Key term
OCR GCSE Biology A J247
Cell Level Systems
Topic overviewMicroscopy, and sub-cellular structuresDNA structure: polymer, double helix and nucleotidesProtein synthesis and the triplet codeEnzyme action, and investigating enzymesCellular respiration as an exothermic processAerobic and anaerobic respiration comparedSynthesis and breakdown of carbohydrates, proteins and lipidsPhotosynthesis: producers and the processPhotosynthesis as endothermic, and investigating itLimiting factors in photosynthesis
Community Level Systems
Genes, Inheritance and Selection
Topic overviewGenetic terms, and the genomeGenome, environment and mutationsHow genetic variants influence phenotypeAsexual and sexual reproduction comparedHaploid, diploid and meiosisSingle gene inheritance and Punnett squaresSex determination, multiple genes and Mendel's workVariation within a population, and classificationNatural selection and evolutionEvidence for evolution, and the work of Darwin and Wallace
Global Challenges
Topic overviewField investigations, and human impact on ecosystemsMaintaining biodiversity, and evidence for environmental changeFood security, agricultural and biotechnological solutionsSelective breeding and genetic engineeringHealth, disease, and types of diseaseInteractions between diseases, and how they spreadReducing the spread of disease, and named examplesPhysical and chemical plant defencesDetecting plant disease; white blood cells and plateletsNon-specific defences and the immune systemMonoclonal antibodies and their usesVaccines, medicines and aseptic techniqueDeveloping new medicines, and non-communicable diseaseTreating cardiovascular disease, and lifestyle factorsCancer, and the use of stem cells in medicineGene technology in medicine, and the human genome
Organism Level Systems
Topic overviewThe nervous system and coordinated responsesThe reflex arcThe eye and its common defectsThe structure and function of the brainInvestigating and treating the brainHormonal coordination, thyroxine and adrenalineHormones in reproduction and the menstrual cycleContraception and treating infertilityPlant hormones and their commercial usesHomeostasis, and the skin in temperature controlInsulin and glucagon in blood sugar controlType 1 and type 2 diabetesOsmotic changes in body fluids, and the kidneysThe kidney tubule and the effect of ADHResponding to temperature and osmotic challenges
Scaling Up
Topic overviewDiffusion, osmosis and active transportMitosis, the cell cycle and cell differentiationStem cells in animals and meristems in plantsSurface area to volume ratio and exchange surfacesThe circulatory system, the heart and blood vesselsRed blood cells and plasmaRoot hair cells, transpiration and translocationXylem and phloemFactors affecting water uptake, and the potometer
Scaling Up
Root hair cells, transpiration and translocation
- 3 things to know
- Paper 3
Overview
Where root hair cells are and how their shape helps, water entering by osmosis and mineral ions by active transport, transpiration through the stomata and guard cells, and translocation of sugars.
What you need to know
Answer each one before you reveal it.
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Key term
Explain why water moves into a root hair cell.
Key term
Name a mineral ion taken up from the soil and say what the plant uses it for.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Where on a root are the root hair cells found?
Model answer
In a zone just behind the growing tip of each root.
- 2
How does the shape of a root hair cell suit it to absorbing water?
Model answer
A long, thin extension pushes out between the soil particles and gives the cell a very large surface area for absorption.
- 3
By which process does water enter a root hair cell?
Model answer
Osmosis.
- 4
Explain why water moves into a root hair cell.
Model answer
The cell sap is more concentrated than the water in the soil, so water moves down the water potential gradient into the cell.
- 5
By which process are mineral ions taken into a root hair cell?
Model answer
Active transport.
- 6
Explain why mineral ions cannot simply diffuse into a root hair cell.
Model answer
They are usually more concentrated inside the cell than in the soil water, so they have to be moved against the concentration gradient.
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