• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The Biological Importance of Water

Extracts from this document...

Introduction

´╗┐The Biological Importance of Water Water is by far one of the most important substances found on earth; it is vital for living organisms to survive and its structure plays a critical role in this. The most important factor in the structure of a water molecule is its polarity. This occurs because the oxygen atom is larger and therefore of a higher electronegativity (3.44) than hydrogen atoms (2.2). The electronegativity or tendency to pull electrons closer towards itself, determines the polarity of an atom or molecule. For example, a water molecule consists of one oxygen atom and two hydrogen atoms. The high electronegativity of the oxygen atom gives it a slight negative charge (shown by ?-) while the relatively low electronegativity and the consequent drawing away of electrons gives the hydrogen atoms a slight positive charge (shown by ?+). This means that each individual water molecule is dipolar, it has two separate and opposite charges within the same molecule. This is important because it allows a weak ?hydrogen bond? to be formed between water molecules, making it a generally cohesive substance. We can observe these electrostatic attractions when rainwater is beaded up on a leaf. It has formed droplets of many water molecules ?stuck? to each other through hydrogen bonding. ...read more.

Middle

to prevent from spilling. In the opposite fashion, when a narrow container such as a test tube is filled with water, a meniscus will be formed at the surface creating a curved edge of water. More useful examples of water?s surface tension include several species of insect and even reptile being able to effectively walk on water creating a whole new ecosystem on the surface of water masses such as ponds. Similarly, the cohesion of water molecules pulling together creates ?capillary action?. Capillary action or capillarity is when a small amount of water is pulled up through a narrow space, even though this sometimes means counteracting the force of gravity as in the example of a pipette or straw. This occurs because the adhesion forces between the water and glass molecules attract the first water molecules to the sides of the tube. The cohesive forces between the water molecules then attract more water upwards and this process continues until the gravitational force is too strong. Because of this property, water can travel along very narrow veins in roots and leaves much more easily than if it did not exist. Also largely due to the hydrogen bonds in water, it has a relatively high boiling point and specific heat capacity. ...read more.

Conclusion

In addition, if all the ice caps in the North Pole were to sink, the amount of water that would be displaced would entirely engulf all land. Another important feature of the water molecule is that it?s an amphiprotic molecule meaning that it can both accept protons and be a proton donor. Therefore, in any amount of pure water or aqueous solution, water molecules can rearrange themselves by losing a hydrogen nucleus to form a hydroxide ion (OH-) and a free proton (H+), of which the proton will then react with another water molecule to form hydronium (H3O). In other words, the dynamic equilibrium equation for the autoionization of water is: 2H2O ?? H3O+ + OH-. This characteristic makes water a good regulator of pH which is especially useful in cells alongside ongoing reactions. Importantly, water is also transparent so living organisms are able to see through it. This is another factor making marine ecosystems possible and it also allows vision through the tears (saline solution) in our eyes. Conclusively, the properties of water, due in large to its molecular structure, is what makes it possible for any form of life to survive. It sustains living organisms and balances systems both to create a suitable environment for life and with the organisms themselves, regulating specific variables like pH, temperature and, obviously, water content. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Molecules & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Here's what a teacher thought of this essay

4 star(s)

****

The opening of this essay is exceptional, and there are some really good points throughout. The student provides a fantastic level of detail, and shows he has done some extra reading beyond the syllabus.

Unfortunately later parts of the essay are a little less clear (the sections on specific heat capacity, and latent heat of vaporisation could be better written) and spends too long discussing the surface tension / cohesion properties conferred by hydrogen bonding.

It would also be nice to have a little bit about water's role within metabolism (in hydrolysis) and its supporting roles (e.g. as hydroskeletons).

Marked by teacher Rebecca Lewis 24/09/2012

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Molecules & Cells essays

  1. Marked by a teacher

    The Effect Of Temperature on the Respiration Of Yeast.

    5 star(s)

    against Temperature: - I predict that this graph will rise and at every 10oC the rate of reaction will double making the graph steeper until it shows a sign of reaching the optimum temperature. Average Time against Temperature: - I predict that this graph will drop because the time taken

  2. Investigating the effect of temperature on the activity of free and immobilised enzymes.

    * I felt that the Diabur strips used to measure the % of glucose allowed a lot of room for error. The lowest percentage they would measure was 0.1% and after 1% they only went up in 1% differences. As they had to left for two minutes before a reading

  1. DETERMINING THE WATER POTENTIAL OF A POTATO TUBER CELLS USING THE WEIGHING METHOD.

    There is no mechanism in plants to prevent excess water loss in the same way as excess water gain, but plasmolysis can be reversed if the cell is placed in a weaker solution. The equivalent process in animal cells is called crenation.

  2. An experiment to find of the isotonic point of root vegetables cells in contents ...

    of high concentration to a region of low concentration through a partially permeable membrane. The isotonic point is the point in which equilibrium exists in osmosis and is the point where the outward movement of water molecules of the cell equal the movement of water molecules into the cell.

  1. To find out how different concentrations of sucrose solution affect the incipient plasmolysis of ...

    A hypertonic solution should exist at 0.6M. Furthermore at 0.7M I predict the greatest decrease in length and mass because more solute molecules are present and less water molecules which means the net movement of water molecules will be out the root vegetables and into the hypertonic solution this should

  2. Investigation of the effect of adding different concentrations of NaCl to an enzyme-substrate (amylase-starch) ...

    Factors, which affect the action of enzymes, include: 1. Temperature - enzymes are inactive at temperatures lower than the optimum, and denatured at temperatures above the optimum temperature. 2. PH - enzymes are denatured at extremes of pH, and all enzymes have an individual optimum pH. 3. Substrate concentration - activity of enzymes increases with increasing substrate to a

  1. Biological Molecules

    This structure forms part of a DNA strand, which consists of two ? helix chains coiled together in parallel. These secondary structures may be further folded to form tertiary and quaternary structures which are 3 dimensional globular proteins, e.g. enzymes and haemoglobin.

  2. Describe the similarities and differences between plant and animal cells.

    Where the membranes lack ribosomes they are called smooth endoplasmic reticulm. The smooth ER makes lipids and steroids (e.g. cholesterol and reproductive hormones). Overall, the functions of the ER are as follows: * Provides a large surface area for chemical reactions.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work