Biology Question #657

aparna, a 16 year old female from Petaluma asks on February 13, 2002,

Why is blood salty?

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The answer

Barry Shell answered on February 13, 2002

Human's and all other animals evolved from creatures that originally came from the sea. In fact every living thing originally evolved from bacteria and very primitive organisms that began in the sea. In that environment, all life-sustaining enzymes evolved over millions of years to work in an environment that was essentially sea water. That is why the concentration of salt in the blood, and the pH of blood are virtually identical to sea water. The chemical pathways, and biological systems that sustain life evolved over millions of years in primitive bacteria and other single cell organisms and all these basic systems are preserved in all higher animals right up to human beings. So this is why blood is salty. In a sense we humans are bags of ocean water, because the ocean is where life began, and we have to carry the ocean around within us to live.

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