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BIOLOGY CHAPTER 3, BIOLOGY CHAPTER 4 - Coggle Diagram

- - - - When a cell uses oxygen for its aerobic respiration. the concentration of oxygen inside the cell fails and so oxygen molecules diffuse into the cell until the concentration is raised again. During tissue respiration, carbon dioxide is produced and so its concentration inside the cell increases.
        
        Once again diffusion takes place, but this time the molecules move out of the cell. In this way, diffusion can explain how a cell takes in its oxygen and gets rid of its carbon dioxide.
      - DIFFUSION OF SUBSTANCES
        
        The importance of diffusion of gases and solutes
        
        Gases
        
        Most living things need a reliable source of oxygen for respiration. This moves into the organism by diffusion down a concentration gradient. Small animals with a large surface area to volume ratio may art oxygen through their body surface. Larger animals need gas exchange organs like lungs or gill which provide a large surface area for gas exchange. They also need a circulatory system to move the oxygen to all their cells. Carbon dioxide, produced during aerobic respiration, can be toxic if it builds up. It is removed in the same way, by diffusion.
        
        Photosynthetic plants need carbon dioxide for making their food. This diffuses through the stomata in the leaves into the air spaces in the mesophyll, before reaching the palisade cells. Oxygen produced during photosynthesis, as well as water vapour from the transpiration stream, diffuses out of the leaf through the stomata. The rate of diffusion of water vapour depends on the temperature, humidity and wind speed. Any oxygen needed for respiration (some is produced by photosynthesis) and carbon dioxide produced (some is used up by photosynthesis) also diffuses through the stomatal of the leaves.
        
        EXAMPLE
        In the ileum, water-soluble vitamins like vitamin C are absorbed into the bloodstream by diffusion. In the kidneys, some solutes, like urea and minerals and ions, pass back into the bloodstream by diffusion. At first, glucose is reabsorbed by diffusion, but active transport is also involved.
- - - - In living cells, the cell membrane is partially permeable and the cytoplasm and vacuole (in plant cells) contain dissolved substances. As a result, water tends to diffuse into cells by osmosis if they are surrounded by a weak solution (e.g. fresh water). If the cells are surrounded by a stronger solution (e.g. sea water), the cells may lose water by osmosis. These effects are described more fully later.
        
        When a substance such as sugar dissolves in water, the
        
        sugar molecules attract some of the water molecules
        
        and stop them moving freely. This, in effect, reduces
        
        the concentration of water molecules
        
        the sugar molecules on the right have ‘captured’
        
        half the water molecules. There are more free water
        
        molecules on the left of the membrane than on the
        
        right, so water will diffuse more rapidly from left to
        
        right across the membrane than from right to left.
        
        The partially permeable membrane does not act like
        
        a sieve in this case.
    - - cells are surrounded by a solution which is more concentrated than the cytoplasm, water will pass out of the cell by osmosis and the cell will shrink, Too much uptake or loss of water by osmosis may damage cells. For this reason, it is very important that the cells in an animal's body are surrounded by a liquid which has the same concentration as the liquid inside the cells. In vertebrates, the brain monitors the concentration of the blood and the kidneys adjust it. By keeping the blood concentration within narrow limits, the concentration of the tissue fluid remains constant. So, cells are not swollen by taking in too much water or dehydrated by losing too much.
    - - is like the vacuole. If enough air is pumped in, it pushes the inner tube against the tyre and makes the tyre hard. When plant cells have absorbed a maximum amount of water by osmosis they become very rigid, due to the pressure of water pressing outwards on the cell wall. As a result, the stems and leaves are supported. If the cells lose water, there is no longer any water pressure pressing outwards against the cell walls. So, the stems and leaves are not supported any more. At this point, the plant becomes limp and wilts
      - A plant cell with the vacuole pushing out on the cell
      - wall is said to be turgid and the vacuole is exerting
      - turgor pressure on the inelastic cell wall.
      - If all the cells in a leaf and stem are turgid, the
      - stem will be firm and upright and the leaves held out
      - straight. If the vacuoles lose water for any reason, the
      - Osmosis is the net movement of water molecules from a
      - region of higher water potential (a dilute solution) to a
      - region of lower water potential (a concentrated solution)
      - through a partially permeable membrane.
      - cells will lose their turgor and become flaccid.
    - - WATER POTENTIAL:
        
        The water potential of a solution is a measure of
        
        whether it is likely to lose or gain water molecules
        
        from another solution.
      - Active Transport
        
        Key definitions:
        Active transport is the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration li.e. against a concentration gradient) using energy from respiration.
        
        it cannot take place without respiration because it constantly needs energy through respiration . handset contains a large amount of mitochondria
        
        it is mostly present in places such as the villi of the intestine
        
        here the concentration in the medium is low but the capillaries within as a high concentration hence it goes from the lower region of constitution to a larger concentration level
        
        the conformation is the change in the shape of the karao protein when a molecular attaches itself to carry a protein a long with one or more ATP which is adenosine dry phosphate this conformation change releases the molecule that attached once the molecule is released the carrier transport comes back to its original conformation
        
        the ATP acts like a pump for ions
        
        The importance of active
        transport
        If diffusion was the only way a cell could take in substances, it would have no control over what went in or out. Anything that was more concentrated outside would diffuse into the cell even if it was harmful. Substances which the cell needed would diffuse out as soon as their concentration inside the cell increased above their concentration outside it. However, the cell membrane has a lot of control over the substances which enter and leave the cell.
- - - - GLUCOSE SINGULAR, MALTOSE- TWO OR MORE PAIR OF GLUCOSE