7. Transport in Cells

Transport Without Energy

Passive transport occurs when substances cross the plasma membrane without any input of energy from the cell. No energy is needed because the substances are moving from an area where they have a higher concentration to an area where they have a lower concentration. Water solutions are very important in biology. When water is mixed with other molecules this mixture is called a solution. Water is the solvent and the dissolved substance is the solute. A solution is characterized by the solute. For example, water and sugar would be characterized as a sugar solution. More the particles of a solute in a given volume, the higher the concentration. The particles of solute always move from an area where it is more concentrated to an area where it is less concentrated. It’s a little like a ball rolling down a hill. It goes by itself without any input of extra energy.

The different categories of cell transport are outlined in Figure Cell transport can be classified as follows:

  • Passive Transport which includes
    • Simple Diffusion
    • Osmosis
    • Facilitated Diffusion
  • Active Transport can involve either a pump or a vesicle
    • Pump Transport can be
      • primary
      • secondary
    • Vesicle Transport can involve
      • Exocytosis
      • Endocytosis which includes
        • Pinocytosis
        • Phagocytosis
        • Receptor-Mediated Endocytosis
Cell Transport
The Cell Transport Concept Map illustrates various types of cell transports that happen at the plasma membrane

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