Biology 9700/04 Oct Nov 2005 | Cambridge AS Level Past Papers With Mark Scheme

1. Krebs cycle processes: location in mitochondrial matrix, stages of decarboxylation and dehydrogenation, NAD regeneration, and ATP production via substrate-level phosphorylation.

2. Maize grain genetics: dihybrid cross ratios for purple/yellow and smooth/shrunken phenotypes, chi-squared test application, and conclusions on expected vs. observed ratios.

3. Respiratory quotient (RQ): calculation for substrate metabolism, identification of fats as substrates with lower RQ values, and comparative energy yield of carbohydrates vs. fats.

4. Darwin's finches: environmental selection pressures during drought affecting beak size, stabilizing selection under normal conditions, and mechanisms of speciation on Galapagos Islands.

5. Genetic engineering of insulin: plasmid DNA cleavage with restriction enzymes, ligation of insulin gene using ligase, and advantages of recombinant insulin for diabetic treatments.

6. Photosynthesis in dicot leaves: structural adaptations like chloroplast arrangement and stomatal control; impact of light intensity and CO\\(_2\\) concentration on photosynthetic rate.

7. Nitrogenous waste formation: protein catabolism producing ammonia, conversion to urea, and excretion via kidneys; filtration and selective reabsorption in nephron processes.