15N14N, Picture 3: 50% double stranded 15N14N and 50% double stranded 14N14N. So, it is 25% of DNA is 15N and 75% of DNA is 14N. 8 Statement 1: Fact but not answering question. Statement 2: True, need to have the genome sequence to synthesize primers. Statement 3: Factors e.g. length of genome, type of DNA polymerase used, may determined the temperature used for the three stages. Statement 4: Only sterile technique can ensure that there is no contamination. 9 All bands in the s