Water - properties and functions, Biology

WATER

Occurence

  1. Water is the most abundant substance, covering 70% of earth's surface.
  2. It constitutes 60-90% of living cells.

             5-6% in tooth enamal, 60 - 70% in human adults, 90-92% in brain cells, 90 - 95% in human embryo, 99% in Jelly                   Fish.

  1. 95% of the total water occurs in the free state.
  2. Only 5% is found in bound state.

PROPERTIES

  1. Water freezes at 0oC and boils at 100oC. It remains liquid in between the two temperatures.
  2. Water is colourless and transparent.
  3. Pure water does not have any odour or taste.
  4. All the essential mineral elements dissolve in water. Water is a medium for their availability to organisms.
  5. Water is a very poor conductor of electricity in the pure state. However, it is good conductor of electricity in the presence of ionised chemicals.
  6. Pure water is neutral with a pH of 7.
  7. Water is a small polar molecule having positive and negative charges.
  8. Water has a high dielectric constant which enables the oppositely charged ions of electrolytes to remain suspended in water.
  9. Surface Tension is very high.
  10. Water has the maximum specific heat.  Water has the maximum density at 4oC.

FUNCTIONS OF WATER

  1. Water is a major component of cells and body fluids.
  2. Water is a habitat of numerous animals, plants and other organisms.
  3. Water has the maximum solvent action for both electrolytes and nonelectrolyte polar substances.
  4. Water is also dispersion medium for hydrophilic or reversible colloids.
  5. Water is transport medium in both plants (xylem, phloem) and animals (blood and and lymph).
  6. Excretory products are eliminated mainly in solution form. It helps in homoeostasis.
  7. Water maintains the turgid state of cells and soft organs.
  8. In photosynthesis, water molecules undergo photolysis, evolve O , provide H+ ions and electrons for reduction of CO to organic state.
  9. Water present in tissue fluid, coelomic fluid, pericardial fluid, cerebrospinal fluid, etc. keeps the tissues moist for their optimum functioning. It is also a lubricant of joints.
  10. Seeds and spores require water for their germination.
  11. Cornea is protected from microbe infection and dust by lachrymal fluid. Mucus protects the nasal tract from the same. In both water is the main ingredient for flushing of teh particles.
  12. Heat spreads in water quite repidly due to high thermal conductivity. It distributes heat uniformly and prevents sudden changes in temperature.
  13. Shortage of water on land has been a major selection pressure in evolution of xerophytes, desert animals, seed plants, etc.
Posted Date: 10/9/2012 2:58:45 AM | Location : United States







Related Discussions:- Water - properties and functions, Assignment Help, Ask Question on Water - properties and functions, Get Answer, Expert's Help, Water - properties and functions Discussions

Write discussion on Water - properties and functions
Your posts are moderated
Related Questions
What is Carbohydrates? Carbohydrates : Carbohydrates function mainly as immediate sources of energy, stored energy such as starch, and structural components of cells. Carbohyd

Define the term - lamellac The inner membrane is folded into very closely packed membranes called the lamellac. The lamellae flatten out at regular intervals into structures c

Assume that you have 1 mL of a solution amylase (an enzyme) at a concentration of 15 mg protein/mL. Calculate the volume of diluting buffer that you would have to add to 1.0 mL of

The Father of Botany (370-285 B.C.); of all the men who ever lived upon the earth certainly one of the most remarkable was Theophrastus of Eresus who was born about 370 B.C. on the

Explain the Classification of simple proteins? 1) Albumins: Proteins such as egg albumin and serum albumin are soluble in water and coagulable by heat. 2) Globulins: These p

In an experiment, isolated chloroplast thylakoids were incubated at pH 4.0 with ADP and inorganic phosphate (Pi) added to the medium and then transferred to a medium having pH 8.0.

What is the name of the DNA duplication process? What is the main enzyme that participates in it? The process of copying, or duplication, of the DNA molecule is called replica

How to calculate the Net Protein Utilization (NPU)? Mitchell (1922) introduced the term 'Net Utilization of Dietary Protein' which is a product of digestibility coefficient and

Why do cells of the nephron tubules present a great amount of mitochondria? The cells of the tubule wall have high number of mitochondria because lots of substances are resorbe

Nerves - Organisation of Nervous System Due to the pattern of distribution of neurons as described above, there are bundles of nerve fibers, called nerves, connecting the cent