Biology_A-level_Cie
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1-1-the-microscope-in-cell-studies5 主题
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1-2-cells-as-the-basic-units-of-living-organisms5 主题
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2-1-testing-for-biological-molecules3 主题
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2-2-carbohydrates-and-lipids8 主题
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2-3-proteins6 主题
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2-4-water2 主题
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3-1-mode-of-action-of-enzymes5 主题
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3-2-factors-that-affect-enzyme-action8 主题
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4-1-fluid-mosaic-membranes4 主题
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4-2-movement-into-and-out-of-cells12 主题
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diffusion
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osmosis
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active-transport
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endocytosis-and-exocytosis
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investigating-transport-processes-in-plants
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investigating-diffusion
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surface-area-to-volume-ratios
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investigating-surface-area
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estimating-water-potential-in-plants
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osmosis-in-plant-cells
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osmosis-in-animals
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comparing-osmosis-in-plants-and-animals
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diffusion
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5-1-replication-and-division-of-nuclei-and-cells6 主题
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5-2-chromosome-behaviour-in-mitosis2 主题
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6-1-structure-of-nucleic-acids-and-replication-of-dna4 主题
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6-2-protein-synthesis5 主题
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7-1-structure-of-transport-tissues4 主题
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7-2-transport-mechanisms7 主题
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8-1-the-circulatory-system7 主题
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8-2-transport-of-oxygen-and-carbon-dioxide5 主题
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8-3-the-heart4 主题
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9-1-the-gas-exchange-system6 主题
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10-1-infectious-diseases3 主题
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10-2-antibiotics3 主题
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11-1-the-immune-system4 主题
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11-2-antibodies-and-vaccination6 主题
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12-1-energy5 主题
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12-2-respiration11 主题
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aerobic-respiration-the-krebs-cycle
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aerobic-respiration-role-of-nad-and-fad
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aerobic-respiration-oxidative-phosphorylation
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anaerobic-respiration
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energy-yield-aerobic-and-anaerobic-respiration
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anaerobic-adaptation-of-rice
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aerobic-respiration-effect-of-temperature-and-substrate-concentration
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structure-and-function-of-mitochondria
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the-four-stages-in-aerobic-respiration
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aerobic-respiration-glycolysis
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aerobic-respiration-the-link-reaction
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aerobic-respiration-the-krebs-cycle
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13-1-photosynthesis-as-an-energy-transfer-process8 主题
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13-2-investigation-of-limiting-factors2 主题
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14-1-homeostasis-in-mammals8 主题
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14-2-homeostasis-in-plants3 主题
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15-1-control-and-coordination-in-mammals12 主题
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the-endocrine-system
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the-nervous-system
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neurones
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sensory-receptor-cells
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sequence-of-events-resulting-in-an-action-potential
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transmission-of-nerve-impulses
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speed-of-conduction-of-impulses
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the-refractory-period
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cholinergic-synapses
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stimulating-contraction-in-striated-muscle
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ultrastructure-of-striated-muscle
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sliding-filament-model-of-muscular-contraction
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the-endocrine-system
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15-2-control-and-coordination-in-plants3 主题
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16-1-passage-of-information-from-parents-to-offspring5 主题
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16-2-the-roles-of-genes-in-determining-the-phenotype7 主题
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16-3-gene-control3 主题
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17-1-variation4 主题
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17-2-natural-and-artificial-selection7 主题
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17-3-evolution2 主题
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18-1-classification5 主题
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18-2-biodiversity7 主题
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18-3-conservation6 主题
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19-1-principles-of-genetic-technology11 主题
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19-2-genetic-technology-applied-to-medicine4 主题
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19-3-genetically-modified-organisms-in-agriculture2 主题
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1-1-the-microscope-in-cell-studies
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1-2-cells-as-the-basic-units-of-living-organisms
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2-1-testing-for-biological-molecules
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2-2-carbohydrates-and-lipids
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2-3-proteins
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2-4-water
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3-1-mode-of-action-of-enzymes
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3-2-factors-that-affect-enzyme-action
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4-1-fluid-mosaic-membranes
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4-2-movement-into-and-out-of-cells
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5-1-replication-and-division-of-nuclei-and-cells
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5-2-chromosome-behaviour-in-mitosis
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6-1-structure-of-nucleic-acids-and-replication-of-dna
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6-2-protein-synthesis
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7-1-structure-of-transport-tissues
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7-2-transport-mechanisms
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8-1-the-circulatory-system
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8-2-transport-of-oxygen-and-carbon-dioxide
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8-3-the-heart
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9-1-the-gas-exchange-system
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10-1-infectious-diseases
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10-2-antibiotics
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11-1-the-immune-system
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11-2-antibodies-and-vaccination
recognising-structures
Recognising structures in the gas exchange system
Trachea
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A tracheal cross-section shows the large lumen, which air has to travel through
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The innermost cells of the trachea are the ciliated epithelia with projections called cilia
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The cells of the ciliated epithelium are shown in the light micrograph below
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The cells are tightly packed and interspersed with goblet cells, which are shown in light grey
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The density of the cilia are shown in the electron micrograph below
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The cilia are essential for sweeping bacteria and dust-filled mucus away from the lungs and up the trachea into the back of the mouth
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This mucus is then swallowed, with any pathogens hopefully destroyed by the acidic conditions in the stomach
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Bronchi
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Bronchi are distinctive from the trachea because their lumen is narrower (around 8-9mm instead of 18mm
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However, like the trachea, they are lined by ciliated epithelium
Bronchioles
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Bronchioles are approximately 1mm or less in diameter
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Smooth muscle and cuboidal epithelium are found in their walls
Alveoli
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Alveoli have a sponge-like appearance under a microscope due to their air spaces.
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They are surrounded by an extensive capillary network and are lined by squamous epithelium
Walls of the trachea and bronchus
Trachea
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The tracheal lumen is around 15 to 20 mm and is lined by ciliated epithelia
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The tracheal wall is surrounded by strong and flexible cartilage which flexes during breathing
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The smooth muscle of the trachea constricts and allows air to be expelled with more force