How is water important to all living things?

Question

How is water important to all living things?

Answer 1

Water has several properties that make it central to all living things.  Water molecules are held together by weak bonds called hydrogen bonds.  These bonds allow water to carry on several functions vital to life.  They are:

1. Cohesion: is the sticking together of similar molecules. Water is very cohesive. This allows water to be pulled along a pathway with relative ease.  An example would be our blood being pumped through our body and the cohesiveness of the cytoplasm in the cells.

2. Surface Tension: cohesion allows water to pull together and form droplets or form an interface between it and other surfaces. The measure of how hard it is to break this interface is its surface tension.  Water allows materials to rest upon it if the surface tension is not broken. Pollen, dust, water insects, and other biological materials are able to remain on the surface of the water because of this tension.

3. Adhesion: The sticking of one substance to another. Water is a good adhesive. It will cling on to many objects and act as a glue. Capillary Action is an example of cohesion and adhesion working together to move water up a thin tube such as the xylem tube of plants.

4. Imbibition: The process of soaking into a hydrophilic substance. Water being taken into a sponge, into a seed, into paper towels.

5. High Specific Heat: Specific heat of a substance is the heat needed (gained or lost) to change the temperature of 1g. of a substance 1degree Celsius. Heat is the total quantity of kinetic energy due to molecular motion. Temperature measures the intensity of the average kinetic energy of the molecules.Heat and temperature are not the same thing. A Kilocalorie or large C equals 1,000 small calories.It takes 1,000 calories to raise 1,000g. of water 1 degree C. Nutritional Packaging has the calorie measurements in Kilocalories. One gram of Protein = 3 calories. This means 3,000 small calories or 3 Kilocalories.

This high specific heat allows water to act as a heat sink. Water will retain its temperature after absorbing large amounts of heat, and retain its temperature after losing equally large amounts of heat. The reason for this is that Hydrogen bonds must absorb heat to break. They must release heat when they form. The Ocean acts as a tremendous heat sink to moderate the earth's temperature.

6. High Heat of Vaporization: Water must absorb a certain amount of additional heat to change from a liquid into a gas. This extra heat is called heat of vaporization. In humans, this value is 576 cal/g. This results in evaporative cooling of the surface.  That's why sweating occurs when our body over heats.

7. Freezing and Expansion of Water: Water is most dense at 4 degrees C. At ) degrees C. it is 10% less dense. Ice floats because maximum Hydrogen bonding occurs at 0 degrees C.  This protects fish and other life living in very cold areas of the world from freezing in their environment as the ice floats and insulated the rest of the water keeping it from freezing solid.

8. Versatile Solvent: Water is a major solvent in nature. When water and another substance is mixed the resulting solution is called an aqueous solution. Any solution contains the following parts:

Solute (what's being dissolved) + Solvent (what is doing the dissolving) = Solution.  Osmosis runs on the difference between the solvent and solute concentrations of the cells and their environments.

Answer 2

From a biological standpoint, water has many distinct properties that are critical for the proliferation of life that set it apart from other substances. It carries out this role by allowing organic compounds to react in ways that ultimately allow replication. All known forms of life depend on water. Water is vital both as a solvent in which many of the body's solutes dissolve and as an essential part of many metabolic processes within the body. Metabolism is the sum total of anabolism and catabolism. In anabolism, water is removed from molecules (through energy requiring enzymatic chemical reactions) in order to grow larger molecules (e.g. starches, triglycerides and proteins for storage of fuels and information). In catabolism, water is used to break bonds in order to generate smaller molecules (e.g. glucose, fatty acids and amino acids to be used for fuels for energy use or other purposes). Water is thus essential and central to these metabolic processes. Therefore, without water, these metabolic processes would cease to exist, leaving us to muse about what processes would be in its place, such as gas absorption, dust collection, etc.

Water is also central to photosynthesis and respiration. Photosynthetic cells use the sun's energy to split off water's hydrogen from oxygen. Hydrogen is combined with CO2 (absorbed from air or water) to form glucose and release oxygen. All living cells use such fuels and oxidize the hydrogen and carbon to capture the sun's energy and reform water and CO2 in the process (cellular respiration).

Water is also central to acid-base neutrality and enzyme function. An acid, a hydrogen ion (H+, that is, a proton) donor, can be neutralized by a base, a proton acceptor such as hydroxide ion (OH−) to form water. Water is considered to be neutral, with a pH (the negative log of the hydrogen ion concentration) of 7.