Science Biology Add Pt 1

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  • Plant & Animal Cells
    • Biology Add Pt1
      • Diffusion
        • Cells & Diffusion
          • Diffusion is the spreading of the particles of a gas, or of any substance in solution
            • Resulting in a net movement from a region where they are of higher concentration, into a region where they are in a lower concentration.
          • Most cells need oxygen so that they can respire.
            • Oxygen diffuses into the cells from a higher concentration outside to a lower concentration inside.
          • The concentration of oxygen inside a cell is kept low because the cell keeps on using it up.
        • A Model Cell
          • Visking tubing contains millions of tiny holes which only let small molecules like water diffuse through.
            • Large molecules, such as starch, cannot cross the membrane. We say it is partially permeable.
          • This is similar to a cell membrane. Visking tubing can therefore be used as a model of a cell
      • Specialised Cells
        • The Human body contains hundreds of different kinds of specialised cells
          • Red Blood Cells
          • Goblet Cells
          • Ciliated Cells
        • Specialised Plant Cells
          • Root-hair cells are specialised plant cells
            • They are fine hair-like extensions of a root.
            • Their large surface area enables plants to maximise their absorption of water from the soil.
      • Photosynthesis
        • The word of equation for photosynthesis is:
          • carbon dioxide + water (+ light energy)    ?    glucose + oxygen
        • Chlorophyll and light absorption
          • White light is a continuous spectrum of colours, from red to violet
            • Different parts of the spectrum have their own characteristic wavelengths
              • Short wavelength light looks blue
              • Long wavelength light looks red
            • Chlorophyll looks green because it bsorbs the blue and red parts of the spectrum and reflects the green part
          • Light energy is absorbed by chlorophyll of plant cell
        • In photosynthesis light energy is stored in glucose molecules
          • Glucose can be converted into starch and stored for later use.
            • Starch molecules are big and unlike glucose cannot diffuse out of cells.
        • The energy is transferred to animals when they eat the plants.
    • Animal Cells
      • Nucleus
        • A large substance inside the cell. It contains chromosomes made of DNA. The nucleus controls the activities of the cell.
      • Cytoplasm
        • A jelly-like substance containing many chemicals most of the chemical reactions of the cell occur here
      • Cell Membrane
        • A thin layer around the cell. It controls the movement of substances into and out of the cell.
      • Mitochondria
        • Small rod-shaped structures that release energy from sugar during aerobic respiration
      • Ribosomes
        • Small ball shaped structures in the cytoplasm where proteins
    • Plant Cells
      • Chloroplasts
        • Small discs found in the cytoplasm. They contain the green pigment chlorophyll. Chlorophyll traps light energy for photosynthesis.
      • Cell Wall
        • A layer outside the cell membrane. It is made of cellulose, which is strong and supports the cell.
      • Permanent Vacuole
        • A fluid filled cavity. The liquid inside is called cell sap. The sap helps support the cell.


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