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ā ļø A Gentle Reminder: Check the Full Specification
Before we dive into the crystal ball, please remember: we have not seen the exams. While we spend hours analysing trends to write these papers, examiners can be unpredictable. These predictions are designed to guide your revision, not replace it. Always review the full AQA A-Level Biology Specification to ensure you are covered for everything!
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𧬠Revision Guide: Predicted Topics for Paper 2 & Paper 3
Based on our analysis for 2026, here are the topics we expect to see on Paper 2 (Topics 5ā8) and the Synoptic Paper 3. Use this list to focus your final revision sessions!
āļø Photosynthesis: Light-Dependent Reactions
Location: Thylakoid membranes of chloroplasts.
Process: Photoionisation of chlorophyll excites electrons. Photolysis splits water.
Outcomes: Production of ATP (chemiosmosis) and Reduced NADP for the Light-Independent Reaction.
Practical:Ā Redox reactions using DCPIP (blue to colourless when reduced) to measure dehydrogenase activity.
šĀ Respiration (Anaerobic Focus)
Glycolysis: Glucose ā Pyruvate (Net 2 ATP, 2 Reduced NAD). Occurs in cytoplasm.
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Anaerobic Paths:
Plants/Yeast: Pyruvate ā Ethanol + CO2.
Animals: Pyruvate ā Lactate.
Key Function: Regenerates oxidised NAD so glycolysis can continue.
ā” Productivity & Energy Transfers
GPP vs NPP: Gross Primary Production (total energy) vs Net Primary Production (energy available for next trophic level).
Energy Loss: Lost via heat (respiration), excretion, or inedible parts.
Efficiency: Percentage efficiency = (Energy available after transfer / Energy available before) x 100.
ā»ļø Nutrient Cycles (Phosphorus Focus)
No Gas Phase: Unlike Nitrogen, Phosphorus is sedimentary.
Key Steps: Weathering of rocks releases phosphate ions PO43-. Absorption by plants (often aided by Mycorrhizae - fungal associations increasing surface area). Eating/digestion by animals. Decomposition (saprobionts) returns ions to soil.
šļø Visual Receptors
Rods: High sensitivity (work in dim light) due to spatial summation (many rods : 1 bipolar neurone). Low visual acuity. Pigment: Rhodopsin.
Cones: Low sensitivity (need bright light). High visual acuity (1 cone : 1 bipolar neurone). Pigment: Iodopsin (3 types for absorbing red, green and blue light).
ā¤ļø Control of Heart Rate
Myogenic: Heart beats on its own, but rate is controlled by the medulla oblongata.
Chemoreceptors: Detect pH/CO2 changes (e.g., exercise increases CO2, lowers pH).
Baroreceptors: Detect blood pressure changes in aorta/carotid arteries.
Effect: Impulses sent via sympathetic (increases HR) or parasympathetic (decreases HR) nerves to the SAN.
šŖ Muscle Contraction & Neuromuscular Junction
Sliding Filament Theory: Calcium ions bind to troponin, moving tropomyosin to expose binding sites on actin. Myosin heads bind (cross-bridge), power stroke (ADP released), ATP binds to detach myosin head.
Neuromuscular Junction: Action potential arrives ā Calcium influx ā Acetylcholine released ā Binds to receptors on sarcolemma āDepolarisation.
š¦Ā Actions of Adrenaline (Second Messenger Model)
Mechanism: Adrenaline (first messenger) binds to receptor on cell surface.
Inside Cell: Activates enzyme Adenylate Cyclase, which converts ATP to cAMP (second messenger).
Response: cAMP activates Protein Kinase, leading to glycogenolysis in liver cells (Glycogen ā Glucose).
š§Ā Kidney Structure & Function
Ultrafiltration: High hydrostatic pressure in glomerulus forces small molecules into Bowmanās capsule.
PCT: Selective reabsorption of all amino acids, glucose (co-transport), some ions and water.
Loop of Henle: Maintains sodium ion gradient for water reabsorption.
