Chapter 2

• Matter - Anything that has mass and occupies space
• Mass - how much matter an object has
• Weight - measure of how strong gravity pulls on matter (mass=weight)

• The simplest chemical substances
• 92 naturally occurring
• 98% of body weight is made up of oxygen, carbon, hydrogen and nitrogen
• Magnesium 0.06% - cofactor for many enzymes
• Iron 0.007% - essential for oxygen transport and energy capture

Smallest unit of matter that maintains all the properties of an element

• Protons - positive charge; found in atomic nucleus; mass of 1 Dalton
• Neutrons - no charge; found in atomic nucleus; mass of 1 Dalton
• Electrons - no charge; found in electron cloud - orbits nucleus; mass is 1/2000th of a Dalton (negligible)

• Defines mass of an atom
• equal to number of protons + number of neutrons
• approximation only (ignores electrons)
• written as a superscript ²³Na

• Actual mass of the atom (including electrons)
• Will be close to the mass number
• Written below symbol on periodic table
• This number can be rounded for mass number

• Defines the element
• Equal to the number of protons in the nucleus
• assuming atom is neutral it is also equal to the number of electrons
• written as a subscript ₁₁Na
• written above symbol on periodic table

• Different atomic forms of an element
• Atoms with same atomic number can differ in # of neutrons
• If an isotope is unstable (radioactive) nucelus decays and emits energy

Amount of time for half of a given amount of an isotope to decay

• Protons and neutrons in nucleus
• Electrons orbit at fixed distances (eloectron cells)
• Maximum in first shell 2 electrons, max in second and third 8 electrons
• Atoms want outer (valence) shell filled
• electrons in valence shell are valence electrons
• Atoms with incomplete valence shells are reactive; atoms with complete valence shells are unreactive

Attraction between two atoms caused by sharing or transferring of valence electrons

Sharing of a pair of electrons between two atoms (forms a molecule)

the attraction of a particular kind of atom for the electrons of a covalent bond (how stingy are the atoms)

• Generally occurs between atoms with the same electronegativity
• Equal sharing of electrons
• H-H one pair of electron shared - single covalent bond
• O=O two pairs of electrons shared - double covalent bond

• Occurs between atoms with different electronegativity
• Unequal sharing of electrons
• Water is a polar covalent bond; oxygen has greater electronegativity

• Transfer of electrons from one atom to another
• Highly electronegative atom "strips" electron from another atom
• Strength varies (depends on enviroment)

• Occurs between H atom of 1 polar covalent bond and N or O of another covalent bond
• Weak bond

• Making or breaking of chemical bonds that leads to chanes in composition of matter
• Cannot create or destroy matter only rearrange atoms and bonds
• Reactant - starting materials
• Product - resulting materials

• All the reactions in the cells/tissues of the body at a given moment
• Work -movement of an object or change in physical structure of matter
• Energy - capcity to perform work
• Kinetic energy - energy of motion
• Potential energy - stored energy

• breaking down molecules
• Catabolic reaction splits water and adds H and OH to products

• building up molecules
• Dehydration synthesis (condensation) - anabolic reaction form water by removing H and OH from reactants

• Proteins that selectively speed up chemical reactions without being changed
• Lower activatgion energy (the energy required to start a reaction)

Energy released (also called exothermic)

Energy absorbed (also called endothermic)

Reactants in an enzymatic reaction

• groove in an enzyme that binds one or more substrates (grooves made by tertiary protein structure)
• Enzyme substrate complex - allowed for interaction of substrates and enzyme to take place
• Specific for substrate (lock and key model)
• Enzyme brings molecule together allowing synthesis/decomposition reactions

• Supports life (cells are 70-90% water) and participates in some reactions
• Dissolves organic/inorganic molecules
• High heat capacity (absorbs/retains heat)
• Effective lubercant in the body

• Substance that does the dissolving
• Water is the solvent of life

Substance that is dissolved

Solute + Solvent

• When water is the solvent
• Good solvent due to polarity
• Water forms hydration sphere (shell) around ions that breaks down compound

Compunds that dissociate in water and release ions

• Hydrophilic - polar substance interacts with water
• Hydrophobic - non-polar substance does not interact with water

Solute that dissociates in solution and releases free hydrogen ions (H⁺)

• Solute that dissociates in solution and releases hydroxyl ions (OH^-)
• Binds to hydrogen ions to form water

• Measures concentration of hydrogen ions
• pH = -log[H⁺]

• Compunds that stabilize the pH of a solution by removing or adding hydrogen ions
• Maintain pH of body fluids within normal limits

• CO₂ + H₂O <-----------> H₂CO₃ <----------> HCO₃^- + H⁺
• Carboxyl Acid Bicarbonate

ranges from 7.35 - 7.45

• Acidosis <7.35 produces coma
• Alkalosis >7.45 produces sustained skeletal muscle contractions