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
Organisation
Root hair cells, xylem, phloem and stomata
- 3 things to know
- Biology Paper 1
Overview
Root hair cells taking up water by osmosis and mineral ions by active transport, the structure of xylem with lignin, the transpiration stream, stomata and guard cells, and phloem, translocation of sugars and how xylem and phloem differ.
What you need to know
Answer each one before you reveal it.
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Key term
What is lignin and what does it do in xylem?
Key term
What is meant by the transpiration stream?
Questions from this subtopic
Each one with the model answer underneath.
- 1
How is a root hair cell adapted for taking up water efficiently?
Model answer
It has a long thin hair that greatly increases the surface area in contact with the water in the soil.
- 2
By which process does water enter a root hair cell?
Model answer
Osmosis.
- 3
Explain why mineral ions enter root hair cells by active transport rather than by diffusion.
Model answer
The ions are already more concentrated inside the cell than in the soil, so they must be moved against the concentration gradient using energy from respiration.
- 4
What does xylem transport, and in which direction?
Model answer
Water and dissolved mineral ions, from the roots up to the stems and leaves.
- 5
Describe the structure of xylem tissue.
Model answer
It is made of dead cells joined end to end with their end walls gone, forming continuous hollow tubes.
- 6
What is lignin and what does it do in xylem?
Model answer
A tough substance deposited in the walls of xylem vessels that strengthens them and stops them collapsing.
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