Water also contributes to the formation of membranes surrounding cells. In the dehydrated cell, there is less water pushing outward so the cell becomes wrinkled. In the hydrated cell (left), the water pushes outward and the cell maintains a round shape. Figure 2:В Water impacts cell shape.В Water creates pressure inside the cell that helps it maintain shape. As shape is critical for biochemical processes, this is also one of waterвЂ™s most important roles. Water allows everything inside cells to have the right shape at the molecular level. However, even some plants, which can maintain their cell structure without water, still require water to survive. The water inside many cells (including those that make up the human body) creates pressure that opposes external forces, similar to putting air in a balloon.

Visually, water fills cells to help maintain shape and structure (Figure 2). Water also has an important structural role in biology. Thus, waterвЂ™s role as a solvent facilitates the transport of molecules like oxygen for respiration and has a major impact on the ability of drugs to reach their targets in the body. Water-based solutions like blood help carry molecules to the necessary locations. On a biological level, waterвЂ™s role as a solvent helps cells transport and use substances like oxygen or nutrients. WaterвЂ™s extensive capability to dissolve a variety of molecules has earned it the designation of вЂњuniversal solvent,вЂќ and it is this ability that makes water such an invaluable life-sustaining force. This is what happens when you put salt in water, because salt is composed of sodium and chloride ions. Water breaks apart these ionic molecules as well by interacting with both the positively and negatively charged particles. Similar to polarity, some molecules are made of ions, or oppositely charged particles. This is what happens when you put sugar crystals into water: both water and sugar are polar, allowing individual water molecules to surround individual sugar molecules, breaking apart the sugar and dissolving it. In the act of surrounding the polar molecules of another substance, water wriggles its way into all the nooks and crannies between molecules, effectively breaking it apart are dissolving it. ДЇurthermore, since most biological molecules have some electrical asymmetry, they too are polar and water molecules can form bonds with and surround both their positive and negative regions. Cohesion also contributes to waterвЂ™s high boiling point, which helps animals regulate body temperature. The cohesion of water molecules helps plants take up water at their roots. Importantly, this bonding makes water molecules stick together in a property called cohesion. In this case, the positive hydrogen of one water molecule will bond with the negative oxygen of the adjacent molecule, whose own hydrogens are attracted to the next oxygen, and so on (Figure 1). This attraction allows water to form relatively strong connections, called bonds, with other polar molecules around it, including other water molecules. This is because of the phenomenon wherein opposite charges attract one another: because each individual water molecule has both a negative portion and a positive portion, each side is attracted to molecules of the opposite charge. Water is the вЂњUniversal SolventвЂќДЄs a polar molecule, water interacts best with other polar molecules, such as itself. These atoms are of different sizes and charges, which creates the asymmetry in the molecular structure and leads to strong bonds between water and other polar molecules, including water itself. Water molecules are made of two hydrogens and one oxygen. This charge differential is called polarity and dictates how water interacts with other molecules.

When the hydrogens bind to the oxygen, it creates an asymmetrical molecule with positive charge on one side and negative charge on the other side (Figure 1). Water is a simple molecule composed of two small, positively charged hydrogen atoms and one large negatively charged oxygen atom.

Many of waterвЂ™s roles in supporting life are due to its molecular structure and a few special properties. Clearly water is vital for survival, but what makes it so necessary? The Molecular Make-up of Water This crucial dependence on water broadly governs all life forms. Likewise, a person could survive a month without food but wouldnвЂ™t survive 3 days without water. A loss of just 4% of total body water leads to dehydration, and a loss of 15% can be fatal.

Water makes up 60-75% of human body weight.

Another word for properties bio