Exchange

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  • Created by: gsemma
  • Created on: 21-01-19 12:53
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  • Exchange
    • Fish
      • gas exchange in water requires gills
        • Operculum- bony plate that covers and protects gills
        • Gill filaments/ lamellae- thin rows of tissue (feathery and rich in oxygenated blood to very red) attached to bony arch- 2 per gill.
        • counter current flow- pumping deoxygenated blood in the opposite direction to water flow to maximise oxygen uptake.
        • Buccal cavity (mouth)- ventilate the gills by opening and closing the mouth to pump water over gills when not moving.
    • Insects
      • tracheal system
        • 1. air enters via spiracle pores and travels down the trachea into smaller tracheoles coated in tracheal fluid.
          • 2. exchange occurs though the fluid and tracheole walls
            • 3. sometimes ventilation is required so some areas are expended into air sacs for this purpose- contraction of thoracic, abdominal and flight muscles can change the vol of the sacs and act like bellows.
            • ways gasses are respired- diffusion gradient, mass transport and fluid filled tracheoles.
              • oxygen is used up and CO2 created by cells- 2 opposing diffusion gradients form lumen of tracheoles to body tissues of insect.
              • mass transport- contraction of abdomen and thorax muscles ventilate the tracheal system increasing exchange of gases.
              • fluid tracheoles- diffusion of gasses first into liquid phase and then into the body tissues is faster then gong straight form gas into body tissue.
      • limiting water loss
        • waterproof coating made of chitin
        • spircales at the opeinging of trachea can open and close when at rest.
    • general
      • larger organisms need specialised exchange surfaces compared to smaller animals witch can exchange over their bodily surfaces.
      • size- single cells organisms with a cytoplasm can use active transport and diffusion to exchange. Multicellular- have thick layers of tissue so the diffusion pathway is much too long for diffusion or active transport.
      • Surface area to volume ratio-       small organisms= large SA:V                    large organisms= small SA:V
      • good exchange surface will have- large SA, short diffusion pathway, good transport to the rest of the body, selective permeability and be able to maintain conc' gradient
    • leaves
      • transpiration
        • loss of water from leaves
          • prevented by having a waxy cuticle and guard cells around stomata (on underside- not directly exposed to sunlight) to open and close stomata.
            • prevents excess evaporation that can lead to wilting and desiccation.
              • the stomata are closed at night to stop transpiration when photosynthesis can no longer occur.
                • Deciduous plants loose leaves in winter when it is too cold for photosynthesis.
                • they close by- guard cell photosynthesis producing glucose- the water pot. is lower compared to surrounding cells- water moves across the conc' grad. into the guard cells making them turgid- opens the pore - this means stomata are open during daylight when the guard cells can photosynthesis.
      • structure- thin and many stomata for short diffusion pathway- large surface area fro exchange on outside of leaf and inside due to air spaces in spongy mesophyll.
        • Xerophytes- plants that live in dry conditions have adapted to cope with this by having rolled leaves to trap humidity and a thick way cuticle to prevent evaporation.
          • cacti and marram grass
        • Hydrophytes- very wet conditions- maximise sun exposure to produce enough oxygen due to limited supply and have large air spaces to keep afloat. also has hydathodes which allow the plan to produce water droplets allowing the plant to transpire in humid conditions.
          • water lilly
    • mammels
      • breathing ensures that the conc' of oxygen inside the lungs is higher than the CO2 in blood so it will diffuser across following the grad.
        • during inspiration- diaphragm contracts- lowering and  flattening it- external intercostal muscles contract rising the ribs- volume increases- pressure inside the chest is lower than outside so air moves in.
          • during expiration- diaphragm relaxes- pushed up- external intercostal relax and internal contract- volume decreases pushing the air out.
        • lungs
          • alveoli- very large surface area due to shear number of them- one cell thick and surrounded by capillaries so short diffusion pathway- caplliaies also thin so red blood cells pushed against wall so fast diffusion of O2 into blood.
            • exchange hear- reed blood cells slow down due to small area gaining more time for diffusion- ventilation maintains the conc' gradient so diffusion constantly occurs.
          • trachea and bronchi- wide enough fro unobstructed air flow- supported by cartilage rings to prevent collapse- lined with goblet cells and ciliate epithelial cells to trap and remove pathogens in mucus.
          • Bronchioles- no cartilage- wall is made of smooth muscle fibres and elastic fibres-m contraction of these muscles can slow air flow to protect the alveoli from harmful substances.
      • digestion
        • Oesophagus carries food from mouth to stomach.
          • Stomach secretes enzymes from glands to digest food.
            • the ileum further digests with enzymes and absorbs products of digestion into blood.
              • large intestine absorbs water and rectum stores faeces .
              • Chemical breakdown- hydrolysis of food with enzymes.
            • Physical breakdown- chewing and churning
        • carbs
          • saliva from salivary glands contain amylase which hydrolysis starch into maltose- pH neutral in the mouth.
            • in the stomach amylase is denatured and pancreatic amylase is secreted into Si to continue hydrolysis. Alkaline slat restore pH to neutral optimum.
              • in the ilium maltose brakes down maltose into glucose. the maltose is held in the cell-surface membrane of epithelial cells.
        • protein
          • endopepttidase- hydrolyses peptide bonds between amino acids in centre of proteins to produce several peptide chains.
            • Exopeptidase further breaks down these chains producing dipeptides ands amino acids
              • dipeptidase- membrane bound and hydrolyse the peptide bonds between dipeptides into single amino acids.
        • absorption
          • ileum's structure is adapted to this function due to its large SA due to many villi and microvilli. thin wall for short diffusion pathway and muscles to move food along the ileum maintaining the conc' gradient. well supplied with blood vessels for efficient diffusion and to carry nutrients a2way. a sodium potassium pump is used.
        • triglycerides
          • bile salts emuslfy monoglycerides and fatty acids into much smaller micelles. these breakdown on contact with epithelial cell-surface membranes. the non-polar monoglycerides and fatty acids diffuse through the membrane into he cells and recombine into trigcerides in the ER. combines with lacteals to lymphatic capillaries. chylomicrons pass from lymphatic vessels into blood and transported around the body.

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