The Biological Importance of Water
The Biological Importance of Water for Living Organisms Water is made up of two elements, 2 positively charged hydrogen molecules and one negatively charged oxygen molecule. Water molecules have uneven charge distribution as one end of the molecule is slightly positive and the other slightly negative, this is called polar. Ionic substances such as sodium chloride dissolve easily in water because the positively and negatively charged ions are separated due to the dipole nature of water. As water is dipolar, the positively charged atoms of one water molecule attracted the negatively charged molecule of another water molecule.
This is called hydrogen bonding. The hydrogen bonding between each molecule results in water being liquid at room temperature as it takes a lot of energy to turn it into gas due to its high heat capacity. Hydrogen bonding makes water extremely cohesive. Cohesion is the attraction between molecules of the same type (e. g two water molecules). Water is very cohesive due to the dipolar nature of the molecule. Cohesion helps the water to flow which is important in its transportation and enables substances to be easily dissolved and transported.
Waters dipole nature also makes it a good solvent. A lot of substances which take part in biological reactions are ionic, which means they are either made of one positively charged atom or molecule, or one negatively charged atom or molecule. As water is dipole, it means that the positively charged hydrogens will be attracted to the negative atoms or molecules, and the negatively charged oxygen will be attracted to the positively charged atoms or molecules, resulting in ions being totally surrounded by water molecules.
In other words, the atoms or molecules will be dissolved by the water. Water is important to living organisms because its molecules can move freely enabling chemical reactions to occur easily in solution. For example, seminal fluid is mostly water which enables fertilisation to occur easily and allows sperm to swim towards the egg. Hydrophilic substances (water loving substances) such as glucose and amino acids dissolve easily due to the nature of their polarity of their charged groups (OH for sugars, NH and COOH for amino acids). As hydrophilic ubstances such as glucose can dissolve in water, it is beneficial for plants as they take up minerals and substances in solution. Furthermore, oxygen is a component of water which also allows organisms to respire in water. Blood Plasma is the main component of blood. Plasma is made of 90% water which enables blood to carry its essential nutrients such as glucose and amino acids as well as respiratory gasses. As respiratory gasses are able to travel through blood plasma, it allows essential processes to take place such as respiration.
The plasma also carries other materials such as platelets which allow clotting, this is helped to be transported by the plasmas composition of 90% water. Waters high specific heat capacity allows it act as a buffer. This is essential in endothermic organisms that need to maintain a constant body temperature in order to optimise enzyme activity and regulate its metabolism. The large number of hydrogen bonding makes it difficult for the water molecules to evaporate. When water molecules do evaporate, an exothermic reaction takes place which acts as a cooling mechanism.
Water is able to remain a liquid over a large p of temperatures which is essential for metabolism and aquatic organisms. It is beneficial for aquatic organisms who are cold blooded as some may not be able to control their body temperature. It is beneficial as there is a minimal temperature fluctuation which keeps organisms body temperature constant. Keeping a constant temperature is important. In order for living organisms such as enzymes to keep functioning at their best, water needs to be kept a constant temperature to keep the enzymes working at their optimum temperature and stop them from denaturing.
Furthermore, water also provides internal support for many living organisms. For example, water fills up in the cells of plants to stop them going flaccid as apposed to their turgid structure. Keeping the cells turgid keeps the plant upright which also benefits the plant when it comes to catching as much light as possible when photosynthesising. Water can also be taken in through the xylem of a plant in a continuous column which is also a benefit for photosynthesis. In addition to that, water also provides internal support for mammals whose fetuses are surrounded in amniotic fluid.
This will not only provide protection for the fetus but also allow minerals to pass in and out of the fluid via osmosis. As well as internal support, water also provides external support. Water has a high surface tension which allows some organisms to stay afloat. An example of an organism which uses this to its advantage is a pond skater. They use the high surface tension to walk/glide along the waters surface, as there is a high tension, it prevents it from sinking. Furthermore, a high surface tension allows ice caps to stay afloat which provides insulation for aquatic organisms underneath.
Another reason for why ice caps stay afloat is that water is less dense when frozen. This means that the ice caps do not fall through into the water as it is less dense so it remains on the waters surface. Water is also essential for many chemical reactions such as photosynthesis and hydrolysis. In photosynthesis, water is transparent which allows light to penetrate through to the chlorophyll to absorb as much sunlight as it can. It also allows water to absorbed up the xylem in a constant column which also aids photosynthesis.
During hydrolysis, water breaks certain polymers which helps to break up salts when they are being dissolved. Water also provides lubrication to bones as it makes up synovial fluids in bone joints and the pleural fluid which surrounds the lungs. Lastly, water also has a significance in the food chain. Producers which are mainly made up of water such as lettuce and leaves are relied on to provide water for consumers. Water has a huge biological importance for all living organisms as it is the building blocks to each individual organism. Without water, there may not even be the life forms we see on this earth today.
