Biology: B1 - Cell Structure and Transport Combined Science AQA

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  • Created by: AlyssaW
  • Created on: 02-05-18 16:04
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  • Biology: B1 - Cell Structure and Transport
    • The World of the Microscope
      • Light microscopes magnify up to about x2000, and have a resolving power of about 200nm.
      • Electron microscopes magnify up to about x2,000,000 and have a resolving power of around 0.2nm.
      • magnification =size of image size of real object
    • Animal and Plant Cells
      • Animal cell features common to all cells:
        • Nucleus
        • Cytoplasm
        • Cell membrane
        • Mitochondria
        • Ribosomes
      • Plant and algal cells contain all the structures seen in animal cells as well as a cellulose cell wall.
      • Many plant cells also contain chloroplasts and a permanent vacuole filled with sap.
    • Eukaryotic and Prokaryotic Cells
      • Eukaryotic cells all have a cell membrane, cytoplasm and genetic material enclosed in a nucleus.
      • Prokaryotic cells consist of cytoplasm and a cell membrane surrounded bu a cell wall.
        • The genetic material is not in a distinct nucleus. It forms a single DNA loop.
          • Prokaryotes may contain one or more extra small rings of DNA called plasmids.
        • Bacteria are all prokaryotes.
      • Bacteria are all prokaryotes.
    • Specialisation in Animal Cells
      • As an organism develops, cells differentiate to form different types of cells.
        • As an animal cell differentiates to from a specialised cell it acquires different sub-cellular structures.
          • These sub-cellular structures carry out a certain function.
            • Examples of specialised animal cells are:
              • Nerve cells
              • Muscle cells
              • Sperm cells
      • Animal cells may be specialised to function within:
        • Tissue
        • Organs
        • Organ systems
        • Whole Organisms
    • Specialisation in Plant Cells
      • Plant cells may be specialised to carry out a particular function.
        • Examples of specialised plant cells are:
          • Root Hair cells
          • Photo synthetic cells
          • Xylem cells
          • Phloem cells
      • Plant cells may be specialised to function in:
        • Tissue
        • Organ systems
        • Whole organisms
        • Organs
    • Diffusion
      • Diffusion is the spreading out of particles of any substance, in a solution or a gas.
        • This results in a net movement from an area of higher concentration to an area of lower concentration, down a concentration gradient.
        • Dissolved substances such as glucose and urea as well as gases such as oxygen and carbon dioxide, move in and out of cells by diffusion.
        • The rate of diffusion is affected by the difference in concentration, the temperature, and the available surface area.
      • The rate of diffusion is affected by the difference in concentration, the temperature, and the available surface area.
    • Osmosis
      • Osmosis is a special case of diffusion.
        • Diffusion
          • Diffusion is the spreading out of particles of any substance, in a solution or a gas.
            • This results in a net movement from an area of higher concentration to an area of lower concentration, down a concentration gradient.
            • Dissolved substances such as glucose and urea as well as gases such as oxygen and carbon dioxide, move in and out of cells by diffusion.
        • It is the movement of water from a dilute to a more concentrated solute solution through a partially permeable membrane that allows water to pass through.
      • Animal cells can be damaged if the concentration outside the cell changes dramatically.
      • Differences in the concentration of solutions inside and outside a cell cause water to move into or out of the cell by osmosis.
        • It is the movement of water from a dilute to a more concentrated solute solution through a partially permeable membrane that allows water to pass through.
    • Osmosis in Plants
      • Osmosis is important to maintain turgor in plant cells.
        • Osmosis is a special case of diffusion.
        • There are a variety of practical investigations that can be used to show the effect of osmosis on plant tissues.
          • Salt and sugar
          • Potato
          • Sweet potato and beetroot
      • Active Transport
        • Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient).
          • Active transport uses energy released from food in respiration to provide the energy required.
          • Allows plant root hairs to absorb mineral ions required for healthy growth from very dilute solutions in the soil against the concentration gradient.
          • Enables sugar molecules used for cell respiration to be absorbed from a  lower concentration in the gut into the blood where there is a higher concentration.
      • Exchanging Materials
        • Single-celled organisms have a relatively large surface area to volume ratio so all necessary exchanges with the environment take place over this surface.
        • In multicellular organisms, many organs are specialised with effective exchange surfaces.
        • Exchange surfaces usually have a large surface area and thin walls, which give short diffusion distances.
          • In animals, exchange surfaces will have an efficient blood supply or, for gaseous exchange, be ventilated.

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