1. Chemistry of Life
Topic 3

2. The most frequently occurring chemical elements in living things are Carbon, Hydrogen, Oxygen and Nitrogen
- found in all carbohydrates,
proteins, lipids,
and nucleic acids

3. A variety of other elements are needed by living organisms but are less common, including:
·Sulfur
·Calcium
·Phosphorus
·Iron
·Sodium
·Potassium

4. Element
Example role in plants
Example role in animals
Example role in prokaryotes
Sulfur
in some amino acids
Calcium
co-factor in some enzymes
co-factor in some enzymes & component of bones
Phosphorous
phosphate groups in ATP
Iron
in cytochromes
in cytochromes & haemoglobin
Sodium
in membrane function
in membrane function & sending nerve impulses

5. H2O

6. POLARITY – Polar Bear!!!

7. ·The H - O bond in water is a polar covalent bond.
Structure of water
·The H - O bond in water is a polar covalent bond.
·The nuclei of oxygen is significantly larger and has a greater charge than the nuclei of hydrogen
·Consequently the electron pair in the covalent bond is found ‘closer’ to the oxygen than the hydrogen nuclei
·This creates a polar molecule in which oxygen carries a small negative dipole and hydrogen carries a small positive dipole

8. Hydrogen Bond Formation
·Because of the partial charges, Oxygen atoms of each molecule are attracted to the hydrogen atoms of other molecules
·H-bonds are key to many of water's properties
·H-bonds are essential for many biological molecules to form, nucleic acids being the most important O H O H O H O H

9. Properties of Water
Cohesive: water molecules tend to attract each other and stick together
Causes water to have a high surface tension
- forms droplets
- vascular tissue in plants can draw water up to great heights against gravity
- helpful to organisms such as water bugs who walk on water
·Causes many of water's thermal properties

10. Thermal: water has a high specific heat capacity (or simply specific heat)
·Heat capacity is defined by the amount of energy needed cause a rise in temperature
·Water can absorb or release a lot of heat before changing temperature
·It takes energy to break the H bonds and get water molecules to increase in kinetic energy
·e.g. the water in blood keeps your body temperature fairly stable

12. ·This is also why water provides such a great living environment for many organisms
Ocean temperatures only fluctuate by +/- 1.5 degrees throughout the year.

13. Coolant
·Heat generated by the metabolic process of the body must be removed in order to prevent enzyme denaturation
·Water in the blood helps to carry this heat to your skin where it can be transferred to the air
·Sweat also helps to carry heat away from your body

14. Water also has a high heat of vaporization
·Because it takes a lot of energy (heat) to get water to change state, evaporating water takes a lot of heat with it.
·e.g. sweating: heat from the body causes sweat to evaporate, which removes heat and cools the body.

15. Ecological effects
·high specific heat capacity of water allows it to maintain stable temperatures, excellent living environment for many organisms
·moderates the environmental temperature

16. Solvent: The polarity of water gives it strong solvent properties for polar or ionic solutes
·Majority of molecules found in and around cells are polar or ionic: carbohydrates, protein, nucleic acids (DNA, RNA)
·"Like dissolves like"
·The polar water molecules are attracted to the charges in the solute (e.g. sodium)

17. Transport Medium ·Blood is mostly water
- Transports blood cells and dissolved molecules
-Common solutes in blood: glucose (blood sugar) amino acids, fibrinogen (protein for blood clotting), hydrogencarbonate ions (a means of transporting CO2)
Vascular tissue in plants
- Xylem carries water and dissolved minerals up from roots
- Phloem carries dissolved sugars down from leaves

18. Metabolic Medium
·Being a good solvent for biochemicals means water is also a good medium for biochemical reactions
Aqueous Solution
Location
Common Reactions
cytoplasm
fluid inside cell but outside organelles
glycolysis / protein synthesis reactions
nucleoplasm
fluid inside nuclear membrane
DNA replication / transcription
stroma
fluid inside chloroplast membrane
light-independent reactions of photosynthesis
blood plasma
fluid in arteries, veins and capillaries
loading and unloading of respiratory gases / clotting