Biology 3a Mindmap (incomplete)

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  • Biology 3a
    • Osmosis
      • Osmosis is a Special Case of Diffusion that only applies to water
      • Osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low concentration
      • Water moves into and out of cells by Osmosis
        • Osmosis restores balance in both cases, should it become too dilute or too concentrated
      • A DILUTE solution has a high concentration of SOLVENT. It has a LOW concentration of the SOLUTE
    • Gas and Solute Exchange
      • Substances move by DIFFUSION, OSMOSIS and ACTIVE TRANSPORT
        • Diffusion is where particles move from an area of HIGH concentration to LOW concentration
        • Osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low concentration
        • Active Transport is where particles move from an area of LOW concentration to HIGH concentration
      • The bottom of leaves is an EXCHANGE SURFACE. It's covered in STOMATA
        • Oxygen (produced via photosynthesis) and water vapour also diffuse out through the stomata
          • The size of the stomata is controlled by GUARD CELLS. These close the stomata if the plant is losing water faster than it gains water.
      • Adaptations for exchanging materials
        • Large surface area
        • Thin, thus short diffusion path
        • An efficient blood supply
          • Moves the diffusing substances away, maintains a concentration (diffusion) gradient
        • Being ventilated
          • To make gaseous exchange more efficient; maintains steep concentration gradients
    • The Breathing System
      • The Lungs are in the Thorax
      • Ventilation is breathing in and breathing out
        • Breathing in
          • Intercostal muscles and diaphragm contract
            • Thorax volume increases
              • This decreases the pressure, drawing air in
        • Breathing Out
          • Intercostal muscles and diaphragm
            • Thorax volume decrease
              • This increases the pressure, so air is forced out
      • Artificial Ventilators
        • These are machines that move air into and out of the lungs.
          • An iron lung used to be used as an artificial ventilator
            • Nowadays, most artificial ventilators work by pumping air into the lung (like a balloon)
    • Diffusion Through Cell Membranes
      • Gas Exchange Happens in the Lungs
        • 1) The lungs transfer oxygen to the blood and remove waste carbon dioxide
          • 2) To do this the lungs containt millions of air sacs (alveoli) where the gas exchange takes place
            • 3) The alveoli are specialised to maximise the diffusion of oxygen and carbon dioxide. They have an enormous surface area and very thin walls
      • The Villi provide a really big surface area
        • 1) The inside of the small intestine is covered in millions and millions of these tiny projections called villi
          • 2) They increase the surface area in a big way so that digested food is absorbed much more quickly into the blood
            • 3) Notice they have: a single layer of surface cells; a very good bloody supply to assist quick absorption
    • Active Transport
      • Root hairs are specialised for absorbing water and minerals
        • 1) The cells on the surface of plant roots grown into long "hairs" which stick out into soil
          • 2) This gives the plant a big surface area for absorbing water and mineral ions from the soil
            • 3) Most of the water and mineral ions that get into a plant are absorbed by the root hair cells
      • Root hairs take in minerals using active transport
        • 1) Active transport allows the plant to absorb minerals from a very dilute solution, against a concentration gradient. Active transport needs energy from respiration to make it work
          • 2) Active transport also happens in humans, for example in taking glucose from the gut and from the kidney tubules
      • We need active transport to stop us starving
        • Active transport is used in the gut when there is a low concentration of nutrients in the gut, but a high concentration of nutrients in the blood
        • 1) When there's a higher concentration of glucose and amino acids in the gut they diffuse naturally into the blood
          • 2) Sometimes there's a lower concentration of nutrients in the gut than there is in the blood.
            • 3) This means that the concentration gradient is the other way. Therefore, active transport is used
              • 4) Active transport allows nutrients to be taken into the blood, despite the fact the concentration gradient is the other way
    • Water Flow Through Plants
      • Phloem tubes transport food
        • 1) Made of columns of living cells with small holes in the ends to allow things to flow through
          • 2) They transport food substances (mainly dissolved sugars) made in the leaves to growing regions (e.g. new shoots) and storage organs of the plant
            • 3) The transport goes in both directions
      • Xylem tubes take water up
        • 1 Made of dead cells joined end to end with no end walls between them and a hole down the centre
          • 2) They carry water and minerals from the roots to the steam and leaves in the transpiration stream
      • Transpiration is the loss of water from the plant
        • 1) Transpiration is caused by the evaporation and diffusion of water from inside the leaves
          • 2) This creates a shortage of water in the leaf and as a result more water is drawn up from the rest of the plant through the xylem vessels to replace it
            • 3) This means more water is drawn up from the roots and as such there's a constant transpiration stream of water through the plant
    • Circulatory System
      • The Heart
        • Human hearts have a double circulatory system - two circuits joined together
        • The heart contracts to pump blood around the body
          • 1) The heart is a pumping organ that keeps the blood flowing around the body. The walls of the heart are mostly made of muscle tissue.
            • 2) The heart has valves to make sure that blood goes the in the right direction - they prevent it from flowing backwards
        • Double Circulatory System
          • 1) The first one pumps DEOXYGENATED BLOOD (blood without oxygen) to the lungs to take in OXYGEN. The blood then returns to the heart.
            • 2) The second one pumps oxygenated blood around all the other organs of the body.The blood gives up its oxygen at the body cells and the deoxygenated blood returns to the heart to be pumped out the lungs again
        • How the heart works
          • 1) Blood flows into the atria from vena cava and the pulmonary vein
            • 2) The atria contract, forcing the blood into the pulmonary artery and the aorta and out of the heart
              • 3) The ventricles contract, forcing the blood into the pulmonary artery and the aorta and out of the heart
                • 4) The blood then flows to the organs though arteries and returns through veins
                  • 5) The atria fill again and the whole cycle starts over

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