Chemical Bonds• The interaction between 2 atoms may result in the

formation of a chemical bond whereby 2 atoms are chemically linked to one another– 2 major types

• Ionic• Covalent

• Atoms bond with one another to become stable– an atom is stable when the valence shell is

completely full (satisfying the “octet rule”)• Groups of atoms that are associated with each other

through bonds are called molecules– chemicals that are LARGER and structurally more

CoMpLeX than individual atoms

Molecules• Molecules

– two or more atoms bonded together • carbon dioxide (CO2), Glucose (C6H12O6), water

(H2O), sodium chloride (NaCl)…

Nonpolar and Polar Molecules

• Nonpolar molecules include those containing a high number of nonpolar covalent bonds and few polar covalent bonds (very little or no O and/or N)– lipids (fats)

• uncharged (neutral) molecules • Polar molecules include those containing a

moderate number of polar covalent bonds (moderate amounts of O and/or N)

• include every other substance:– carbohydrates, proteins, nucleic acids, water…– ions (cations and anions)

• charged molecules

Hydrogen Bonds

• Electrical attraction between a polar covalently bound H (has a partial positive charge) and a covalently bound electronegative atom (O/N) (has a partial negative charge)

• Too weak to bind atoms together – serve as intramolecular (within molecule) bonds

• aids in the stabilization of very large molecules • observed in proteins and nucleic acids

– serve as intermolecular (between molecules) bonds• holds 2 or more molecules in close proximity to

one another• observed in between water molecules

Hydrogen Bonds in Water (intermolecular)

Water

• The most abundant molecule of the human body – 70% of body mass (weight) is attributed to water

• Polar substances mix easily with other polar substances, but do not mix with nonpolar substances (REMEMBER THIS)

• Nonpolar substances mix easily with other nonpolar substances, but do not mix with polar substances (REMEMBER THIS)– like dissolves like

• The majority of the chemicals found in the body are polar, however lipids are molecules essential for proper functioning of the body

Polarity (Water vs Lipids)

• All polar chemicals mix with water and are considered to be hydrophilic (water loving)– polar chemicals that mix with water will not mix with

lipids and are considered to be lipophobic (lipid fearing)

• All nonpolar chemicals mix with lipids and are considered to be lipophilic (lipid loving)– Nonpolar chemicals that associate with lipids will

not mix with water and are considered to be hydrophobic (water fearing)

• Polar = hydrophilic = lipophobic• Non-polar = hydrophobic = lipophilic

Properties of Water• Solvency

– ability to dissolve matter• because water is the most abundant compound

in the body it is the universal solvent • environment for all metabolic reactions• provides a means for the transport of substances

from one location in the body to another• Adhesion and Cohesion

– molecules of water “stick” to themselves and other types of molecules• due to hydrogen bonds

• High heat capacity• prevents rapid increases or decreases in

temperature

Biochemical Reactions• The functioning of the body (physiology) occurs as the

organic molecules of the body react with one another • Written symbolically with chemical equations

– relative amounts of reactants (starting chemicals) and products (finishing chemicals)

– number and type of reacting substances, and products produced• C6H12O6 + 6O2 6H2O + 6CO2

• Chemical reactions occur when covalent bonds in a molecule are formed or broken– the formation of a covalent bond uses energy– the breaking of a covalent bond releases energy

• All chemical reactions are theoretically reversibleA + B ↔ AB CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+

Work and Energy

• Energy – capacity to do work

• Kinetic energy – energy of motion

• Potential energy– energy due to object’s position

Energy Sources

• Energy sources that the body uses includes:– Chemical

• stored in the covalent bonds of energy-rich molecules (potential)

– Electrical• the movement of ions (potential and kinetic)

– Heat • causes molecules to move (kinetic)

– Mechanical • moving molecules collide with one another which

transfers energy between the two molecules (kinetic)

• Energy sources can be converted from one form to another

Metabolism and Biochemical Reactions• All of the collective biochemical reactions of the body

are grouped into two general classes:– Catabolic (exergonic) reactions

• decomposition reactions that release energy (due to bonds breaking) in the form of HEAT into the environment of the reaction

• reactants contain more energy than the products – Anabolic (endergonic) reactions

• synthesis reactions that remove (store) energy (HEAT) from the environment of the reaction to create bonds

• products contain more energy than the reactants• All reactions must overcome the activation energy

before the reaction takes place– energy required to bring reactants together

Energy Flow in an Exergonic Reaction

Organic Molecules• Molecules unique to living systems contain carbon and

are referred to as organic molecules• Most of the anatomy and physiology of the body is

provided by the interaction between 4 different classes of organic macromolecules

• Each class consists of small molecular subunits called monomers (one unit)– smallest subunits of macromolecules that exhibit

chemical properties of the macromolecule• Monosaccharide (carbohydrates)• Fatty acid (lipids)• Amino acid (proteins)• Nucleotide (nucleic acids)

– able to function individually or in covalently bound groups

Biologically Important Organic Molecules

• Monosaccharides– basic (smallest) unit of carbohydrates (sugars)

• Amino acids– basic (smallest) unit of proteins

• Fatty acids– basic (smallest) unit of lipids (fats)

• Nucleotides– basic (smallest) unit of nucleic acids

Synthesis Reactions of Macromolecules

• Monomers can be covalently bound to one another to create a molecule gets progressively larger resulting in a polymer (many units)

• Two or more small molecules combine to form a larger one

• A+B AB+C ABC+D ABCD…

Dehydration Synthesis

• 2 monomers are covalently bonded together to form a a new molecule that is larger and structurally more complex by the removal of a water molecule (dehydration)

Decomposition Reactions

• Large polymer molecules can be reduced down to the individual monomers by breaking the covalent bond between monomers through a decomposition reaction

• ABC AB+C A+B+C

Hydrolysis

• Splitting a polymer by the addition of a water molecule

Exchange Reactions

• Two molecules collide and exchange atoms or group of atoms

• AB+CD ABCD AC + BD

Oxidation-Reduction (Redox) Reactions

• Involves the transfer of electrons from one atom/molecule to another– eg. formation of an ionic bond

• Reactants losing electrons are become oxidized (Loss Electron(s) Oxidation = LEO)

• Reactants gaining electrons are become reduced (Gain Electron(s) Reduction = GER)

• Na + Cl → Na+ + Cl- – Na is oxidized and Cl is reduced

Reaction Rates• The rate of chemical reactions are determined by

molecular motion and collisions between chemicals• The speed at which a chemical reaction proceeds is

affected by:– the concentration of reactants

• more concentrated = more collisions = faster rate– the temperature

• higher temperature = faster molecular movement = more collisions = faster rate

– the presence of catalysts• “molecular matchmakers”

–bring reactants together faster• biological catalysts are proteins called enzymes