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Topic 4.1: Cell biology

Subtopic 4.1.1: Cell structure

4.1.1.1 - Eukaryotes, Prokaryotes and Cell ScaleCells are the smallest living units, but they are not all organised in the same way. In this lesson, the main difference is where the genetic material is found: inside a nucleus in eukaryotic cells, but not inside a nucleus in prokaryotic bacterial cells. You will also practise the scale language...
4.1.1.2a - Animal and Plant Cell StructuresCells are easier to understand when you treat each labelled part as a structure with a job. In this lesson, the key skill is not just naming the parts of animal and plant cells, but explaining how each sub-cellular structure is related to its function. Bacterial plasmids are included only where t...
4.1.1.2b - Microscopy of Plant and Animal CellsIn this required practical, you use a light microscope to observe plant and animal cells, then record what you see as a clear labelled scientific drawing. AQA can assess the method, the apparatus, safe focusing, drawing conventions, magnification scale, and estimates of relative size or area. The...
4.1.1.3 - Cell SpecialisationDifferent cells can have different shapes and subcellular structures because they do different jobs. In this lesson, the key skill is to explain a structure-function link: name a feature, state what it does, then connect it to the cell's role in a tissue, organ, organ system or whole organism.
4.1.1.4 - Cell DifferentiationOne cell is not enough to build a complex organism. As an organism develops, cells change so that different cells can do different jobs. This change is called cell differentiation, and it is how ordinary developing cells become specialised cells.
4.1.1.5 - Microscopy, Magnification and ResolutionMicroscopes let biologists study cells and the structures inside them. As microscope technology improved, biologists could make images bigger and, more importantly, see finer detail. This lesson focuses on how light and electron microscopes differ, and how to handle magnification calculations wit...
4.1.1.6a - Culturing Microorganisms and Bacterial GrowthMicroorganisms are tiny living organisms. In this biology-only section, the focus is bacteria: how they multiply, how they can be grown in nutrient media, and how to do the calculations that come from bacterial growth on agar plates. The key pattern is doubling, so a small starting population can...
4.1.1.6b - Aseptic Technique and Zones of InhibitionIn this Biology-only required practical, you prepare an uncontaminated bacterial culture and test how well antiseptics or antibiotics inhibit bacterial growth. The result is judged from clear areas on an agar plate called zones of inhibition. The practical is really about two linked skills: keepi...

Subtopic 4.1.2: Cell division

4.1.2.1 - Chromosomes, DNA and GenesChromosomes are one of the key links between cell biology and inheritance, but this lesson keeps to the first GCSE idea: where chromosomes are, what they are made of, what they carry, and how they are normally arranged in body cells. The important exam skill is to describe the relationship betwee...
4.1.2.2 - Mitosis and the Cell CycleMulticellular organisms become larger because their cells divide as well as grow. In this topic, the important idea is that the cell cycle copies the genetic material and then divides it so two identical cells are made. You need the overall order of events, not the named phases inside mitosis.
4.1.2.3 - Stem CellsStem cells matter because they are not yet specialised. They can make more cells of the same type, and some of their cells can become specialised by differentiation. This lesson keeps the exam boundary clear: you need the functions, uses and evaluation points, not the detailed laboratory techniques.

Subtopic 4.1.3: Transport in cells

4.1.3.1a - Diffusion and Factors Affecting Its RateCells constantly exchange substances with their surroundings. Diffusion is one way particles move into and out of cells across cell membranes, and it matters because cells need useful substances while removing waste. This lesson focuses on what diffusion means, examples named in the specification...
4.1.3.1b - Surface Area to Volume Ratio and Exchange SurfacesEvery cell needs substances to move in and out across a surface. As organisms get larger, their volume increases faster than their outside surface area, so diffusion across the body surface alone becomes too slow. This lesson shows how to calculate surface area to volume ratio, then uses that ide...
4.1.3.2a - Osmosis and Water MovementWater can move into and out of cells through the cell membrane. The AQA word for this movement is osmosis, and the definition is exact: it is about water, a partially permeable membrane, and movement from a dilute solution to a concentrated solution. In this lesson you will learn how to follow th...
4.1.3.2b - Required Practical - Osmosis in Plant TissueIn this required practical, you investigate how the concentration of a salt or sugar solution affects the mass of plant tissue. The biology is osmosis, but the exam marks often come from practical detail: variables, accurate mass measurements, percentage change, graph interpretation and evaluatio...
4.1.3.3 - Active TransportCells sometimes need useful substances even when those substances are already more concentrated inside the cell or in the blood. Diffusion cannot do that job, because diffusion only gives a net movement down a concentration gradient. Active transport is the process that moves substances against a...

