Dunman 2026 6093 Paper 1 and 2 MS v4

Paper 1 1 2 3 4 5 6 7 8 9 10 B D A B B D B C C A 11 12 13 14 15 16 17 18 19 20 B D B D C A D C C B 21 22 23 24 25 26 27 28 29 30 B D B D C B A B A B 31 32 33 34 35 36 37 38 39 40 D D B B B D D C C A Paper 2 1a • large / high, surface area to volume ratio / small / low, volume to surface area ratio • (SA:V ratio) 5.95:1 Accept anything between 5:1 and 7:1 • no cell is far from surface / short (diffusion) distance with reference to diffusion of, oxygen / carbon dioxide / gases Poorly done – only one student made the calculation correctly for SA:V ratio. Should take note of calculations that need to be done when question asks to refer to the diagram. In addition, many students only mentioned either high surface area to volume ratio or the short diffusion distance. Both are true for a long and thin organism and are separate points. bi • Homeostasis is the maintenance of a constant internal environment. Poorly done. Students should be clear this is a definition to know by heart. bii Any 3: • Freshwater has a higher water potential than the flatworm's body fluids, so water constantly enters the flatworm via osmosis. • By actively pumping ions into the tubules, it increases water potential in body cells which • Prevents cells from bursting/ rupturing. A challenging question, but those that understood the question scored very well. At the very least, students should take note that the salts are excreted which means body cells will have a higher water potential. This would be a clue to answering the question. 2ai • Mitochondrion

• Mitochondrion releases energy through aerobic respiration for the phagocyte to engulf pathogens / carry out phagocytosis. Some students still spelled it as mitochondrian, a grave error. Many did not refer to the white blood cell in question and merely stated the generic function of white blood cell. aii Difference 1: • Capillary walls are only one cell thick, • whereas artery walls are thick and muscular. • This provides a short diffusion distance for rapid exchange of gases and nutrients in capillaries, • whereas thick muscular artery walls withstand the high blood pressure coming from the heart. OR Difference 2: • Artery walls contain elastic fibers, • whereas capillary walls lack elastic tissue. • Elastic fibers allow arteries to stretch and recoil to maintain high blood pressure, • while the absence of these layers in capillaries allows the vessel to be thin enough for efficient substance exchange. Generally well done. Bi 0.1 to 0.42 seconds not well done. Most knew 0.1s was when ventricular systole started. However the duration was not correct after that. Students should refer to the textbook what the definition means. bii • Pressure in ventricle is higher than in aorta, semi-lunar valve in aorta open. • Blood flows from ventricle into the aorta. Well done. 3a • P: hepatic vein • Q: hepatic portal vein • R: hepatic artery Surprisingly, many were confused. Need to revise. b • When there is excess glucose, (increase is not accepted) • pancreas secrete insulin which is transported to the liver.

• Liver converts excess glucose to glycogen Well done. c • Catalase has a specific three -dimensional structural shape and active site. • The substrate, hydrogen peroxide, has a complementary shape that fits into the active site of catalase. • This allows them to bind together to form an enzyme-substrate complex for catalysis to occur, whereas other metabolic substances do not have a complementary shape and cannot bind. Well done. Many wrote 3D shape, which is not specific enough. 4ai Any 2: Urea/ creatinine / uric acid/ water / mineral salts Urea was a common answer. Many were not able to state that excess mineral salts and excess water has to be removed as well. aii Accept any 2 features with correct explanation (1m for feature, 1m for explanation) • Feature 1: Long, narrow, or highly coiled dialysis tubing Explanation: Provides a large surface area to volume ratio for faster diffusion of wastes • Feature 2: use of a partially permeable membrane. Explanation: allows small waste molecules (like urea) to pass through while preventing large blood cells/proteins from leaving. (must give example) • Feature 3: Counter-current flow mechanism / Blood and dialysis fluid flow in opposite directions. Also accept continuous replacement of dialysis fluid. Explanation: Maintains a steep concentration gradient for waste substances along the entire length of the tubing, preventing equilibrium from being reached and maximizing diffusion. Max 2 marks for features, max 2 marks for explanation. Well done. b Any 4 marks: • Increase in body temperature above normal stimulates the thermoreceptors and hypothalamus. • Arterioles in the skin dilate (vasodilate), allows more blood to flow through the blood capillaries near the skin surface, increasing heat loss through radiation, conduction, and convection. (must have the idea that more blood flow is to the skin)

• Sweat glands become more active and secrete more sweat onto the skin surface. As the water in the sweat evaporates , it absorbs latent heat of vaporisation from the body, significantly cooling the skin • The body may also decrease its metabolic rate to reduce the amount of heat released by internal chemical reactions. Body temperature decreases back to normal. Those who did study got most of the points, although most missed the first point about where the thermoreceptors are. 5a Any 1: • Bacterial DNA is not enclosed in a nucleus / lies free in the cytoplasm (whereas human DNA is inside a nucleus). OR Bacterial DNA is circular (whereas human DNA is linear). Done well. b Any 3: • The bacteria possess foreign proteins/structures on their surface called antigens. • White blood cells recognize/bind to these foreign antigens as non-self. • This stimulates the specific white blood cells to multiply and produce/secrete antibodies. • The structural shape of these antibodies is complementary to the specific antigens, allowing them to bind to and destroy the bacteria. Not done well. Most do not know what antigens are. Should be clear that white blood cells recognize antigens, and then not just produce the antibodies, but the white blood cells themselves multiply. ci • Enzyme: Restriction enzyme • Function: cuts DNA strands at specific nucleotide sequences (restriction sites) to create complementary sticky ends on both the target gene and the plasmid vector, allowing them to join together. Most did not get the second point, many for not spelling complementary correctly. cii • DNA ligase ciii • Transformation (Step Y): The recombinant plasmid is mixed with a bacterium such as E. coli • Temporary heat/electric shock is applied. This opens pores in the bacterium for the plasmid to enter • Bacteria are grown in a fermenter for mass production • Insulin protein is extracted and purified.

Many missed the point that the plasmid needs to be mixed with the bacterium. Also that the bacteria needs to multiply in a fermenter. 6a 1m each for correct variation continuous variation discontinuous Height weight Blood group Well done. b Couple 3 • For Aisha and Divya to have blood group O, they must inherit one recessive IO allele from each parent. Therefore, both biological parents must possess at least one IO allele. • For Brenda to have blood group A IA IO and Chloe to have blood group B IB IO, the IA allele must come from one parent and the IB allele from the other. • Consequently, the parents must be heterozygous, with the genotypes IA IO (Group A) and IB IO (Group B), which allows them to pass on the IA, IB, or IO alleles to their offspring. The explanation is the focus of the answer, due to the word explain. Students should take note