biology 3

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  • Biology
    • Osmosis
      • type of diffusion
        • movement of water from DILUTE (aq) to CONCENTRATED (aq)
        • through partially permeable membrane
          • small molecules only
      • demonstrated by visking tubing
      • water molecules move about, hit the walls, and go through the holes.
      • water flows to the more concentrated side
      • Animal cells in:
        • more  concentrated (aq) than cytoplasm, water leaves and cell shrinks
        • less concentrated (aq) than cytoplasm, water enters and cell bursts
      • Plant cells in:
        • more concentrated (aq) than cytoplasm, water leaves cell and membrane moves away from cell wall
        • less concentrated (aq) than cytoplasm, water enters and membrane pushes against cell wall
    • Active Transport
      • requires energy from cell respiration
        • comes from mitochondria-breaks down glucose & combines them with oxygen to release energy
      • molecules move against concentration gradient
      • dilute to concentrated
      • used by root cells to absorb minerals
        • oxygen from airs spaces in the soil
      • proteins in membrane transport molecules from surroundings into cells
    • Exchange surfaces
      • take substances from surroundings & remove others
      • lungs- alveoli absorb oxygen and release CO2
      • s.intestines- villi absorb nutrients from food
        • proteins for active transport absorb nutrients against concentration gradient
      • kidneys- nephrons remove urea from blood
      • for efficient exchange, they have:
        • large surface area
        • small distance for diffusion
        • movement to maintain concentration gradient
    • Gas exchange
      • oxygen diffuses in to blood, CO2 diffuses out.
        • happens in alveoli in the lungs
          • air to reach alveoli passes through trachea, bronchi & bronchioles
      • alveoli & capillaries only 1 cell thick- short distance for diffusion
      • movement of blood & ventilation maintains the c-gradient for diffusion
      • singe celled organisms have a large s.a:volume don't need a ventilation system.
        • multicellular organisms have small s.a:volume so need specially adapted gas exchange surfaces
    • Breathing
      • inspired air: breathed in
      • expired air: breathed out
      • air pushed in & out by muscles in-between ribs  & diaphragm
    • Blood
      • platelets: blood clotting
      • plasma: pale, yellow liquid, carries dissolved nutrients and waste
      • red blood cells contain haemoglobin-carries oxygen
        • haemoglobin oxygen= oxyhaemoglobin
      • when blood passes through:
        • lungs: CO2 diffuses out, oxygen diffuses in
        • s.intestines: absorbs nutrients
        • kidneys: urea diffuses out
    • Transport in plants
      • xylem: water from roots to leave & stem
        • loss of water reduces xylem pressure
        • made up of dead cells & is hollow
      • phloem: dissolved sugars from leaves to everywhere else
      • water moves through plants via transpiration stream
        • roots to leaves
        • water enters through osmosis and leaves through xylem tissue
      • photometer measures transpiration.
        • hot, dry & windy places increase rate of transpiation
    • Waste & water control
      • CO2 is waste from respiration.  removed by lungs
      • urea is waste from excess amino acids in liver. removed by kideys
        • kidneys filter blood, absorb everything (not ions or big molecules)
          • glucose is reabsorbed leaving urea, excess water and ions.
    • Temperature control
      • thermoregulatory centre in brain controls body temperature
      • temperature sensors on the skin detect if you're too cold/hot
        • too hot: skin arterioles dilate, more blood to the surface & energy is lost via radiation.
          • sweat evaporates and we cool down
        • too cold: skin arterioles contract, blood is kept far away from the skin & muscles contract to generate heat needed for respiration
    • Blood glucose
      • pancreas detects if levels are too high and secretes insulin.
      • liver cells store glucose as glycogen (insoluble)
        • when levels drop pancreas releases glucogan, causing liver to break down glycogen and release to blood
  • phloem: dissolved sugars from leaves to everywhere else

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