Topic 4.2: Organisation

Subtopic 4.2.2: Animal tissues, organs and organ systems

4.2.2.1a - Digestive System, Enzymes and DigestionThe digestive system is an organ system: several organs work together to digest food and absorb the useful small molecules into the bloodstream. Digestion matters because large food molecules are often insoluble and too large to be absorbed. Enzymes speed up the chemical breakdown of these food m...
4.2.2.1b - Required Practical - Food TestsFood tests use chemical reagents to identify molecules in food samples. In this required practical, the tested molecules are sugars, starch, lipids and protein, using Benedict's solution, iodine solution, Sudan III stain and Biuret reagent. The results are qualitative: they tell you whether a sub...
4.2.2.1c - Required Practical - Amylase and pHThis required practical investigates how pH affects the rate at which amylase digests starch. You use iodine reagent to test whether starch is still present, and you control temperature so that pH is the factor being tested. AQA can assess the method, variables, safety, observations, rate calcula...
4.2.2.2 - The Heart and Blood VesselsThe circulatory system moves substances around the body quickly, so cells can receive oxygen and glucose and remove carbon dioxide. In humans, the heart is the muscular organ that pumps blood through blood vessels. This lesson focuses on the AQA boundary: the double circulatory system, the named...
4.2.2.3 - BloodBlood is a tissue: it contains different components that work together to transport substances, defend the body and reduce blood loss after injury. The liquid part is plasma, and suspended in it are red blood cells, white blood cells and platelets. AQA expects you to know the function of each com...
4.2.2.4 - Coronary Heart Disease and TreatmentsCoronary heart disease is a non-communicable disease that affects the blood supply to the heart muscle itself. The key GCSE idea is simple but important: narrowed coronary arteries carry less blood, so the heart muscle receives less oxygen. Treatments can improve blood flow, reduce further fatty...
4.2.2.5 - Health Issues and Disease InteractionsHealth is not just the absence of disease. In this lesson, health means physical and mental well-being, and diseases are one major cause of ill health. You will also learn how different types of disease can interact, and how AQA expects you to handle disease incidence data.
4.2.2.6 - Lifestyle Risk Factors and Non-Communicable DiseaseNon-communicable diseases are not passed from person to person, but their incidence can still change between groups of people. In this lesson, you will link lifestyle risk factors to some non-communicable diseases, then practise the data language AQA expects: sampling, correlation, graphs and num...
4.2.2.7 - CancerCancer starts when changes in cells disrupt the normal control of growth and division. The key idea is not to memorise many named cancers, but to describe how abnormal cells can form tumours, why benign and malignant tumours are different, and why risk factors affect the chance of developing cancer.

Subtopic 4.2.3: Plant tissues, organs and systems

4.2.3.1 - Plant TissuesPlants are organised: cells with similar jobs form tissues, and different tissues work together in organs. In this lesson, the main organ is the leaf. The exam focus is not just naming leaf tissues, but explaining how each tissue's structure helps it carry out its function.
4.2.3.2a - Plant Transport Organs And TranspirationRoots, stems and leaves work together as a plant organ system for transport. This lesson follows the route of water and mineral ions from the soil to the leaves, then explains how water is lost by transpiration and how the plant controls that loss. The key exam habit is to link each structure to...
4.2.3.2b - Translocation and Plant Transport DataPlants need a transport system because roots, stems and leaves do different jobs in different places. This lesson focuses on phloem and translocation, then on the data skills used when plant transport is investigated. Keep the two transport tissues separate: xylem is the water and mineral ion rou...

Topic 4.3: Infection and response

Subtopic 4.3.1: Communicable diseases

Subtopic 4.3.2: Monoclonal antibodies

Subtopic 4.3.3: Plant disease

Topic 4.4: Bioenergetics

Subtopic 4.4.1: Photosynthesis

Subtopic 4.4.2: Respiration

Topic 4.5: Homeostasis and response

Subtopic 4.5.1: Homeostasis

Subtopic 4.5.2: The human nervous system

Subtopic 4.5.3: Hormonal coordination in humans

Subtopic 4.5.4: Plant hormones

Topic 4.6: Inheritance, variation and evolution

Subtopic 4.6.1: Reproduction

Subtopic 4.6.2: Variation and evolution

Subtopic 4.6.3: The development of understanding of genetics and evolution

Subtopic 4.6.4: Classification of living organisms

Topic 4.7: Ecology

Subtopic 4.7.1: Adaptations, interdependence and competition

Subtopic 4.7.2: Organisation of an ecosystem

Subtopic 4.7.3: Biodiversity and the effect of human interaction on ecosystems

Subtopic 4.7.4: Trophic levels in an ecosystem

Subtopic 4.7.5: Food production

Topic 4.8: Key ideas

Synoptic connections across biology