Key term
OCR GCSE Combined Science Biology J250
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 mutationsHaploid, diploid and meiosisSingle gene inheritance and Punnett squaresSex determination and characteristics controlled by many genesVariation within a population, and classificationNatural selection and evolutionEvidence for evolution from fossils and antibiotic resistance
Global Challenges
Topic overviewField investigations, and human impact on ecosystemsMaintaining biodiversity, monitoring conservation and ecotourismSelective breeding and genetic engineeringHealth, disease, and types of diseaseInteractions between diseases, and how they spreadReducing the spread of disease, and named examplesWhite 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 arcHormonal coordination, thyroxine and adrenalineHormones in reproduction and the menstrual cycleContraception and treating infertilityHomeostasis and control systems in the bodyInsulin and glucagon in blood sugar controlType 1 and type 2 diabetes
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
Red blood cells and plasma
- 3 things to know
- Paper 7 (Biology)
Overview
The function of red blood cells, haemoglobin and oxyhaemoglobin, why red blood cells have no nucleus and a flattened disc shape and are small and flexible, what plasma is, the glucose, amino acids, urea and carbon dioxide dissolved in it, how plasma suits its transport role, and the cells, platelets and heat it also carries.
What you need to know
Answer each one before you reveal it.
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Key term
Why does a mature red blood cell have no nucleus?
Key term
Name four dissolved substances carried in plasma.
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is the function of a red blood cell?
Model answer
To carry oxygen from the lungs to the respiring cells of the body.
- 2
Which protein inside a red blood cell binds oxygen?
Model answer
Haemoglobin.
- 3
What is formed when haemoglobin combines with oxygen, and where does this happen?
Model answer
Oxyhaemoglobin is formed, in the lungs where the oxygen concentration is high.
- 4
Why does a mature red blood cell have no nucleus?
Model answer
Leaving it out makes room for more haemoglobin, so each cell can carry more oxygen.
- 5
How does the shape of a red blood cell help it carry oxygen?
Model answer
Its flattened, dimpled disc shape gives a large surface area for its volume, so oxygen diffuses in and out quickly.
- 6
Why is it useful that red blood cells are small and flexible?
Model answer
So they can squeeze through the narrowest capillaries and reach every tissue.
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