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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

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chemical bonds
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
    • two or more atoms bonded together
      • carbon dioxide (CO2), Glucose (C6H12O6), water (H2O), sodium chloride (NaCl)…
nonpolar and polar molecules
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
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
  • 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
Polarity (Water vs Lipids)
  • All polar chemicals mix with water and are considered to be hydrophilic (waterloving)
    • polar chemicals that mix with water will not mix with lipids and are considered to be lipophobic (lipidfearing)
  • All nonpolar chemicals mix with lipids and are considered to be lipophilic (lipidloving)
    • Nonpolar chemicals that associate with lipids will not mix with water and are considered to be hydrophobic (waterfearing)
  • Polar = hydrophilic = lipophobic
  • Non-polar = hydrophobic = lipophilic
properties of water
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 andCohesion
    • 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
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 bonduses energy
    • the breaking of a covalent bond releases energy
  • All chemical reactions are theoretically reversible

A + B ↔ AB CO2 + H2O ↔ H2CO3↔ HCO3- + H+

work and energy
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
  • 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
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
organic molecules
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
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
Synthesis Reactions of Macromolecules
  • Monomers can be covalently bound to one another to create a molecule gets progressively larger resulting in a polymer (manyunits)
  • 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
Decomposition Reactions
  • Large polymer molecules can be reduced down to the individual monomers by breaking the covalent bond between monomersthrough a decomposition reaction
  • ABC  AB+C  A+B+C
hydro lysis
  • Splitting a polymer by the addition of a water molecule
exchange reactions
Exchange Reactions
  • Two molecules collide and exchange atoms or group of atoms
  • AB+CD  ABCD  AC + BD
oxidation reduction redox reactions
Oxidation-Reduction (Redox) Reactions
  • Involves the transfer of electrons from one atom/molecule to another
    • eg. formation of an ionic bond
  • Reactants losingelectrons are become oxidized (Loss Electron(s) Oxidation = LEO)
  • Reactants gainingelectrons are become reduced (Gain Electron(s) Reduction = GER)
  • Na + Cl → Na+ + Cl-
    • Na is oxidized and Cl is reduced
reaction rates
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