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The Nature of Molecules

The Nature of Molecules. Lecture #2. Organisms are Chemical Machines. Organisms are Chemical Machines. Organisms are composed of molecules. Molecules are composed of atoms. Atoms. Origin of atoms Atoms make up matter. Matter has a mass (weight). Mass vs. weight Matter occupies space.

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The Nature of Molecules

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  1. The Nature of Molecules Lecture #2

  2. Organisms are ChemicalMachines

  3. Organisms are ChemicalMachines • Organisms are composed of molecules. • Molecules are composed of atoms.

  4. Atoms • Origin of atoms • Atoms make up matter. • Matter has a mass (weight). • Mass vs. weight • Matter occupies space.

  5. Question • Organisms --- molecules • Molecules --- atoms • Atoms --- ????

  6. Composition of Atoms • Atoms comprised of subatomic particles. • Protons • Electrons • Neutrons

  7. Basic Structure of the Atom • Nucleus • Shell(s) around the nucleus

  8. Basic Structure of Atom • Protons and neutrons are located in the nucleus of the atom. • Electrons orbit in outer shells.

  9. Charge of Subatomic Particles • Protons …. Positive (+) charge • Neutrons …. Neutral (no charge) • Electrons …. Negative (-) charge

  10. Weight of Subatomic Particles • Proton – weighs ~1 dalton • Neutron – weighs ~ 1 dalton • Electron – weighs ~ 1/1840 of a dalton • What is a dalton? • It is a measure of mass. • Very small • It takes 602 million million billion daltons to equal 1 gram….about the weight of a drop of water.

  11. Atomic Number vs Atomic Mass • Atomic Number -- # of protons • Atomic Mass – sum of protons + neutrons • Nitrogen as an example

  12. The Atoms of Life • There are 92 naturally occurring elements on earth. • Only 11 elements are found in greater than trace (>0.01%) amounts. • The four elements that comprise 96% of the human body are: NOCH

  13. 4 Major Elements of Life • Nitrogen – 3.3% • Oxygen – 65% • Carbon – 18.5% • Hydrogen – 9.5%

  14. Chemical BondsHold Molecules Together

  15. Ionic Bonds • One atom (sodium) donates its electron to another atom (chlorine). • Sodium becomes + (because it lost an electron). • Chloride becomes – (because it gained an electron). • Na+ is a positively charged ion. • Cl- is a negatively charged ion. • Positive and negative attract….ionic bonding….NaCl • But, when you put NaCl in water?????

  16. Water • It is the universal solvent. • A solvent is a medium in which molecules are dissolved. • A solute is the substance which is dissolved in a solvent. • So, what dissolves (or doesn’t) in water?

  17. Water • Water is a polar molecule. • Like a magnet, water is attracted to other molecules that have a charge. • When water molecules surround another molecule…it dissolves (soluble). • If a molecule doesn’t have a charge (lipids), it doesn’t dissolve (insoluble) in water.

  18. A charged molecule which will dissolve in water is said to be hydrophilic. • A non-charged molecule which won’t attract water is said to be hydrophobic.

  19. Covalent Bonds • When two atoms share one or more pair of electrons • H2 (H-H)

  20. Ionic vs Covalent Bonds • Covalent bond has no net charge. • Covalent bonds have no free electrons. • In general, covalent bonds are more stable.

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