All life functions are driven by chemical reactions. Biochemistry All life functions are driven by chemical reactions. Why do we need to know chemistry in biology?

A. Levels of Organization I. Introduction A. Levels of Organization Organism Organ System Organ Tissue (group of similar cells) Cell Organelle Molecule Atom

B. Elements Substance made up of only one type of atom Most of living matter is made of C, H, O, and N Familiarize yourself with: C, H, O, N, S, P, Mg, Ca, Na, Cl, K, I, Al, Fe

C. The Atom 1. smallest unit of matter that retains the properties of an element 2. Subatomic Parts: Charge Mass Location Protons Neutron Electrons Atomic nucleus 1.7 x 10-24 g ≈ 1 dalton Atomic nucleus 1.7 x 10-24 g ≈ 1 dalton 1/1840 dalton Orbitals

Proton _ _ _ _ _ _ + + + _ _ _ Neutron Electron

3.Atoms of different elements differ in their number of subatomic particles a) Atomic Number = the number of protons (and # of electrons)  protons and electrons are equal to maintain a neutral charge b) Mass Number = sum of protons + neutrons *Used as an approximation of atomic weight

Mass Number Atomic Number # Protons + Neutrons = 9 # Protons = # Electrons = 4 4

*To calculate # of neutrons: Subtract Atomic # from the Mass # 9 - 4 Atomic Number Mass Number # Protons + Neutrons = # Protons = # Electrons = 4 9 4 5 # of neutrons

atomic number # protons = # electrons = # neutrons = 2 2 2 mass number / atomic weight

c) Isotopes Atoms of the same element with the same number of protons but a different number of neutrons

(Place 1 electron per orbital before doubling up) 4. Electron Orbitals 3-D space in which electrons move around the nucleus Maximum of 2 electrons per orbital b) Orbitals are organized into energy shells that surround the atomic nucleus. *First Shell = 1 orbital = max 2 electrons **Each Shell After = 4 orbitals =max 8 electrons (Place 1 electron per orbital before doubling up) c) Valence Electrons: found in the outermost shell

5. Bohr Diagrams 2nd Shell (and higher) 4 Orbitals 1st Shell 1 Orbital

11 electrons total 1 valence electron

How many valence electrons? 4

Carbon: Oxygen:

6. Lewis Structure (dot diagram) Only shows atomic symbol and valence electrons *Use periodic table column trick Sodium: Aluminum: Nitrogen: Na Al N Carbon: Oxygen: C O