Introduction to Biochemistry Review of Chemistry
Matter • Chemical changes in matter are essential to all life processes. • Matter: Anything that occupies space and has mass. • Mass: The quantity of matter an object has. MASS WEIGHT
States of Matter What are the 3 states of matter?
ENERGY & MATTER • Energy: The ability to do work. • States of Matter: solid, liquid, gas • Average Kinetic Energy = temperature • K.E. of atoms > from solid liquid gas
ELEMENTS • Elements are substances that cannot be broken down chemically into simpler kinds of matter. • >90% of all kinds of living things are made of combinations of 4 elements: • OXYGEN (O2) • CARBON (C) • HYDROGEN (H2) • NITROGEN (N)
CONNECTION Trace elements are common additives to food and water Trace elements are essential in minute quantities for proper biological functioning Example: iodine is a trace element that prevents goiter A goiter is an abnormal growth in the thyroid. Many foods are fortified with trace elements and vitamins (which consist of two or more elements)
COMPOUNDS • pure substance that is made up of atoms of two or more elements in a fixed ratio Different arrangements of the atoms of elements determine the unique properties of each compound • Sodium (Na) is a soft metal that explodes when placed in water. • Chlorine (Cl) is a green poisonous gas. • Sodium Chloride (NaCl) is table salt.
+ Sodium Chlorine Sodium Chloride
ATOMS the simplest particle of an element that retains all of the properties of that element
Atoms consist of protons, neutrons, and electrons • Subatomic particles • Protons and neutrons occupy the central region (nucleus) of an atom • A proton has a single positive charge • A neutron is electrically neutral • Electrons surround the nucleus • An electron has a single negative charge
LE 2-4a Electron cloud 6e– 2e– Nucleus 2 Protons 6 Protons Mass number = 4 Mass number = 12 2 Neutrons 6 Neutrons 2 Electrons 6 Electrons Heliumatom Carbon atom
Differences in Elements • All the atoms of a particular element have the same number of protons • The number of protons-the atomic number-defines the element's unique properties • An atom's mass number (atomic mass) is the sum of its protons and neutrons
# of Protons # of Protons + # of Neutrons
Isotopes are atoms with the same atomic number but different atomic masses (different number of neutrons) Isotopes
Common Isotopes and their uses • Smoke Detectors and Americium-241 • Smoke detection • Food Irradiation
Radioactive isotopes can help or harm us Radioactive isotopes are useful as tracers to study the fate of elements and molecules in living systems Radioactive tracer isotopes are often used in combination with sophisticated imaging instruments for medical diagnosis Uncontrolled exposure to radioactive material can harm living organisms
Chemical Bonding The chemical reactivity of an atom depends on the number of electrons in the outer shell
Ionic Bonds: formed when one atom gives up an electron to another. The positive ion is then attracted to a negative ion to form the ionic bond. • Form compounds • An ion is a charged atom that has lost or gained electrons in its outer shell Ionic Bonding
Covalent Bonding • A molecule consists of two or more atoms held together by covalent bonds. • Covalent Bonds: form when two atoms share one or more pairs of electrons
Polarity • In covalent bonds where the “sharing” is unequal • Because of this uneven pattern of charge, water is a polar compound.