Key term
AQA GCSE Combined Science Biology 8464
Bioenergetics
Cell Biology
Topic overviewEukaryotes and prokaryotesAnimal and plant cellsCell specialisation and differentiationMicroscopyChromosomes, mitosis and the cell cycleStem cells in embryos, adults and meristemsTherapeutic cloning, its risks, and cloning plantsDiffusion and the factors affecting its rateSurface area to volume ratio and exchange surfacesOsmosisActive transport
Ecology
Topic overviewLevels of organisation in an ecosystem, and what organisms needCompetition, interdependence and stable communitiesAbiotic factorsBiotic factorsAdaptationsProducers, food chains and sampling with quadrats and transectsPredators, prey and measuring population sizeHow materials are cycledWaste management and biodiversityLand use, deforestation and global warmingMaintaining biodiversity
Homeostasis and Response
Infection and Response
Inheritance, Variation and Evolution
Topic overviewSexual and asexual reproductionMeiosisDNA and the genomeGenetic terms, dominant and recessive allelesPunnett squares, probability and genetic crossesInherited disorders and sex determinationVariationEvolutionSelective breedingWhat genetic engineering is, and what it is used forGM crops, their risks, and the steps of the processEvidence for evolution, and extinctionFossilsResistant bacteriaClassification of living organisms
Organisation
Topic overviewLevels of organisation, and how enzymes workAmylase, proteases and lipasesBile, food tests and the effect of pH on amylaseThe heart, the lungs and double circulationThe pacemaker, the blood vessels and the bloodCoronary heart disease: a non-communicable diseaseHealth issuesRisk factors and causal mechanisms in diseaseSampling, correlation and interpreting risk dataCancerPlant tissues, and transpiration and its rateRoot hair cells, xylem, phloem and stomata
Cell Biology
Osmosis
- 3 things to know
- Biology Paper 1
Overview
Osmosis and partially permeable membranes, plant tissue in pure water and sugar solution, percentage change in mass and water uptake, the potato cylinder method and its variables, accuracy, precision, repeatability and reproducibility, systematic, zero and random errors, gradients and y = mx + c, and a hypothesis.
What you need to know
Answer each one before you reveal it.
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Key term
What is a partially permeable membrane?
Key term
Describe what happens to a piece of plant tissue placed in pure water.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define osmosis.
Model answer
The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
- 2
What is a partially permeable membrane?
Model answer
A membrane that lets water molecules pass through but not larger solute molecules.
- 3
Describe what happens to a piece of plant tissue placed in pure water.
Model answer
Water moves into the cells by osmosis, so the tissue gains mass and becomes firm.
- 4
Describe what happens to a piece of plant tissue placed in a concentrated sugar solution.
Model answer
Water moves out of the cells by osmosis, so the tissue loses mass and becomes limp.
- 5
How is the percentage change in mass of a piece of tissue calculated?
Model answer
Divide the change in mass by the starting mass and multiply by 100.
- 6
A potato cylinder of mass 4.0 g has a mass of 4.6 g after soaking. Calculate the percentage change in mass.
Model answer
A gain of 15%.
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