Only 25 of the 90 natural elements (periodic table) are essential for life. We call these biogenic elements.
They can be divided into two groups: macroelements (need lots) and microelements (needed in small quantities)
Macroelements
O - O2, H2O
C - CO2, organic compounds (lipids, carbohydrates, proteins, nucleic acids, vitamins)
H - H2O, CH4
N - amino acids, proteins, nucleic acids
H2O
-the most important inorganic compound
70-95% of most organisms (98% in jellyfish, about 70% in humans)
Image from www.brooklyn.cuny.edu/bc/ahp/SDgraphics/PSgraphics/SD.PS.LG.Water.html
- from the molecular structure you can see that water is a dipolar molecule with electron sharing
-hydrogen bond: attraction of opposite charges, weak bond, H end attracts O end of another H2O or an anion
-very important in holding large molecules together, eg. proteins, DNA, etc
Properties:
1. Excellent solvent - H2O attracts ions and surrounds them, split ionic bond (dissociation) and prevents reassociation by creating hydrate shells (vizburok) around them, therefore they dissolve. eg. NaCl. It also works for polar molecular substances eg. sucrose. H2O can't dissolve apolar substances
2.Thermal properties: High thermal capacity (fajhő) - this is the amount of heat needed to raise the temperature of 1g by 1 degree Celsius. Water has a high boiling point (liquid at ambient temperature and pressure)
3. Surface tension (force that causes surface to contract to occupy the least possible area): Highest of any liquid except mercury, therefore water is pulled into spherical shapes and it creates a surface film, which supports insects, creates a habitat and causes capillarity (cohesion and adhesion) in plants' xylem.
4. Freezing properties: At temperatures LESS than 4C, volume is high and density is low, therefore ice floats - this protects organisms that live in water. At 4C water is densest and collects at the bottom. Ice is a thermoinsulator.
Macroelements
O - O2, H2O
C - CO2, organic compounds (lipids, carbohydrates, proteins, nucleic acids, vitamins)
H - H2O, CH4
N - amino acids, proteins, nucleic acids
H2O
-the most important inorganic compound
70-95% of most organisms (98% in jellyfish, about 70% in humans)
- from the molecular structure you can see that water is a dipolar molecule with electron sharing
-hydrogen bond: attraction of opposite charges, weak bond, H end attracts O end of another H2O or an anion
-very important in holding large molecules together, eg. proteins, DNA, etc
Properties:
1. Excellent solvent - H2O attracts ions and surrounds them, split ionic bond (dissociation) and prevents reassociation by creating hydrate shells (vizburok) around them, therefore they dissolve. eg. NaCl. It also works for polar molecular substances eg. sucrose. H2O can't dissolve apolar substances
2.Thermal properties: High thermal capacity (fajhő) - this is the amount of heat needed to raise the temperature of 1g by 1 degree Celsius. Water has a high boiling point (liquid at ambient temperature and pressure)
3. Surface tension (force that causes surface to contract to occupy the least possible area): Highest of any liquid except mercury, therefore water is pulled into spherical shapes and it creates a surface film, which supports insects, creates a habitat and causes capillarity (cohesion and adhesion) in plants' xylem.
4. Freezing properties: At temperatures LESS than 4C, volume is high and density is low, therefore ice floats - this protects organisms that live in water. At 4C water is densest and collects at the bottom. Ice is a thermoinsulator.
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