Magnesium (Mg)2+ ---> is a constituent of chlorophyll.
Iron (Fe)2+ ---> is a consituent of haemoglobin.
Phosphate (PO4)3- ---> constituent of DNA/RNA and phospholipids in the cell membrane.
Calcium (Ca)2+ ---> used by animals to form healthy bones and teeth.
WATER:
Water is a polar molecule and has no overall charge. The slightly -/+ regions are attracted to charged regions of other molecules, forming hydrogen bonds.
High specific heat capacity-
A lot of energy is needed to raise the temperature of water because the H-bonds restrict movement.
- The temperature of aquatic habitats is stable so the organisms don't experience extreme conditions.
- This also allows enzymes within the cell to work efficiently.
Density-
As the temperature of water decreases, the H-bonds are less able to break so they form a semi-crystalline structure of the molecules. This holds the molecules apart, which makes ice less dense than water.
- Ice insulates water beneath, allowing organisms to survive.
Cohesion-
Water has a high cohesion because of hydrogen bonding. Cohesion also gives water a high surface tension.
- Cohesion allows water to travel up the xylem.
- It also allows small organisms to walk on water, e.g. the pond skater.
Universal solvent-
Water is a good solvent because it is a polar molecule and will attract other charged particles. It also acts as a transport medium for dissolved substances.
- In animals, blood transports many dissolved substances.
- In plants, water transports dissolved mineral ions inside the xylem and dissolves sucrose/amino acids inside the phloem.
Water is metabolite-
It is used in biochemical reactions as a reactant.
- In photosynthesis water reacts with carbon dioxide to produce glucose.
- Hydrolysis reactions in the body. (maltose + water ---> glucose + galactose)
Transparency-
Water is transparent which allows light to pass through it.
- This allows aquatic plants to photosynthesise.
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