Chapter 3: Part I Biochemistry

Matter: Anything that has mass and takes up space – can be solid, liquid or gas Atom: Smallest unit of matter that cannot be broken down by chemical means

Parts of an atom: Protons (+) Electrons (-) Neutrons (0) Protons and neutrons are found in the nucleus Electrons orbit electron clouds around the nucleus

Inner energy level holds two electrons Other energy levels holds eight electrons The number of electrons in the outer energy shell determines the chemical properties of the atom.

Using the periodic table:

Atomic number = # of protons Atomic mass = # of protons + neutrons If number of protons = number of electrons, atom is neutral (no charge) Elements are arranged horizontally in order of increasing atomic number Elements are arranged vertically according to the number of electrons in the outer shell

Isotopes: atoms that differ in their number of neutrons Carbon has 3 isotopes: Carbon 12 (most abundant) Carbon 13 Carbon 14 (radioactive - unstable)

Atom is most stable when the outer shell is filled Number of electrons in outermost shell = valence electrons Ex: Helium – 2 electrons in 1st shell Neon – 8 electrons in 2nd shell Elements in last column of periodic table have filled outer shells – Noble gases To become stable, atoms form bonds with other atoms

Molecules: A group of atoms held together by covalent bonds Ex: O2 or CO2 Compound: A substance made of the bonded atoms of two or more different elements. Ex: CO2 or C6H12O6

Chemical/molecular formula: shows kind and proportion of atoms of element/molecule Ex: 5HCl 8C 14Fe 6H2O C6H12O6 3CO2 Na+ N2

Structural formula: Shows the arrangement of atoms within the molecule

Types of bonds: ionic bonds, covalent bonds & hydrogen bonds Ion – an atom that has an electric charge because it has gained or lost electrons Ions with opposite charges (- or +) are attracted to each other and form an ionic bond. Ionic bonds – the attractive force between two oppositely charged ions

Ionic Bonds

In covalent bonds, atoms share electrons Animation

Solution – a mixture in which ions or molecules are evenly distributed in another substance Some water molecules break apart to form ions Hydronium (H3O+) Hydroxide (OH-) In water, the balance of these ions is equal In solutions such as acids and bases, the number of hydronium and hydroxide is unequal

Acids are any compound that increases the number of hydronium ions when dissolved in water HCl  H+ + Cl- H20 and H+ combine to form H3O+

Bases are any compound that increases the number of hydroxide ions when dissolved in water (also called alkaline). NaOH  Na+ + OH-

pH – a measure of how acidic or basic a solution is Acid – pH 0-6 Base – pH 8-14 Neutral - 7

Buffers: a substance that reacts to prevent pH changesd in a solution – do so by taking up excess H+ or OH- ions. Help maintain pH in blood, stomach acid, urine, and intestinal fluid – example of how your body maintains homeostasis!!!