Water=Vital Living Organism =Water up to 80% of cells contents
Functions in and out of a cell:
· Water is a solvent (some substances dissolve in it) most biological reactions take place in solutions= Important
· Water transport substances. Can be transported more easily if dissolved in a solvent and liquid (water)- easily transport (glucose, oxygen) around plants and animal cells
Water Molecules have a simple structure:
1. A molecule of water (H20) is 1 atom of oxygen (O) joined to 2 atoms of hydrogen (H2) by shared electrons.
2. Shared negative hydrogen electrons are pulled towards the oxygen atom, other side of hydrogen ion left with a slight + charge.
Unshared negative electron on the oxygen atom gives it a slight negative charge
4. Makes a water dipolar molecule- it has a - charge on one side and a + charge on the other.
5. The - charged oxygen atoms of water attract the + charged hydrogen atoms of other water molecules.
6. This attraction is called Hydrogen Bonding.
Diagram of Water Molecule Structure: (handrawn)
Structure of water molecule—properties---function
Water’s Dipole Nature makes it very cohesive:
1. Cohesive=attraction molecules of the same type (e.g. 2 water molecules) very cohesive, stick together because there Dipolar
2. Helps water to flow= great for transporting substances
Water’s Dipole nature makes it a good Solvent:
1. A molecule is Dipolar if it have a – charged bit and a + charged bit.
2. Lots of important substances in bio reactions are ionic- one – charged ion and one + charged ion.
3. Water- the + end of water molecule will be attracted to the – ion.
4. The – end of the water molecule will be attracted to the +ion.
5. Meaning the ions will get completely surrounded by water molecules--- they are dissolved
6. Therefore water’s dipole nature makes it useful as a solvent for other polar molecules.
Positve ions dissolve in water.
Negative ions dissolve in water.