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
Define Measuring cylinder - Nutritional Biochemistry? It is used for measuring those reagents which need not be added in very accurate volumes. Strong acids and alkalis are add

Bovine parainfluenza This virus belongs to the genus Respirovirus in the subfamily Paramyxovirinae of family Paramyxoviridae. It causes respiratory syndrome in cattle and shee

Associated nerves and vessels The Anterior superior alveolar, Infraorbital, and Posterior superior alveolar nerves and arteries provide both the innervation and blood supply to

Vitamin C (Ascorbic acid) Vitamin C, ascorbic acid is also called anti-scorbutic vitamin. Ascorbic acid occurs as white crystals or white crystalline powder without odour and o

Dietitians and nutritionists Dietitians and nutritionists, who are associated with hospitals and clinics generally have regular work hours. At times, they may be required to wo

What are the five human digestive secretions? Which of them is the only one that does not contain digestive enzymes? The human digestive secretions such as: saliva, gastric jui

What is genesis of coronary artery diseases ? Like any other disease conditions, origin of CAD depends on an interplay between the heredity and environment so called 'nature' a

Define Immediate and Longer term Adjustment to Altitude Hypoxia? Arterial hypoxia precipitates the immediate physiological adjustments to altitude and process of acclimatizatio

Summer Stratification - Thermal stratification Thermal stratification is fairly pronounced during the summer seasons in most lakes of the temperate (cold) regions but is rare

Explain the Naturally occurring Food Chemicals? Pharmacologically active substances include vasoactive amines such as histamine, tyramine, tryptamine, phenylethylamine, and ser