NYGH 2021-S3EOY-IP Bio P1 and P2 Ans

Paper 1 1 B Hepatic refers to the liver. Mesophyll refers to the leaf. 2 B Proteins cannot be sent for modification. Proteins (enzymes present in lysosome), membrane proteins present in cell membrane may be affected. 3 D Prokaryotes do not have intermembranous systems. Chloroplast is a double membrane bound organelle. 4 B Each nucleotide contains a sugar, a base and a phosphate group. Thus, a gene that contains 900 phosphate groups also contains 900 bases. 5 C Amino acids do not bind to mRNA. A particular number and types of amino acids are chemically joined together by peptide bonds via condensation reaction, in a particular sequence next to each other to form polypeptide. Polypeptide will then fold to form protein. Protein is a structure with specific 3-dimensional conformation, hence able to have a specific function. 6 C There should not be uracil base present in DNA. There should not be thymine present in RNA. Follow the complementary base pairing rule: A-T (in DNA-DNA) or A- U (in DNA-RNA), and G-C (in DNA-DNA or DNA-RNA). 7 C 1. Mutations are spontaneous and random. They give rise to new alleles. 2. Not true. 4. May not be true. 8 D Man with blood type AB is not able to pass down a IO allele. Blood type O is not possible. 9 C The mother’s genotype is X HXh as the couple has a son who is haemophiliac. This son has inherited the X h from her since the father will pass down the Y chromosome. 10 B Fertilisation le ads to doubling of DNA content. DNA replication in interphase again doubles the amount of DNA. 11 B Alignment of the chromosomes at the equator of the cell ensures that the sister chromatids separate to the opposite poles. The formation of the nuclear membrane around the daughter chromosomes ensure that each cell will receive a specific chromosome. 12 A / B Events in cytokinesis. 13 A Glucose can be synthesized into cellulose required for cell wall structure in plants only. In animals only, excess glucose is synthesized into glycogen for storage only in liver and muscles. Plants store excess glucose in the form of starch granules/grains within chloroplasts. In animals only, glycogen can be broken down back into glucose for use in cellular processes like respiration to release energy. 14 C Lactose is a disaccharide made of glucose and galactose molecules. The chemical formula for both glucose and galactose is C6H12O6. During condensation reaction, one water molecule i.e. H2O is removed when both molecules are joined together via glycosidic bond. Hence, [C6H12O6 (times) 2] (minus) H2O (equals) C12H22O11 15 C The temperature differences are 67 oC (food 1), 86 oC (food 2), 11 oC (food 3) and 66 oC (food 4). Higher lipid content result in higher energy during burning. Lipid molecules are good energy storage molecules.

16 D Phospholipid is a type of lipid molecule made up of 1 glycerol molecule chemically combined (via ester linkages by condensation reactions) with 2 fatty acid chains and 1 inorganic phosphate group. Phospholipid molecule could be modified with replacement of the inorganic phosphate group with a short carbohydrate chain (or called: sugar residues) that is chemically combined to the glycerol molecule. 17 C Boiling will destroy cell membranes’ structure. Hence, osmosis that requires selectively permeable membrane will not be able to occur. Free water molecules will be bounded to solutes (i.e. salt), hence preventing osmosis since there will not be any difference in water potentials. Solutes will still be able to move by simple diffusion (with no requirement of membrane presence), from higher concentration of salts in the solution towards lower concentration of salts in the cell sap of potato. 18 D Cell surface membrane is considered hydrophobic due to the presence of fatty acid chains. Fat soluble molecules can move across directly via simple diffusion. For water soluble molecules, transmembrane protein will be required for a through passage of these molecules. 19 A Lock refers to the enzyme with the active site of specific 3-dimensional conformation. Key refers to the substrate (with specific conformation, size and charge) complementary to the active site of the enzyme involved. Usually enzymes have name ending with ‘ -ase’, but with some ending with ‘-in’. 20 B At temperature below optimum, enzymes are inactive due to low kinetic energy. Higher temperature i.e. higher heat energy will result in higher kinetic energy of molecules. Enzyme at 60°C will have higher kinetic energy as compared to those at 40°C. At temperature above optimum, enzymes are denatured i.e. loss of active site with specific 3-dimensional conformation. This is due to the excess heat energy disrupting weak chemical bonds within the protein structure of enzymes. Hence, enzyme -substrate complex will not be formed. During enzyme -substrate complex formation, temporary chemical bonds e.g. hydrogen bonds are formed between enzyme (at the active site) and substrate. 21 A Comparing 1 and 2, the results prove that zinc ions help to increase rate by 10 times. And water as a substituent, decreased the rate by 10 times. Comparing 1 and 3, the results prove that retinoic acid helps to increase rate by 25 times. Hence, acidic pH denaturation to the enzyme will not be possible. 22 C Fact. Ileum as part of small intestine. 23 B The constriction of oesophagus lumen at region N leads to deduction that food bolus is moving to the left. This is a result of contraction of circular muscles, and the relaxation of longitudinal muscles at region N. 24 D Organ 1 – mouth contains salivary amylase which catalyses the hydrolysis of glycosidic bonds within starch molecules to form maltose. Organ 2 – stomach churns the food to break up food into smaller pieces with higher surface area to volume ratio.

Organ 3 – mouth performs chewing of food to break up food into smaller pieces with higher surface area to volume ratio. Organ 4 – stomach contains pepsin which catalyses the hydrolysis of bonds within proteins to form polypeptides. 25 A Stomach (A) is involved in protein digestion and food is temporarily held in the stomach for 3-4 h before release into the duodenum. Pancreas (B) release pancreatic juice containing various digestive enzymes into the duodenum but is not involved in egestion. Duodenum (C) is involved in carbohydrate digestion but not assimilation. Gall bladder is stores bile for fat emulsification but is not involved in absorption. 26 B At lower carbon dioxide concentration, the increase in carbon dioxide concentration increases rate of photosynthesis. But at higher carbon dioxide concentration, the experiment at higher temperature results in a higher rate of photosynthesis. 27 A 1 has no chlorophyll and 2 has. 28 A Fact. 29 A A is the phloem which is involved in translocation. 30 D Region 1 on the leaf is where the xylem is found. D is the xylem

Paper 2 Mark scheme abbreviations (aligned with Cambridge) / alternative answers for the same point () contents of brackets are not required but should be implied + statements on both sides of the + are needed for that mark R reject A accept (for answers correctly cued by the question, or by extra guidance) AVP alternative valid point (where a greater than usual variety of responses is expected) AW alternative wording (where responses vary more than usual) ECF error carried forward Ig ignore (for incorrect but irrelevant responses) Max indicates the maximum number of marks that can be given ORA or reverse argument underline actual word given must be used by candidate (grammatical variants accepted)

Q 1 Answer Guidance (a) a b (Correct measurement with units) Length of XY in Figure = 3.7 cm Magnification = Length of XY in Figure/ Actual length of XY Actual length of XY = 3.7 cm/ 47 500 = 0.00007789 cm = 0.78 µm answer with unit