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
- 9 subtopics
- 27 things to know
- Paper 7 (Biology)
What Scaling Up covers
Scaling Up is examined in Paper 7 (Biology). It covers diffusion, osmosis and active transport; mitosis, the cell cycle and cell differentiation; stem cells in animals and meristems in plants; surface area to volume ratio and exchange surfaces; the circulatory system, the heart and blood vessels; red blood cells and plasma; root hair cells, transpiration and translocation; xylem and phloem; and factors affecting water uptake and the potometer.
Where it is assessed
Paper 7 (Biology)
Combined Science A, Paper 7 (Biology): 1 hour 10 minutes, 60 marks, 16.7% of the qualification.
Check the OCR specification ↗The 9 subtopics
Each one has its own page.
- Diffusion, osmosis and active transportWhat diffusion is and why it needs no energy, osmosis and water potential, a plant cell in salt solution, and active transport against a gradient in root hairs and the gut.Open →
- Mitosis, the cell cycle and cell differentiationThe stages of the cell cycle, DNA replication and why cells grow first, what happens to chromosomes in mitosis and the two identical cells it makes, its roles in growth, repair and asexual reproduction, what cell differentiation is and why it makes organisms efficient, how sperm, nerve, muscle and palisade cells are specialised, how plant and animal cells differ in keeping that ability, and reading percentiles on growth charts.Open →
- Stem cells in animals and meristems in plantsWhat stem cells are and where embryonic and adult stem cells are found, what meristems are and where they occur, how stem cells and meristems allow development, growth and repair, bone marrow stem cells replacing blood cells, growing a plant from a cutting, how embryonic and adult stem cells differ, why embryonic stem cells are useful yet controversial, and treating a patient with their own stem cells.Open →
- Surface area to volume ratio and exchange surfacesCalculating the surface area, volume and surface area to volume ratio of cubes and blocks, how the ratio falls as organisms get larger, why single-celled organisms rely on diffusion while large animals need exchange surfaces and transport systems, what makes an exchange surface efficient, and the oxygen, carbon dioxide, urea, water, food molecules and mineral ions that organisms take in, transport or remove.Open →
- The circulatory system, the heart and blood vesselsThe job of the circulatory system, the double circulation and its two circuits, its link to gas exchange, the order of arteries, arterioles, capillaries and veins, the four chambers of the heart and the vessels entering and leaving it, the tricuspid, bicuspid and semilunar valves, the thicker left ventricle wall, cardiac muscle, and how arteries, veins and capillaries are adapted to their functions.Open →
- Red blood cells and plasmaThe 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.Open →
- Root hair cells, transpiration and translocationWhere 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.Open →
- Xylem and phloemWhat xylem and phloem transport and in which direction, the structure of a xylem vessel, lignin and why dead empty xylem cells help, sieve plates, living sieve tube cells and their companion cells, why transport in phloem needs energy, and how movement in phloem differs from movement in xylem.Open →
- Factors affecting water uptake, and the potometerHow light, temperature, air movement and humidity change the rate of water uptake, why plants wilt on a hot windy day, and using a potometer to measure and calculate the rate.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Name each ventricle's outflow vessel and its destination, the valves between the atria and ventricles, the valves at the ventricle exits, and what valves do.
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What happens to the chromosomes when DNA is replicated, what does one round of mitosis produce, and what is mitosis for in a multicellular organism?
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Name one substance that diffuses into a respiring cell and one that diffuses out of it.
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Name two places in an adult human where stem cells are found.
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Name three features that make an exchange surface efficient.
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What is formed when haemoglobin combines with oxygen, and where does this happen?
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How does the shape of a root hair cell suit it to absorbing water?
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Why does a plant still take up some water in the dark?
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In terms of water potential, in which direction does water move between two solutions?
Process
List the stages of the cell cycle in order.
Key term
Which cells in a plant play the role that stem cells play in an animal?
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Why does an organism need water transported around it?
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Name the two circuits that make up a mammal's circulation.
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Why does a mature red blood cell have no nucleus?
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Explain why water moves into a root hair cell.
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What does xylem transport, and in which direction?
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Explain why a plant may wilt on a hot, windy day.
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Which has the higher water potential, pure water or a concentrated sugar solution?
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What happens to the chromosomes during DNA replication?
Process
Name the three processes in an organism that stem cells make possible.
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In what form are food molecules carried around an animal's body?
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Which vessels carry blood away from the heart and which return it?
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Name four dissolved substances carried in plasma.
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Name a mineral ion taken up from the soil and say what the plant uses it for.
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What does phloem transport, and where does it come from?
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Why does increasing the light beyond a certain brightness stop increasing water loss?
Take Scaling Up further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Osmosis vs Active transport
Osmosis: movement of water from higher to lower water potential across a membrane. Active transport: movement of a substance against its concentration gradient using energy from respiration.
Artery vs Vein
Artery: thick-walled vessel with a narrow lumen carrying blood away from the heart. Vein: thin-walled vessel with a wide lumen and valves returning blood to the heart.
Xylem vs Phloem
Xylem: dead hollow vessels carrying water and mineral ions upwards. Phloem: living sieve tubes carrying dissolved sugars up and down the plant.
Questions from this topic
Each one with the model answer underneath.
- 1
What is diffusion?
Model answer
It is the net movement of particles from where they are more concentrated to where they are less concentrated, down a concentration gradient.
- 2
Does a cell have to use energy from respiration to move a substance in by diffusion?
Model answer
No, diffusion is a passive process driven by the random movement of the particles themselves.
- 3
Name one substance that diffuses into a respiring cell and one that diffuses out of it.
Model answer
Oxygen diffuses in and carbon dioxide diffuses out.
- 4
What is osmosis?
Model answer
It is the movement of water across a partially permeable membrane, from a dilute solution to a more concentrated one.
- 5
In terms of water potential, in which direction does water move between two solutions?
Model answer
Water moves from the solution with the higher water potential to the solution with the lower water potential.
- 6
Which has the higher water potential, pure water or a concentrated sugar solution?
Model answer
Pure water, because dissolving sugar in water lowers its water potential.
What is inside Levo
Six ways to work the same material.
Scaling Up revision questions
- What does Scaling Up cover in OCR GCSE Combined Science Biology?
- 9 subtopics: diffusion, osmosis and active transport, mitosis, the cell cycle and cell differentiation, stem cells in animals and meristems in plants, surface area to volume ratio and exchange surfaces, the circulatory system, the heart and blood vessels, red blood cells and plasma, root hair cells, transpiration and translocation, xylem and phloem and factors affecting water uptake, and the potometer. Each one has its own page with questions and model answers.
- How is Scaling Up organised?
- By the OCR J250 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Scaling Up, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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