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Chemical Bonds

Chemical Bonds

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Chemical Bonds

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  1. 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

  2. Molecules • Molecules • two or more atoms bonded together • carbon dioxide (CO2), Glucose (C6H12O6), water (H2O), sodium chloride (NaCl)…

  3. 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

  4. 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

  5. Hydrogen Bonds in Water (intermolecular)

  6. 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

  7. 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

  8. 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

  9. 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+

  10. Work and Energy • Energy • capacity to do work • Kinetic energy • energy of motion • Potential energy • energy due to object’s position

  11. 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

  12. 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

  13. Energy Flow in an Exergonic Reaction

  14. 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

  15. 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

  16. 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…

  17. DehydrationSynthesis • 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)

  18. 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

  19. Hydrolysis • Splitting a polymer by the addition of a water molecule

  20. Exchange Reactions • Two molecules collide and exchange atoms or group of atoms • AB+CD  ABCD  AC + BD

  21. 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

  22. 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