Biochemistry Study of chemical reactions that take place in our body everyday Chemical reactions allow us to remain alive – Rearrangement of chemical bonds to form products from reactants

Chemical Fundamentals Review Living things are composed of matter. Matter has mass, occupies space. Atoms composed of: – Small nucleus Proton (positive charge) Neutron (no charge) – Surrounded by Electrons (negative charge)

Isotopes Atoms of an element with the same atomic number but a different mass number – Number of protons ALWAYS stays the same – Number of neutrons changes which distinguishes isotopes from one another – All isotopes of an element have the same chemical properties (electrons) Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14 6 electrons 6 protons 6 neutrons 6 electrons 6 protons 8 neutrons 6 electrons 6 protons 7 neutrons

Radioisotopes (Carbon 14) Isotope with radioactivity Not stable Spontaneously decay into other forms Half life – The time it takes for one half of the nuclei sample to decay

Radioactive Tracers Used to identify abnormal bodily processes Designed to mimic naturally occurring substances (glucose) – Thyroid – iodine – Bones – phosphorous – Muscles – potassium PET – Positron emission tomography

Why Are Electrons so Important? Chemical behaviour of an atom: -Electron configuration - distribution of electrons in the atom’s electron shells - valence electrons – outermost electrons in an atom’s electron shell - incomplete valence shells are chemically reactive (bond formation)

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to H would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons Gain 1 electron

Atoms bond to form compounds Compounds are made up of at least 2 different kinds of atoms (e.g., H 2 O) Bonds are formed by the sharing or transfer of electrons 2 Types of Chemical Bonds Ionic Bonds Covalent bonds

Ionic Bonds - occur when one atom donates or gives up one or more electrons (metal + non-metal) Ionic Compound ( Na + Cl - ) Salt crystals Opposite charges attract to form ionic bonds

Covalent Bonds – involve a sharing of a pair of valence electrons between atoms (non-metal + non-metal)

Single covalent bond Double covalent bond Four single covalent bonds Two single covalent bonds

2 Types of Covalent Bonds Polar CovalentNon-polar covalent Equal sharing of electrons Unequal sharing of electrons Determined by the atoms ELECTRONEGATIVITY E.g. CH ₄ E.g. H 2 O

Electronegativity The measure of an atom’s attraction for additional electrons Polar Covalent Bond -unequal sharing of electrons between two atoms with different electronegativity results. Non-Polar Covalent Bond -equal sharing of electrons between two atoms. Electronegativity = Stronger pull of shared electrons

The electronegativity difference (∆En) is the difference in electronegativity number between two atoms participating in a covalent bond.

Electronegativity Differences

Molecular Polarity Depends on – Distribution of charges – Symmetry Polar Molecules – One side, or end of molecule has a slight positive charge, and the other side, or end, has a slight negative charge – Occurs when the molecule is not completely symmetric Non-polar Molecules – Molecule is completely symmetric – All atoms attached to central atom are the same – Hydrocarbon

Polar or Non-Polar?

VSEPR Valence shell electron pair repulsion Electrons repel one another forming the shape of the molecule Includes both bonded electron pairs and non- bonding electron pairs (lone pairs)

Polar Molecules Align themselves to other polar molecules to create stability – Hydrogen bonding (DNA) Soluble in water (polar) and non-polar organic solvents (turpentine)

Importance of Polar and Non-Polar Molecules Hydrophobic properties of fatty acids in phospholipids (cell membrane) Consumption of antioxidants in our diet (vitamin C) ATP – energy currency of cell DNA – double helix structure Enzyme catalyzed reactions Water – universal solvent

Intermolecular Forces intermolecular forces of attraction exist between molecules Influence physical properties of a molecule – (Solubility, Melting point, Brittleness etc) Intermolecular forces are known as van der Waals forces.

Example of van der Waals Forces Hydrogen Bonds – Strongest and most biologically significant – Crucial to function of cells and cellular processes (DNA replication) – Weaker when compared with ionic and covalent bonds – Example WATER – Properties are high heat capacity, high melting point and boiling points, cohesion, adhesion, surface tension

Chemical Reaction Breaking and formation of chemical bonds rearranging atoms and ions 4 Types – Dehydration – Hydrolysis – Neutralization – Redox reactions

Dehydration Also called condensation reactions Removal of a –OH (hydroxyl group) and a -H (hydrogen) from reactants to form a water molecule Most common reaction used by cells Assemble complex carbohydrates and proteins

Hydrolysis Reverse of dehydration reactions A water molecule is used to split a larger molecule A hydroxyl group and a hydrogen attach to small sub units Two products are formed

Neutralization Acid reacts with a base to form water and a salt Acid + Base Salt + Water

Redox Electrons are lost from one atom and gained by another Oxidation is loss of electrons (OIL) Reduction is gain of electrons (RIG) Responsible for most energy transfers in cells

Carbon Makes up the base of every organic molecule Form 4 covalent bonds (single, double, triple) Hydrocarbons – Long chains, rings, or branched structure of carbon Chains can be linear or branched

Carbon In Biological Molecules Carbon mostly bonds with – Hydrogen – Nitrogen – Sulfur – Oxygen These elements provide biological molecules with different functional properties Four categories – Carbohydrates – Proteins – Nucleic Acids – Lipids

Functional Groups Found on all 4 major classifications of biologically important molecules Small reactive groups that participate in chemical reactions Usually ionic or strongly polar (helps to initiate chemical reactions) Form different types of bonding

Find the Functional Groups