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Home > Biology > The body in action > The need for energy


The need for energy


Blood is a pale yellow liquid called plasma with red blood cells, white blood cells and platelets suspended in it.

  • plasma carries dissolved carbon dioxide and food
  • red blood cells collect oxygen in the lungs and carry it round the body
  • white blood cells fight infections
  • platelets help blood to clot where there has been a cut

Red blood cells contain a dark red chemical called haemoglobin [haemoglobin: the red protein found in red blood cells that transports oxygen round the body. Haemoglobin combines with oxygen in the lungs to form a bright red chemical called oxyhaemoglobin. When the blood gets to places where oxygen is being used up oxyhaemoglobin releases the oxygen and turns back into haemoglobin.


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