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
Cell Level Systems
DNA structure: polymer, double helix and nucleotides
- 3 things to know
- Paper 7 (Biology)
Overview
What a polymer is, why DNA is a polymer built from nucleotides, how monomers and polymers differ, how the chain is built, and the two strands twisted into a double helix and why that shape stores genetic information stably.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Describe the difference between a monomer and a polymer, why a long chain can store so much information, and how DNA's chain is built.
Key term
What is meant by a polymer?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is meant by a polymer?
Model answer
A large molecule built from many smaller repeating units joined together in a long chain.
- 2
Why is DNA described as a polymer?
Model answer
It is a very long chain made from many repeating nucleotide units joined end to end.
- 3
Name the monomer units from which DNA is built.
Model answer
Nucleotides.
- 4
What is the difference between a monomer and a polymer?
Model answer
A monomer is one small unit, while a polymer is many monomers joined into a long chain.
- 5
Give one example of a biological polymer other than DNA.
Model answer
Starch, or a protein.
- 6
Why can a polymer built from only a few kinds of unit still store an enormous amount of information?
Model answer
The chain is extremely long, so the units can be arranged in a vast number of different orders.
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