1. New Quarter – New Unit!  Biochemistry Think back.
How do elements connect?

2. Chemical elements & water

3. Elements, atoms, & molecules
Living organisms are made of 25 chemical elements
Elements are the basic chemical units that cannot be broken apart by typical chemical processes
There are 92 naturally occurring elements
25 are required by living organisms
4 make up 96.3 of the human body

5. Chemical elements in living things
96% of most living things are made up of oxygen, carbon, hydrogen and nitrogen.
-These constitute the main ingredients of proteins, sugars and fats.
4% is made up of elements including calcium, phosphorus, iron, sulfur and sodium.

6. Why do we need them? Calcium = bone formation
Iron = transportation of oxygen in blood
Phosphorus = nerve transmission
Sulfur = helps in blood clotting
Sodium = muscle contraction
More info

7. Trace Elements
Essential in minute quantities for proper biological functioning (common additive in food and water)
Example: Iodine is a trace element that prevents goiter.
Many foods are fortified with trace elements and vitamins (which consist of two or more elements)

8. Goitre
Lacking iodine so the body cannot make thyroxin –a hormone made by the thyroid gland and used for metabolism… individuals tend to be overweight with this condition.
Found in iodized salt and seafood

9. Water, the great polar molecule!

10. Covalent Bonds Nonpolar covalent - atoms share electrons equally
Polar covalent - atoms share electrons unequally
One part of the molecule is slightly positive, and one part is slightly negative

11. In other words, if there is an atom that DOES NOT SHARE the electrons fairly, that atom acts like it has a negative charge!

12. 2.2.U1 Water molecules are polar and hydrogen bonds form between them.
Water molecules and their bonds
Water (H2O) is made up of two hydrogen atoms covalently bound to an oxygen atom
Share electrons unevenly
Leads to polarization
Slight Charges attract opposites.
Water molecules can associate via weak hydrogen bonds
Hydrogen bonds are transitory in nature – they constantly form, break and re-form

13. Hydrogen bonds are weak bonds between two polar molecules
The attraction between slightly positive regions and slightly negative regions creates hydrogen bonds
Hydrogen bonding occurs in many biologically important compounds
-Water
-DNA
-Proteins

14. Hydrogen bonds are an important part of the properties of water.
LE 2-10
Hydrogen bonds are an important part of the properties of water.
Hydrogen bond

15. Water is Cohesive it sticks to itself Note surface tension!

16. Water is Adhesive it sticks to other things
                                                  
Transpiration: water needs to stick to the tubes of the plant and to itself to release water into the air.

17. Water has a high specific heat: it takes a lot of energy to change the temperature of water
Energy is first used to break the hydrogen bonds, then to increase the temperature.

18. Hydrogen bonds in water moderate temperature
When water is heated, the heat energy is absorbed, disrupting hydrogen bonds
-The water stores a large amount of heat while warming only a few degrees
When water is cooled, heat energy is released as hydrogen bonds are formed
-The temperature of the water is lowered slowly

19. Water also
Water moderates temperature by evaporative cooling -The surface cools as the hottest molecules leave

20. Water expands when it freezes Ice floats… but cold water is dense and sinks, this causes a lake to ‘turnover’

21. Ice is less dense than liquid water
Hydrogen bonds in ice create a stable, three-dimensional structure
Ice is less dense than water, because it has fewer molecules in the same volume
Hydrogen bonds are stable
Hydrogen bonds
constantly break and re-form

22. Water is the solvent of life
A solution is a homogeneous mixture of a liquid solvent and one or more dissolved solutes
Because water is a polar molecule, it readily forms solutions with many other polar and ionic compounds
A solution in which water is the solvent is an aqueous solution

23. LE 2-14
Ion in
solution
Salt
crystal

24. Water as a solvent
Water separates Na+Cl- (salt) into sodium (Na+ ) and chlorine (Cl- )
Necessary biological functions i.e.
- Chlorine = carries electrical charge allowing nerve cells to work
- Sodium = provides for normal muscle contraction