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Discuss the Biological Importance of Water

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Introduction

Discuss the biological importance of water Water is a molecule with the formula H2O. There are two hydrogen atoms covalently bonded to one oxygen atom. The boiling point of water is 373 K and the melting point is 273 K, making water a liquid at room temperature. It is tasteless, colourless and odourless, yet many substances can dissolve in water meaning it has some important roles. It is essential for the proper functioning of the human body, plant life and the environment. Water is essential for the life processes in animals to take place effectively. The human body is made up of 75% water, containing 42 litres on average. Water is excreted through sweat, urine, faeces and water vapour in breath. Sweating is an important duty that every human body carries out. Water is released onto the skin which evaporates using the thermal energy of the body. The water can gain this energy easily and evaporate, cooling the body down and helping maintain a constant body temperature. ...read more.

Middle

Oxygen and carbon dioxide can dissolve in water, which provides sea creatures with oxygen to respire and live in deep oceans. The water is also transparent meaning that the suns rays can reach aquatic plants in the ocean enabling them to undergo photosynthesis. Water is essential in the digestion process. Enzymes are dissolved in water and produced in the mouth and stomach which break down the food and enable the nutrients to be used. The nutrients are absorbed from the villi in the small intestine into the blood stream where they are transported and used by the body. The blood the nutrients are transported is made up of 55% water. The blood plasma contains proteins, salts and other nutrients dissolved in the water. Many other substances also dissolve in the blood and are transported around the body to where they are needed, for example oxygen and carbon dioxide. Oxygen is dissolved into the blood from the alveoli in the lungs. ...read more.

Conclusion

In plants, osmosis also enables the cells to remain turgid and for the plants to remain upright. Water is absorbed by the roots of plants and it travels up the xylem to the leaves where it is used for photosynthesis to enable the plant to growth. The water can be absorbed readily by the roots as they have a large surface area. Water has great surface tension, due to the hydrogen bonds, enabling it to travel up the stem of the plant in the xylem vessels. The water evaporates from the leaves stomata, and as it does so more water is pulled up the xylem and up into the roots due to the surface tension. The hydrogen bonds between the water molecules hold the molecules together and provide the surface tension, allowing pond skaters to survive. Overall, water has very unique properties which make it ideal for the uses of it. No other molecule could be designed, which would improve water, as it is perfect for this world. ?? ?? ?? ?? Joelle Pike ...read more.

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**

The material covered in this essay is generally well written, although slightly confused in places, but there are some big omissions that need including in order to score a higher mark. Because the introduction is so long, and there is a large paragraph about cystic fibrosis the essay seems long enough, but actually when these parts are removed the main bulk of the essay is quite brief.

Student needs to cover:

- Latent heat of vaporisation
- Specific heat capacity
- Structural (e.g. maintaining pressure in the eye / turgor in plant cells)

Marked by teacher Rebecca Lewis 24/09/2012

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