1. Chapter 2: Chemistry of Life

2. Living Things Consist of Atoms of Different Elements
An atom is the smallest basic unit of matter.
Are made up of:
Protons
Found in the center of the atom
Have a mass of 1 AMU
Have a charge of positive 1
Neutrons
Have no charge (neutral)
Electrons
Found in orbits surround the protons & neutrons
Mass is 1/1837 AMU so we count it as 0
Have a charge of negative 1

3. An element is one particular type of atom, and it cannot be broken down into a simpler substance by ordinary chemical means
Carbon (C), Sodium (Na), Sulfur (S),…
Oxygen (O2), Hydrogen (H2), ...
Differ in the number of protons they have. This is their Atomic Number and no two elements have the same Atomic number
The number of protons (which equals the number of electrons), gives the element its physical and chemical properties

5. Elements on the Periodic Table
Atomic Number: # of protons = # of electrons 6 protons and 6 electrons Atomic mass: # of protons + # of neutrons 6 protons + 6 neutrons = 12 Element name Carbon Element symbol C

6. Elements in the Human Body
Symbol
Atomic Number (# of Protons = # of Electrons)
Atomic Mass
(# of Protons + # of Neutrons)
Carbon  C  6
12 
Hydrogen H  1 
Oxygen O  8 
16 
Nitrogen N  7 14
Phosphorus P  15 31
Sulfur S 16 32
Sodium Na 11 23
Chlorine Cl 17 35
Potassium K 19 39
Calcium Ca 20 40

7. Bohr Model of an Atom First orbital gets a maximum of 2 electrons
The next two get 8 electrons
Protons and Neutrons go in the middle
P = 6
E = 6
N = 6

8. Do Oxygen (16O8), Hydrogen (1H1), and then Nitrogen (14N7),

9. Let’s Combine Atoms together
Compounds are substances made up of atoms of different elements bonded together in a certain ratio.
H2O
CO2
NaCl
CH4
C6H12O6
Compounds have different properties than the elements that make it up. Sodium + Chlorine = Sodium Chloride (Salt)

10. Bohr Model of Sodium Chloride
Na+Cl-

11. Ionic Bonding
Ionic bonding occurs when electrons are transferred from the outermost energy levels of two atoms
Form ions – Atoms that have gained or lost electrons and now have a charge instead of being neutral
The number of protons no longer equals the number of electrons
Li+Cl-

13. Still with Ionic Bonding
Elements in Column 1A will easily bond ionically with elements in Column 7A.
The Column 1A elements will donate an electron and therefore have an extra positive charge and become a positive 1 ion
The Column 7A elements will gain an electron and therefore have an extra negatively charged electron and become a negative1 ion
What about Column 2A. Which column will it easily bond ionically with?
Column 6A and form either a +2 ion or a -2 ion.

14. 4 Covalent bonds are present in Methane.
Covalent Bonding
Let’s make Methane (CH4)
C has 6 electrons
2 in the first energy level
4 in the second
H has 1 electron only in its only energy level
Will it bond ionically or covalent with Hydrogen?
A Covalent bond forms when atoms share a pair of electrons
4 Covalent bonds are present in Methane.

15. Now let’s make a molecule of H2O and then CO2

16. Strength of Bonds
Covalent bonds are the strongest bonds making up the compounds found in living organism
Need a lot of energy to break the bond
Or pressure
Or chemicals called enzymes
Double and triple bonds are even stronger

17. Life Depends on the Hydrogen Bonds in Water
Properties of water:
Water is less dense as a solid
Ice floats and covers the water’s surface
Ice acts as an insulator and does not let the water below freeze or the organisms in the water
Water is a polar molecule
The oxygen end has a slightly negative charge
The hydrogen ends have a slightly positive charge

18. Hydrogen Bonds
Due to water’s polarity, the opposite charges of another water molecule can interact to form hydrogen bonds
Hydrogen bonds are attractive forces between a slightly positive atoms and a slightly negative atom
These bonds are weak bonds but when you add them all up, they are strong
Found holding water molecules together
Found between the two sides of a DNA molecule

19. Properties of Water due to Hydrogen Bonds
High Specific Heat:
The amount of heat needed to raise the temperature of a substance 1`C
Since water has so many hydrogen bonds, it takes a lot of energy to break the bonds to raise its temperature
Once it has absorbed the heat, it takes a lot of energy and time to lower the temperature
Why a watched pot never seems to boil!!
Why it takes a long time in the summer for the ocean or lakes to heat up.
Why water stays warmer in the fall
Why it takes a while for our body temperature to lower

20. Cohesion Like molecules being attracted to each other.
There is an attractive force holding adjacent water molecules together called hydrogen bonds
Water beading up on leaves or your window
Surface tension allowing the water strider to “walk on water”

21. Adhesion The attractive force between unlike molecules
Water molecules stick to other molecules IF they are also polar
Water molecules sticking to glass or a web
Water molecules sticking to roots
The meniscus in a graduated cylinder
How water molecules (or our blood since its basically water) can easily be transported through our capillaries (really thin blood vessels)

23. Water as the Universal Solvent
Water makes up about 70% of the mass of living things. For us, its closer to 60%. In order for chemical processes to occur, molecules and ions need to be able to dissolve or go into solution with water. Sugars, oxygen, Vit B & C, minerals such as salt, … Polar compounds or ionic compounds can go into solution with water Non-polar molecules like lipids (fats and oils), fat soluble vitamins like A, D, E, & K can’t. Oil and water do not mix!! They can only dissolve in other nonpolar solvents

24. Solutions
Solutions are a mixture of substances that is the same throughout (Homo gen eous)
Solvent is the substance that is present in the greatest amount that dissolves the solute
Water
Blood – 95% water
Solute is the substance going into solution in the solvent. It is being dissolved
Salt
Glucose

25. Ionic Compounds in Water
When ionically formed compounds go into solution with water, their ions dissociate or separate from one another
They remain as ions but are attracted to the opposite poles on the polar water molecules
Na+Cl- when placed in water, will break into:
Na+ ions which will surround the large Oxygen atom
Cl- ions which will cluster around the small hydrogen atoms

26. To reform the ionic bonds, just remove the water by evaporation!!

27. Acids and Bases
Acids are compounds that when placed in water, release a proton or Hydrogen ion (H+) into the water.
HCl, H2SO4, Citric Acid
Sour tasting
Corrosive

28. Bases or alkaline compounds remove H+ ions when in solution and have an excess of OH- ions (hydroxide ions)
Ammonia, Bleach, Blood, Bile, Soap…
Bitter tasting
Slimy to touch

29. Measuring pH or the Acidic or Alkalinity
pH or percent H+ ion concentration measures the amount of H+ ions in a solution

30. Every step on the pH scale is a 10X increase or decrease in H+ concentration.
Pure water has a pH of 7 and therefore, the H+ and OH- concentrations are equal

31. Buffers
Our body’s pH overall is about We can not withstand huge shifts in pH.
Buffers are chemicals which regulate the pH of the body, preventing sharp changes in pH