1. The Chemistry of Life Domains of Study Domain of BioMolecules
Domain of Cells
Domain of Organisms
Domain of Populations
Domain of Communities

2. Why are we studying chemistry?
Chemistry is the foundation of Biology

3. What is an atom?
An atom is the smallest part of an element that keeps all the properties of the element.
CHNOPS: elements essential for life
Carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur
-Electron = Negative charge=SAME AS atomic number
-Proton = + charge=SAME AS atomic number
-Neutron (Neutally charged) = Mass-number

4. Life requires ~25 chemical elements
About 25 elements are essential for life
Four elements make up 96% of living matter:
• carbon (C) • hydrogen (H)
• oxygen (O) • nitrogen (N)
Four elements make up most of remaining 4%:
• phosphorus (P) • calcium (Ca)
• sulfur (S) • potassium (K)

5. Everything is made of matter Matter is made of atoms
Hydrogen
1 proton
1 electron
Oxygen
8 protons
8 neutrons
8 electrons
Proton +
Neutron
Electron –

6. What is an element?
-An element is made up of only one kind of atom. An element can’t be broken down into a simpler form by chemical reactions. Elements are arranged in a chart known as the periodic table. The table tells us it’s mass, how many protons it has, and its symbol.
Trace elements:  are those required by an organism in minute quantities.
-A compound is made up of two or more elements in exact proportions. There are two types of compounds ionic and molecular. Ionic compounds attract one to one another to form a neutral compound such as salt NaCl.

7. The World of Elements Different kinds of atoms = elements H C N O NaMg P S K Ca
Different kinds of atoms = elements

8. -What is a Molecule?
-A molecule is a group of atoms held together by the energy of chemical bonds.
-----Energy is the capacity to cause change.
-----Potential energy is the energy that matter has because of its location or structure. The electrons of an atom differ in their amounts of potential energy. An electron’s state of potential energy is called its energy level, or electron shell.

9. Part 2: How electrons form bonds -Bonding properties
Effect of electrons
electrons determine chemical behavior of atom
depends on number of electrons in atom’s outermost shell
valence shell
How does this atom behave?

10. Bonding properties Effect of electrons
What’s the magic number?
Bonding properties
Effect of electrons
chemical behavior of an atom depends on number of electrons in its valence shell
Sulfur on the LEFT
Magnesium on the RIGHT
How does this atom behave?
How does this atom behave?

11. Elements & their valence shells
Elements in the same row have the same number of shells
Moving from left to right, each element has a sequential addition of electrons (& protons)

12. Elements & their valence shells
Elements in the same column have the same valence & similar chemical properties
Remember
some food chains are built on reducing O to H2O
& some on
reducing S to H2S
Oxygen has medium electronegativity so doesn’t pull electrons all the way off hydrogen whereas chlorine would.
So oxygen forms a polar covalent bond.
Carbon has only a weak electronegativity so forms a nonpolar covalent bond

13. Chemical reactivity Atoms tend to
complete a partially filled valence shell or
empty a partially filled valence shell
This tendency drives chemical reactions…
and creates bonds – –

14. Bonds in Biology Weak bonds Strong bonds Hydrogen bond hydrogen bonds
H2O
Weak bonds
hydrogen bonds
attraction between + and –
hydrophobic & hydrophilic interactions
interaction with H2O
(ionic)
Strong bonds
covalent bonds
H2O
Covalent bond –
H2 (hydrogen gas)

15. Covalent bonds Why are covalent bonds strong bonds? Forms molecules
two atoms share a pair of electrons
both atoms holding onto the electrons
very stable
Forms molecules H
Oxygen – H O
H — H
H2 (hydrogen gas)
H2O (water)

16. Multiple covalent bonds
2 atoms can share >1 pair of electrons
double bonds
2 pairs of electrons
triple bonds
3 pairs of electrons
Very strong bonds
More is better! H
H–C–H –

17. Nonpolar covalent bond
Pair of electrons shared equally by 2 atoms
example: hydrocarbons = CxHx
methane (CH4 )
balanced, stable, good building block

18. Polar covalent bonds Pair of electrons shared unequally by 2 atoms
example: water = H2O
oxygen has stronger “attraction” for the electrons than hydrogen
oxygen has higher electronegativity
water is a polar molecule
+ vs – poles
leads to many interesting properties of water… H
Oxygen + – – – – +

19. Hydrogen bonding Polar water creates molecular attractions Weak bond
attraction between positive H in one H2O molecule to negative O in another H2O
also can occur wherever an -OH exists in a larger molecule
Weak bond H H O
APBio/TOPICS/Biochemistry/MoviesAP/03_02WaterStructure_A.swf
Let’s go to the videotape!

20. Reactions
Chemical reaction: process by which substances change into different substances through the breaking and forming of chemical bonds.
Reactant: substance that is changed by a chemical reaction.
Product: substance formed by a chemical reaction.
Equilibrium: condition in which reactants and products of a chemical reaction are formed at the same rate.
Exothermic: chemical reaction that yields a net release of energy in the form of heat.
Endothermic: chemical reaction that requires a net input of energy
2H2 + O H2O

21. -What is organic? What are some examples of organic compounds?
-Organic Molecule: A molecule made up a large carbon-based structure that is found in or produced by living organs (e.g. carbohydrates, lipids)
What are some examples of organic compounds?
-Macromolecule: A large molecule (polymer) composed of many smaller organic molecules called monomers. There are four types of biological macromolecules: proteins, carbohydrates, lipids, and amino acids.
Monomer: A molecule that can chemically react with other like molecules to form a larger molecule called a polymer.
Polymer: A large molecule composed of smaller units, called monomers, linked together by chemical bonds (e.g. proteins are polymers of amino acids).

22. Lipids: Large biomolecules that are made of mostly carbon and hydrogen with small amount of oxygen. Fats, oils, waxes, and steroids are all lipids.
Nucleic Acids: A complex biomolecule that stores cellular information in the form of a code. They are polymers made of smaller subunits called nucleotides. A nucleotide consists of a sugar deoxyribose, a phosphate group, and a nitrogenous base.
Proteins: A large complex polymer composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. They provide structure for tissues and organs and carry out cell metabolism.
-Enzyme: A protein that functions as a biological catalyst and accelerates the rate of a biochemical reaction by reducing the required activation energy of the reaction while remaining unchanged by the reaction.
Catalyst: A substance that accelerates the rate of a chemical reaction by decreasing the activation energy of the reaction without being changed by the reaction (enzymes).

23. Carbohydrates
-Carbohydrates: A biomolecule composed of carbon, hydrogen, and oxygen with a ratio of about two hydrogen atoms and one oxygen atom for every carbon atom. They are types of sugars.
-Monosaccharide: A monomer of a carbohydrate molecule, of known as a simple sugar like glucose or fructose, or ribose. C6H12O6
-Disaccharides: Two-sugar carbohydrate. Sucrose (table sugar) is a combination between glucose and fructose
-Polysaccharides: Composed of many monosaccharide’s subunits. Starch, glycogen, and cellulose are examples of polysaccharides. They serve as storage of energy for our cells.

24. Chemistry Terms
pH scale: A system of measurement ranging from one to fourteen that indicates the relative concentration of hydrogen ions in a solution. A pH of one indicates a strong acid while a pH of fourteen indicates a strong base, and pH of seven is neutral.
Product: The substance that results from a chemical reaction.
Reaction rate: The speed at which a chemical reaction occurs, measured as the amount of reactant converted to product in a set period of time.