O-Level Pure Biology Paper 1 practice set

O-Level Pure Biology Paper 1 practice set. SET 1 1. Which organelle is the site of aerobic respiration in a cell? A. Ribosome B. Mitochondrion C. Golgi body D. Nucleus 2. Which structure is found in plant cells but NOT in animal cells? A. Cell membrane B. Mitochondria C. Cell wall D. Nucleus 3. Diffusion is best described as the movement of particles: A. From low to high concentration, requiring energy B. From high to low concentration, not requiring energy C. Of water only, across a partially permeable membrane D. Against a concentration gradient using a carrier protein 4. Osmosis is defined as the movement of: A. Solute molecules across a partially permeable membrane B. Water molecules from a region of lower to higher water potential C. Water molecules from a region of higher to lower water potential across a partially permeable membrane D. Any molecule using ATP energy 5. An enzyme's activity is most affected by changes in temperature and pH because these factors: A. Change the substrate's chemical formula B. Alter the shape of the enzyme's active site C. Increase the number of enzyme molecules D. Convert the enzyme into a substrate 6. Which test detects starch? A. Iodine B. Benedict's C. Biuret D. Ethanol emulsion 7. Which test detects protein? A. Iodine B. Benedict's C. Biuret D. Ethanol emulsion

8. Photosynthesis combines which raw materials to form glucose? A. Oxygen and water B. Carbon dioxide and water C. Oxygen and carbon dioxide D. Nitrogen and water 9. Which leaf structure allows gas exchange? A. Cuticle B. Stomata C. Xylem D. Palisade mesophyll 10. Which vessel transports manufactured food from leaves to other plant parts? A. Xylem B. Phloem C. Cambium D. Cortex 11. Which enzyme in saliva begins starch digestion? A. Pepsin B. Amylase C. Lipase D. Trypsin 12. Where is bile released into? A. Stomach B. Duodenum C. Oesophagus D. Large intestine 13. Villi increase absorption efficiency mainly by: A. Producing more enzymes B. Increasing surface area C. Slowing food movement D. Secreting HCl 14. Main function of red blood cells: A. Fight pathogens B. Clot blood C. Transport oxygen D. Transport digested food 15. Which heart chamber pumps oxygenated blood to the whole body? A. Right atrium B. Right ventricle C. Left atrium D. Left ventricle 16. Main advantage of a double circulatory system: A. Blood passes through the heart once per cycle B. Higher blood pressure and oxygen delivery to tissues

C. Fewer blood vessels needed D. Allows blood to bypass the lungs 17. Which vessel has the thinnest walls, allowing exchange with tissues? A. Artery B. Vein C. Capillary D. Aorta 18. During inhalation: A. Diaphragm relaxes and moves up; ribs move down B. Diaphragm contracts and moves down; ribs move up and out C. Both remain stationary D. Diaphragm contracts and moves up; ribs move in 19. Site of gas exchange in the lungs: A. Trachea B. Bronchus C. Alveolus D. Bronchiole 20. Main excretory product removed by kidneys: A. Carbon dioxide B. Urea C. Bile D. Glucose 21. Which part of the nephron performs ultrafiltration? A. Loop of Henle B. Glomerulus and Bowman's capsule C. Collecting duct D. Distal convoluted tubule 22. Which hormone lowers blood glucose? A. Glucagon B. Insulin C. Adrenaline D. Thyroxine 23. Which part of a neuron receives impulses? A. Axon B. Dendrite C. Myelin sheath D. Synapse 24. Small gap between neurons where impulses cross chemically: A. Axon B. Synapse C. Node of Ranvier D. Effector 25. Which eye structure controls light entering the eye? A. Cornea

B. Iris C. Retina D. Lens 26. Homeostasis refers to: A. Growth of an organism over time B. Maintenance of a constant internal environment C. Gas exchange in the lungs D. The process of reproduction 27. Which is a mitosis-related process? A. Formation of gametes with half the chromosome number B. Growth and repair of body tissues C. Genetic variation through crossing over D. Random segregation of homologous chromosomes 28. Meiosis results in: A. Two identical diploid cells B. Four genetically different haploid cells C. Four identical diploid cells D. Two genetically different diploid cells 29. Cross Tt × Tt gives what phenotype ratio (complete dominance)? A. 1:1 B. 1:2:1 C. 3:1 D. 9:3:3:1 30. A person with genotype XHXh is a carrier for haemophilia. This tells us the allele is: A. On an autosome B. Dominant C. Recessive and sex-linked D. Cannot be passed on 31. A mutation is best described as: A. The normal process of cell division B. A change in the DNA base sequence C. Pairing of homologous chromosomes D. Transfer of pollen between flowers 32. In genetic engineering, the role of a plasmid is: A. To act as a vector carrying the desired gene into a host cell B. To cut DNA at specific sequences C. To join DNA fragments permanently D. To translate mRNA into protein 33. Protein synthesis (translation) takes place at the: A. Nucleus B. Ribosome C. Mitochondrion D. Golgi body

34. Main role of decomposers: A. Photosynthesise B. Consume producers directly C. Break down dead matter and recycle nutrients D. Store energy as biomass 35. In a food chain, the arrow represents: A. Direction of predation B. Flow of energy C. Direction of nutrient absorption D. Reproductive relationship 36. Why is only ~10% of energy transferred between trophic levels? A. Organisms only eat 10% of available food B. Energy lost as heat via respiration; not all biomass eaten/digested C. Decomposers absorb 90% D. Producers store 90% underground 37. A species is defined as: A. Organisms living in the same habitat B. Organisms that can interbreed to produce fertile offspring C. Organisms sharing a common ancestor D. Organisms with the same diet 38. Natural selection acts on variation primarily by: A. Creating mutations directly in response to need B. Favouring individuals with advantageous traits, who survive and reproduce more C. Ensuring equal reproduction for all D. Eliminating all genetic variation 39. Germination is: A. Fusion of male and female gametes B. Growth of a seed into a seedling under suitable conditions C.