BIOCHEMISTRY - Textbook - Ostapchenko L. I. - 2012

Chapter 2. THE ROLE OF WATER, MACRO- AND MICROELEMENTS IN THE VITAL ACTIVITY OF ORGANISMS

An Organism can survive for weeks without food; however, in the absence of Water, life can be sustained for only a few days. Water performs numerous Functions in the organism. It serves as a solvent that ensures the realization of complex chemical, physicochemical, and biochemical reactions of cellular METABOLISM. As a component of Blood, water plays a vital role as a carrier of oxygen and nutrients to Tissues, as well as in the removal of CO₂ and metabolites from them. Blood also transports Antibodies and white Blood Cells that protect the body against infection. Water participates in body Temperature regulation in several ways. Blood carries heat away from active Organs, preventing a rise in their temperature. Heat can be transferred through the Skin to the environment by redirecting a portion of the blood to superficial Veins. Heat loss is further enhanced by the evaporation of water from the skin surface.

Water is also an indispensable component in Digestion processes. Digestion occurs via Hydrolysis, which is The breakdown of food components involving water. Digestive Enzymes are secreted in a dissolved form, ensuring their complete distribution within the chyme. An aqueous environment is also necessary for The excretion of toxic metabolites through the Kidneys and with feces.

It is generally considered that water constitutes about 70-75% of the total body mass. However, the actual percentage of water depends on the species of the organism and its age. For instance, E. coli and rat hepatocytes contain 69-70% water, pig embryos and jellyfish contain 97-98%, an adult pig's body contains only 40%, Cell/35.html">Mitochondria contain 70%, the myelin sheath contains ~20%, and Viruses contain no free water at all. In an adult organism, half of the water mass is intracellular. Extracellular wa

ter, as part of extracellular fluids, accounts for approximately 20-25% of body mass and is distributed among subcompartments: interstitial fluid accounts for ~17-18% of body mass, Blood Plasma accounts for 5%, and CEREBROSPINAL FLUID, synovial fluid, and Lymph account for up to 2-3%. Water is continuously exchanged between intracellular and extracellular fluids within the organism. At the same time, electrolyte concentration gradients are maintained by The Plasma Membrane.

Thus, water acts as a solvent, a product and substrate of Energy Metabolism, a participant in major biochemical transformations, alters molecular conformation and ion Hydration, and takes part in the regulatory and self-regulatory processes of cells, tissues, organs, and the organism as a whole.