The Chemistry of Life Domains of Study Domain of BioMolecules Domain of Cells Domain of Organisms Domain of Populations Domain of Communities 2007-2008

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 –

Different kinds of atoms = elements The World of Elements H C N O Na Mg P S K Ca Different kinds of atoms = elements

atoms Atomic # = number of protons Atomic Mass = protons + neutrons How do you figure out how many neutrons in an atom? Electrons?

??? Practice N 7 14 B 5 11 H 1 C 6 12 Symbol Atomic number Mass number Protons Neutrons electrons N 7 14 B 5 11 H 1 C 6 12 ???

Isotopes! Same element Different number of neutrons Mass number relates to the particular isotope C14 and C12

Medical uses for radioactive isotopes A PET scan is one of the many medical uses for radioactive isotopes PET, short for positron-emission tomography, can detect intense chemical activity in the body. Brightly colored areas indicate elevated levels of radioactively-labeled glucose and high metabolic activity, which is a strong indicator of cancerous tissue.

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?

This tendency drives chemical reactions… 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 – –

Bonds in Biology Covalent Bonds: atoms share electrons (strong) Hydrogen bond Bonds in Biology H2O Covalent Bonds: atoms share electrons (strong) Ionic bonds: give/take electrons and oposites attract Van der Waals forces Hydrogen Bonds!! H2O Covalent bond – H2 (hydrogen gas)

Letters are used to represent the elements Chemical Formula A chemical formula shows the kinds and number of atoms in a substance. Letters are used to represent the elements 3H O Number of molecules 2 Subscript is used to represent the # of each element (for example 2 Hydrogens) ones are assumed

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)

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 –

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

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 + – – – – +

Ionic Bonds Electrons are transferred from one atom to the other making them charged ions. Opposites attract

All compounds have properties that are different from the elements that make them. These are called Emergent Properties

Emergent properties +

CHEMICAL REACTIONS: energy + 6CO2 + 6H2O  C6H12O6 + 6O2 Describe the process in which elements react to form new compounds. Result in the release or absorption of energy. Ex. What does this chemical equation represent? energy + 6CO2 + 6H2O  C6H12O6 + 6O2 Sunlight + 6 carbon dioxide + 6 water molecules reacts to form glucose + 6 oxygen gas molecules

Any Questions? Do one brave thing today…then run like hell! He’s gonna earn a Darwin Award! Any Questions? Do one brave thing today…then run like hell!