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Biology A-Level Past Paper Questions (AS), Exams of Biology

A collection of past paper questions for biology a-level (as) exams. It provides a valuable resource for students preparing for their exams, offering insights into the types of questions they can expect and the key concepts they need to master. Questions on topics such as lipid identification, enzyme action, dna replication, calibration curves, haemoglobin function, tissue fluid accumulation, breathing mechanisms, asthma, leaf surface area, and countercurrent systems in fish. Each question is accompanied by a correct answer, providing students with a clear understanding of the expected responses.

Typology: Exams

2024/2025

Available from 12/22/2024

Expressguide
Expressguide 🇺🇸

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Biology A-Level Past Paper questions (AS)

Describe how to test for the presence of a lipid - correct answer Add ethanol, then add water, white emulsion shows lipid Describe the induced fit mode of enzyme action - correct answer Active site not complementary to substrate. Shape of active site changes as substrate binds stressing bonds. Why does DNA polymerase work in different directions in DNA replication - correct answer DNA has anttiparallel strands The nucleotides are alligned differently Enzymes have acttive sites with specific shape Only substrates with complementary shape caan bind with ative site of DNA polymerase Describe how to produce a calibration curve and used to obtain results (Benedict's test) - correct answer Make maltose solutions of know concentrations Measure colorimeter value of each soluton and plot calibration curve Find concentration of sample from calibration curve Describe the role of haemoglobin in supplying oxygen to the tissues of the body - correct answer Haemoglobin associates with oxygeen in areas of higher ppO Oxygen dissociates in areas of lower ppO

High blood pressure leads to an accumulation of tissue fluid, explain how

  • correct answer High blood pressure means high hydroststic pessure. This increases outward pressure from arterial end of capillary so more tissue fluid is formed. Explain the role of the diaphragm in breathing out - correct answer Diaphragm moves up Reduces volume in thorax Pressure in thorax higher than outside Describe and explain the mechanism that causes forced expiration - correct answer Contraction of internal intercostal muscles Relaxation of diaphragm muscles Causes decrease in volume of chest Air pushed down pressure gradient Explain how an asthma attack causes a drop in the mean FEV - correct answer Muscle walls of bronchi contract Walls of bronchi sectrete more mucus Diameter of airways reduced Flow of air reduced Describe a method to find the surface area of a leaf - correct answer Draw around the leaf on graph paper

Cut out and count the squares Multiply by 2 for upper and lower surface Describe and explain how the counter current system leads to efficient gas exchange across the gills of a fish - correct answer Water and blood flow in opposite directions Maintains concentration gradient Along whole length of gill Suggest and explain why the combined effects of endopeptidases and exopeptidase are more efficient than exopeptidase on their own - correct answer Exopeptidases remove amino acids at the end Increased surface area