Chemistry of Life

1. Chemistry of Life Topic 3

2. Chemical Elements and Water 3.1

3. 3.1.1 The most frequently occurring chemical elements in living things are Carbon, Hydrogen, Oxygen and Nitrogen - found in all carbohydrates, proteins, lipids, and nucleic acids

4. 3.1.2 A variety of other elements are needed by living organisms but are less common, including: ·Sulfur ·Calcium ·Phosphorus ·Iron ·Sodium ·Potassium

5. 3.1.3

6. 3.1.3

7. 3.1.4 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. 3.1.4

9. 3.1.4 H O Hydrogen Bond Formation H H O H

10. 3.1.4 ·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

11. 3.1.5 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

12. 3.1.5 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

13. 3.1.5 ·This is also why water provides such a great living environment for many organisms

14. 3.1.5 Thermal continued: 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. 3.1.5 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)

16. 3.1.6 Functions of water in living organisms 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 (See Thermal Properties)

17. 3.1.6 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. 3.1.6 Metabolic Medium ·Being a good solvent for biochemicals means water is also a good medium for biochemical reactions

19. 3.1.6 Ecological effects ·high specific heat capacity of water allows it to maintain stable temperatures, excellent living environment for many organisms ·moderates the environmental temperature Large Specific Heat and Environmental Temperature

20. 3.1.6 Functions of water in living organisms 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 (See Thermal Properties)

21. 3.1.6 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

22. 3.1.6 Metabolic Medium ·Being a good solvent for biochemicals means water is also a good medium for biochemical reactions

23. 3.1.6 Ecological effects ·high specific heat capacity of water allows it to maintain stable temperatures, excellent living environment for many organisms ·moderates the environmental temperature Homework: Read "Water is Essential for Life" section of Textbook p 34-36 Add some info to notes

24. Homework: Read "Water is Essential for Life" Textbook p 34-36 Add some info to notes

25. 3.1 Review Teacher Notes to Self ·Model water molecule structure with arms. ·walk around and model H-bonding in liquid, heat up and cool off ·show solvent properties by having a few students be ions and the rest be water molecules. Review of Properties of Water: structure, H bond, solvent, ice, specific heat