Biology 9700/06 May June 2004 | Cambridge AS Level Past Papers With Mark Scheme

1. Pepsin activity in the stomach: secretion as inactive pepsinogen, activation by hydrochloric acid, and protein hydrolysis into smaller peptides.

2. Bone density and fracture risk: gender-specific age trends in osteoporosis, femur fractures linked to density reduction, and osteoporotic risk increases with age.

3. Urea cycle in the liver: conversion of excess amino acids into urea via transamination and ammonia production; advantages of direct ammonia excretion in aquatic organisms.

4. Eye responses: pupil constriction to increased light via parasympathetic activation and lens curvature changes for focusing on near objects controlled by ciliary muscle contraction.

5. Virus structure and multiplication: capsid, nucleic acid, and host cell lysis; HIV transmission trends and immune suppression via T-cell destruction.

6. Fusarium mycoprotein production: air-lift fermenter function, nutrient requirements, and post-fermentation processing for human consumption.

7. Genetic engineering for insulin production: recombinant DNA technology reducing allergic responses and ethical concerns compared to pig-derived insulin.

8. Plantlet cloning in tissue culture: auxin and cytokinin effects on callus growth; sterilization techniques minimizing fungal and bacterial contamination in explants.

9. Genetic principles: F2 generation phenotypic ratios in dihybrid crosses and application of gene therapy for recessive diseases like hemophilia.