biological membranes

• Endocytosis

  The process by which cells engulf materials from the external environment by forming vesicles from the plasma membranes and bringing them into the cell

  
  

  Allows the cell to take in nutrients, signalling molecules, and other substances from the external environment

  
  

  three main types: phagocytosis (cell eating), pinocytosis (cell drinking), and receptor-mediated endocytosis
• Exocytosis

  The process by which cells expel materials from vesicles that fuse with the plasma membrane, releasing their contents outside the cell

  
  

  Used to secrete molecules such as hormones, enzymes, neurotransmitters, and waste products

  
  

  Involved in processes such as neurotransmitter release at synapses, hormone secretion from endocrine cells, and the export of proteins from cells