Key term
OCR GCSE Biology A J247
Cell Level Systems
Topic overviewMicroscopy, and sub-cellular structuresDNA structure: polymer, double helix and nucleotidesEnzyme 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 mutationsAsexual 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, monitoring conservation and ecotourismFood 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 defencesWhite blood cells, antibodies and plateletsNon-specific defences and the immune systemVaccines, 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 brainHormones and the endocrine glandsHormones in reproduction and the menstrual cycleMethods of contraceptionTropisms, auxin and the roles of plant hormonesHomeostasis, and the skin in temperature controlInsulin and the control of blood glucoseType 1 and type 2 diabetesOsmotic changes in body fluids, and the kidneysKidney structure and the parts of the tubule
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
Organism Level Systems
Osmotic changes in body fluids, and the kidneys
- 3 things to know
- Paper 1
Overview
What happens to animal, red blood and plant cells in dilute and concentrated solutions, lysis, why blood concentration must stay steady, the kidneys' roles in controlling water and salt and removing urea made in the liver, how urine changes with water intake and on hot days, filtration and selective reabsorption, and the path of urine to the bladder.
What you need to know
Answer each one before you reveal it.
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Key term
What happens to a body cell placed in a solution with a lower water potential than its cytoplasm?
Key term
What happens to an animal cell placed in a solution more dilute than its own contents?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What happens to a body cell placed in a solution with a lower water potential than its cytoplasm?
Model answer
Water leaves the cell by osmosis, so the cell shrinks and cannot function properly.
- 2
What happens to an animal cell placed in a solution more dilute than its own contents?
Model answer
Water enters the cell by osmosis, so the cell swells and may burst.
- 3
What is lysis?
Model answer
The bursting of a cell when so much water has entered by osmosis that the membrane breaks.
- 4
What happens to a red blood cell placed in a very concentrated salt solution?
Model answer
Water leaves it by osmosis, so it shrinks and its surface becomes crinkled.
- 5
Why is there no change in size when a cell sits in a solution of the same concentration as its contents?
Model answer
Water moves into and out of the cell at the same rate, so there is no net movement either way.
- 6
Why can a plant cell survive being placed in pure water when an animal cell cannot?
Model answer
The plant cell has a strong cell wall that stops it swelling any further once it is full, while an animal cell has only a membrane and bursts.
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