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. MASSWEIGHT

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

Physical and Chemical Changes

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 (O 2 )  CARBON (C)  HYDROGEN (H 2 )  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 ChlorideChlorineSodium +

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 Protons Neutrons Electrons Helium atom Mass number = Protons Neutrons Electrons Carbon atom Mass number = 12 Electron cloud Nucleus 2e – 6e –

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

Isotopes  Isotopes are atoms with the same atomic number but different atomic masses (different number of neutrons)

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 Bonding  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

Covalent Bonding  Covalent Bonds: form when two atoms share one or more pairs of electrons A molecule consists of two or more atoms held together by covalent bonds.

Polarity  In covalent bonds where the “sharing” is unequal  Because of this uneven pattern of charge, water is a polar compound.