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
the-endocrine-system
The endocrine system
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A hormone is a chemical substance produced by an endocrine gland and carried by the blood
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They are chemicals which transmit information from one part of the organism to another and bring about a change
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They alter the activity of one or more specific target organs
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Hormones are used to control functions that do not need instant responses
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The endocrine glands that produce hormones in animals are known collectively as the endocrine system
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A gland is a group of cells that produces and releases one or more substances (a process known as secretion)
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Hormones such as insulin, glucagon, ADH and adrenaline are cell-signalling molecules that are released into the blood
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Endocrine glands have a good blood supply because, when they make hormones, they need to get the hormones into the bloodstream (specifically the blood plasma) as soon as possible so they can travel around the body to the target organs to bring about a response
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Hormones only affect cells with receptors that the hormone can bind to
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These are either found on the cell surface membrane or inside cells
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Receptors have to be complementary to hormones for there to be an effect
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Hormones such as insulin, glucagon and ADH are peptides or small proteins
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They are water-soluble and so cannot cross the phospholipid bilayer of cell surface membranes
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These hormones bind to receptors on the cell surface membranes of their target cells, which activates second messengers to transfer the signal throughout the cytoplasm
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Hormones such as testosterone, oestrogen and progesterone are steroid hormones
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They are lipid-soluble and so can cross the phospholipid bilayer
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These hormones bind to receptors in the cytoplasm or nucleus of their target cells
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