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Atoms_ Ions_ Molecules

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					ATOMS, IONS, MOLECULES
in BIOLOGY
ATOM: SMALLEST BASIC UNIT OF
MATTER



MACROSCOPIC : a penny




       MICROSCOPIC : atoms
ELEMENT: SUBSTANCE WITH ONLY THE
SAME TYPE OF ATOMS




         Only gold atoms   Only hydrogen
                           atoms
ELEMENTS IN ORGANISMS
   96% of human body’s mass is made of CARBON
    (C), OXYGEN (O), NITROGEN, HYDROGEN (H)

   4% of human body’s mass is CALCIUM (Ca),
    PHOSPHORUS (P), POTASSIUM (K), SULFUR
    (S), SODIUM (Na)
  COMPOUND: SUBSTANCE W/ TWO OR
  MORE DIFFERENT TYPES OF ELEMENTS

                   ATOMS




COMPOUNDS
COMPOUNDS IN LIVING THINGS
   Water (H2O)



   Carbon dioxide (CO2)
IONS: ATOM THAT GAINED/LOST
ELECTRONS
   Positive ion: lost electrons

   Negative ion: gained electrons

   Ionic bond: ions held together by attraction of +
    and – charges
IONS IN YOUR BODY
   Hydrogen ions (H+): needed in cells to produce
    usable chemical energy

   Calcium ions (Ca2+): muscle movement

   Chlorine ions (Cl-): chemical signals in brain
COVALENT BOND: WHEN ATOMS
SHARE A PAIR OF ELECTRONS
   Molecule: two or more atoms held together by
    covalent bonds

   Almost all substances that make up organisms
    are molecules held together by covalent bonds
WATER AND ITS FUNCTION
in BIOLOGY
WATER IS A POLAR MOLECULE.
      Polar molecules have slightly charged regions.


                           _



                           O
                       H       H
                   +               +


 – Nonpolar molecules do not have charged regions.
 – Hydrogen bonds form between slightly
 positive hydrogen atoms and slightly negative
 oxygen atoms.
Hydrogen bonds are responsible for three important
 properties of water.
   1. high specific heat: water can resist changes in
       temperature.
      • Water absorbs heat during cell processes to
          help regulate cell temperature.
   2. Cohesion: molecules attract each other in a
       substance.
      • Produces surface tension.
   3. Adhesion: molecules of different substances
       attract each other.
      • Water in glass tube.
MANY COMPOUNDS DISSOLVE IN WATER.
    A solution is formed when one substance dissolves in
     another.
      A solution is a homogeneous mixture.
      Solvents dissolve other substances.
      Solutes dissolve in a solvent.




         solution
   “Like dissolves like.”
     – Polar solvents dissolve polar solutes.
     – Nonpolar solvents dissolve nonpolar solutes.
     – Polar substances and nonpolar substances
       generally remain separate.
SOME COMPOUNDS FORM ACIDS OR BASES.
    An acid releases a hydrogen ion when it dissolves in
     water.
      high H+ concentration
      pH less than 7

                     stomach acid pH between 1 and 3




                                    more acidic
   A base removes hydrogen ions from a solution.
     – low H+ concentration
     – pH greater than 7
              bile pH between 8 and 9




                      more basic
   A neutral solution has a pH of 7.

                      pure water pH 7
PH IN ORGANISMS
   Humans need to stay near neutral pH

   Small changes in pH can disrupt cell processes

   Azalea plans thrive in high pH soil

				
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posted:8/27/2012
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