Biology - Cells

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  • Cells
    • Animal cells
      • Nucleus - contains genetic material that controls the activities of the cell.
      • Cytoplasm  - gel-like substance where most of the chemical reactions happen. Contains enzymes that control these chemical reactions.
      • Cell Membrane - holds the cell together and controls what goes in and out.
      • Mitochondria - not the powerhouse of the cell! xD They are where most of the reactions for respiration take place.
      • Ribosomes - These are where proteins are made.
    • Plant Cells
      • Plant cells usually have the same bits as animal cells, plus a few extras.
      • They have rigid cell wall made of cellulose which supports the cell and strengthens it.
      • Permanent Vacuole - contains cell sap, a weak solution of sugar and salts.
      • Chloroplasts - these are where photosynthesis occurs, which makes food for the plant. They contain a green substance called chlorophyll.
    • Bacteria Cells
      • Bacteria cells do not have a nucleus.
      • They are single-celled microorganisms.
      • A bacterial cell has cytoplasm and a cell membrane surrounded by a cell wall.
      • The genetic material floats in the cytoplasm because bacterial cells don't have a nucleus.
    • Yeast Cells
      • Yeast is a single-celled organism.
      • Yeast is a microorganism.
      • A yeast cell has a nucleus, cytoplasm, and a cell membrane, surrounded by a cell wall.
    • Specialised Cells
      • Palisade leaf cells are adapted for photosynthesis
        • They're packed with chloroplasts
        • Their tall structure means they have a big surface area for absorbing CO2.
        • Their thin structure means that you can fit lots of them in the top of a leaf.
      • Guard Cells are adapted for gas exchange and controlling water loss
        • Are a special Kidney shape which opens and closes the stomata in a leaf.
        • When the plant has lots of water, the guard cells fill with it and go plump. This makes the stomata open so gasses can be exchanged for photosynthesis.
        • Thin outer walls and thickened inner walls make the opening and closing work.
        • They're sensitive to light and close at night to save water.
      • Red Blood Cells are adapted to carry oxygen
        • Their concaved shape gives a big surface area for absorbing oxygen.
          • It also helps them to pass smoothly through capillaries to reach body cells.
        • They're packed with haemoglobin - the pigment that absorbs the oxygen.
        • They haven't got a nucleus to save more room for haemoglobin.
      • Sperm and egg cells are specialised for reproduction.
        • The main functions of an egg cell are to carry to female DNA and to nourish the developing embryo in the early stages.
        • When a sperm fuses with the egg, the eggs membrane instantly changes its structure to stop any more sperm getting in.
          • This makes sure the offspring ends up with the right amount of DNA.
        • The function of a sperm cell is to get the male DNA to the female DNA.
        • The sperm has a long tail and a streamlined head to help it swim to the egg. There are a lot of mitochondria in the cell to provide the energy needed.
        • The sperm also carry enzymes in their heads to digest through the egg cell membrane.


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