Transcript General Chemistry and Water

General Chemistry
Review for the biological sciences
Chemical Elements
• Each element consists of unique atoms
• Represented by symbols—H, Na, Au, etc.
• 92 naturally occurring elements
(what are they?)
– About 25 are considered essential to life
– 4 make up > 95% of living matter
• Carbon
• Hydrogen
• Oxygen
• Nitrogen
Chemical Elements
• Other significant elements
– Ca, P, K, S, Na, Cl, Mg
• Trace elements
– Fe, I, Cu, Zn, Co
Atoms
• The smallest particle
of an element that has
the qualities of that
element
• Made up of smaller
sub-atomic particles
• Cannot be broken
down into simpler
substances by ordinary
means
Sub-atomic particles
Neutrons
•neutral (no) charge
•symbol n0
•mass = 1+ amu
nucleus
Protons
•positive charge
•symbol p+
•mass = 1 amu
+ +
Electrons
•negative charge
•symbol e•located in electron cloud
•Mass = 1/1840th amu
The atom (He)
The attractions between the positive
charges in the nucleus and the
negative charges of the electrons
keep the electrons in the vicinity of
the nucleus.
molecules
• Atoms of two or more different types
chemically combined
• Chemically different than the atoms that
make them up
• Molecules combine to form compounds
water: a colorless, odorless
liquid (at ordinary temps);
necessary for life
a water molecule
H2O
Hydrogen: a colorless,
odorless gas; explosive!
oxygen: a colorless,
odorless gas; supports
combustion
So…how are atoms held together
in a molecule?
CHEMICAL BONDS!
• Ionic: the giving and taking of electrons
• Covalent: the sharing of electrons
• Hydrogen: the attraction of + and -
Ionic Bonds
• Exchange of electrons
– One atom takes
electrons & the other
donates them
• Forms charged
particles called ions
• ex—sodium chloride
Covalent Bonds
• Sharing of electrons
• Between nonmetals
– Cl + Cl
– CH4
Covalent
Bonds
Non-polar
Polar
Covalent Bonds
non-polar
• Equal sharing of
electrons between
two or more atoms
• Carbon, Hydrogen
– CH4
– C2H6
polar
• Unequal sharing of
electrons between
atoms
• Forms polar
molecules
• Water, sugar, alcohol
Hydrogen bonds
• The attraction between
the +charged portion of
one polar molecule and
the –charged portion of
another molecule
• Found in water,
proteins, DNA
Moving on to the chemistry of living things…
CARBON AND
MACROMOLECULES
Carbon is the backbone
• Carbon has 4 valence
electrons
• =Versatility
– Chains (straight or
branched)
– Rings
– Single, double and triple
bonds
– Isomers
Functional Groups
• Certain groups of
atoms that may be
attached to a carbon
skeleton and give
organic compounds
distinctive features.
• Attachments that
replace one or more of
the hydrogens bonded
to the carbon skeleton
http://yellowtang.org/images/five_principal_func_c_la_784.jpg
Biomolecules or Macromolecules
• Polymers produced by living things
• Polymers are
– Large molecules
– made up of smaller, repeating units called
monomers
• Monomer + monomer + monomer + …..
creates the polymer
– Condensation reaction/dehydration synthesis/
polymerization
• Reverse reaction is hydrolysis
Polymer
examples
monomers
Carbohydrates
Starches, cellulose,
Pasta, potatoes, etc.
Simple sugars
Lipids
Fats, oils, waxes
Glycerol & fatty
acids
Proteins
Meat, muscle tissue,
enzymes, hair, etc.
Amino acids
Nucleic acids
DNA & RNA
nucleotides
THE END