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IB Biology - Exocytosis and Endocytosis

Chapter 1.4 - Membrane Transport

May 3, 2020
  • The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis. Vesicles move materials within cells.

Endocytosis

  • in previous IB biology topics, we have mention large molecules can take up by the cell via a carrier protein 
  • however, to take up a very large and bulky molecule, it requires endocytosis 
  • The process of endocytosis: 
  1. the cell membrane moves inwards and surrounds the molecule
  2. the cell membrane encloses, the molecule is engulfed in a vesicle 
  3. the vesicle is detached from the membrane, moving into the cell 
  4. lysosomes move in the vesicle, digesting the molecules
  • White blood cell uses endocytosis to eliminate the bacteria from our body 

Exocytosis

  • Do you still remember the IB biology chapter 1.2? In the chapter, we mention that within the cell, proteins are produced in the ribosome in the rough ER, and are processed in the Golgi apparatus. After processing, the protein is released out from the cell by a secretory vesicle 
  • the cell releases molecules via exocytosis 
  • The process of exocytosis:
  1. The molecule from the Golgi apparatus is surrounded by vesicle (the vesicle is made by phospholipid)
  2. The vesicle move towards the cell membrane 
  3. The vesicle fuses with the cell membrane
  4. the molecule inside the vesicle is released out from the cell 
  • The endocytosis and exocytosis work together to balance the length of the cell membrane. The exocytosis remedies the cell membrane loss in the endocytosis while the endocytosis uses up the extra cell membrane from the exocytosis 
  • the cell membrane flexibility and fluidity enables the exocytosis and endocytosis to happen 
    e.g. the cell membrane moves inwards, the cell membrane extends when the vesicle fuses with it 

In the IB biology chapter, you have to understand:

  1. the process of endocytosis and exocytosis 
  2. how the cell membrane properties enable the endocytosis and exocytosis 

~That is the end of topic~

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