DCT/Collecting Duct: Permeability controlled by ADH (Anti-Diuretic Hormone) via aquaporins.
š§Ŗ Urine Calibration Curve (Practical 11)
Concept: Using serial dilutions to create known concentrations.
Analysis: Creating a calibration curve to identify the concentration of an unknown sample (e.g., glucose or protein concentration in urine) by comparing absorbance.
š±Ā Plant Responses & Hormones
IAA (Indoleacetic Acid): Controls tropisms.
Phototropism: IAA diffuses to shaded side āCell elongation (shoots) ā Bending towards light.
Gravitropism: IAA accumulates on lower side. Inhibits elongation in roots (bend down), promotes in shoots (bend up).
š§© Inheritance (Epistasis Focus)
Epistasis: When the allele of one gene affects or masks the expression of another gene.
Ratios: Watch out for modified dihybrid ratios like 9:3:4 (recessive epistasis) or 12:3:1 (dominant epistasis).
š¦ Speciation
Allopatric: Geographical isolation prevents gene flow. Different selection pressures ā Change in allele frequency.
Sympatric: Reproductively isolated in the same area (e.g., temporal or behavioural isolation) ā Change in allele frequency.
š Conservation
Importance: Maintaining biodiversity, ethical reasons, economic resources.
Balance: Managing conflict between human needs and conservation.
š§¬Ā Mutations
Types: Substitution, Deletion, Addition, Inversion, Duplication, Translocation.
Frame Shift: Caused by addition/deletion, changes all subsequent triplets.
Increase Risk: High energy radiation, mutagenic chemicals.
š§ŖĀ Stem Cells
Totipotent: Can divide into any cell type (early embryo).
Pluripotent: Almost any cell type (embryonic).
Multipotent: Limited types (adult bone marrow).
Unipotent: One type (e.g., cardiomyocytes).
iPS Cells: Induced Pluripotent Stem cells; adult cells reprogrammed using transcription factors.
š„Ā Cancer
Tumour Suppressor Genes: Usually slow division; mutation makes them inactive.
Proto-oncogenes: Stimulate division; mutation turns them into Oncogenes (permanently switched on).
Methylation: Hypermethylation of tumour suppressors can silence them.
š§Ā Controlling Gene Expression (siRNA Focus)
siRNA (Small Interfering RNA): Double-stranded RNA broken down into single strands.
Mechanism: complementary to target mRNA - binds to prevent ribosome binding or causes enzymes to destroy mRNA.
Result: Translation is prevented so no protein produced and gene is silenced.
āļø Genetic Modification
Recombinant DNA: Inserting DNA from one organism into another.
Steps: Isolation (Reverse Transcriptase, Restriction Endonucleases, Gene Machine) ā Insertion (Vector/Plasmid) ā Transformation (Host cell) ā Identification (Marker genes).
šŖ Gel Electrophoresis & Genetic Fingerprinting
Electrophoresis: Separates DNA fragments by size using voltage (DNA is negative, moves to positive). Smaller fragments move faster.
Fingerprinting: Analyses VNTRs (Variable Number Tandem Repeats). Unique to individuals (except identical twins).
𩺠Genetic Screening & Counselling
Screening: Testing DNA for mutated alleles.
Counselling: Advising patients on the risks/implications of genetic disorders based on family history and screening results.
š The Exam Structure
Knowing exactly what you are walking into is half the battle! Here is the breakdown for AQA A-Level Biology:
Paper 2 (7402/2)
Content: Topics 5ā8 (Energy transfers, Organisms' responses, Genetics, Populations, Evolution, Gene expression).
Marks: 91 marks.
Duration: 2 hours.
Format: Short and long answer questions + Comprehension Question (15 marks).
Paper 3 (7402/3) - The Synoptic Paper
Content: Topics 1ā8 (Everything!).
Marks: 78 marks.
Duration: 2 hours.
Format: Structured questions, critical analysis of practicals, and The Essay (25 marks).
Good luck, take care of yourself, and go show that exam paper what you are made of! You've got this! š
