Transcript Review of Chemistry

Chemistry Review
Terms and Definitions to review and Remember:
• Solution
• Atom, protons, neutrons,
electrons, isotopes,
elements, molecules, ions,
anions, cations,
compounds, covalent
bonds, ionic bonds,
hydrogen bonds, pH, acids,
and bases.
•Suspension
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Atom: smallest unit of an element
Elements differ by number of protons
http://www.perceptions.couk.com/imgs/atom.gif
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Molecule: atoms joined together with covalent bonds
Electrons are shared between atoms.
Covalent bonds are strong.
When atoms in the molecule are of
different elements, the substance is
called a “compound”.
http://www.truenorthgb.com/images/molecule.jpg
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Covalent bonds & polar molecules
Water
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Covalent Bonds: sharing
of electrons between the
oxygen and hydrogen
atoms. Strong.
Oxygen is an electron
hog; the electrons spend
more time there leaving
the hydrogen’s proton
nearly naked (and
somewhat positive):
Water is a polar molecule
mdp2.phys.ucl.ac.uk/ Talks/Ice/Ice.html
Hydrogen bonds:
• Electrical attraction between electronegative oxygen
atom and nearly naked proton.
• Bonds made between polar molecules.
• Weak bonds.
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H-bonds hold large molecules together
Example: A-T base pair in
DNA
http://www.mun.ca/biology/scarr/Fg10_16a.gif
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Hydrophilic and hydrophobic
Surfaces made of
molecules without
polar groups (e.g.
CH3CH2CH2CH2.)
repel water.
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H2O  H+ + OH-
[H+] = 10-7
pH= -log [H+]
Logarithmic
pH 7 is neutral
Ranges from 0-14
Molecules that
release H+ are acids;
those that release
OH- are bases.
http://www.btinternet.com/~chemistry.diagrams/ph_scale.gif
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Functional Groups
Chemical Reactions
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• Synthesis or decomposition reactions
– More when we cover metabolism.
• Reactants
• Substrate(s)
Products (general)
Products
(enzymatic)
C12H22O11 + H2O
2 C6H12O6
Hydrolysis (left to right) Dehydration (right to left)
+ H2O
http://www.unisanet.unisa.e
du.au/08365/timages/sucro
se.jpg
The Chemicals of life are large and small
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• Cells contain molecules of all sizes but are MADE
of large molecules called polymers
– Polymer: a large molecule made of many similar or
identical subunits.
– “poly” means “many” (polyethylene, polysaccharide)
– The small molecules that make up a polymer: monomers
• “mono” means “one”
• “oligo” means few (as in oligomer, oligonucleotide)
• In our, not all polymers are biological
– Plastics are all polymers too
Small molecules (monomers) and
macromolecules (polymers)
Ethylene and polyethylene
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Four Classes of Biological Molecules
• Carbohydrates
– Sugars and their polymers
• Nucleic acids and nucleotides
– DNA, RNA, ATP
• Lipids
– Various hydrophobic molecules
• Proteins and amino acids
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Carbohydrates: CH2O
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Monosaccharides: glucose, fructose, many others
Disaccharides: sucrose, lactose
Oligosaccharides: found on glycoproteins, in cytoplasm
(oligo- means “few”)
Polysaccharides: starch, glycogen, cellulose, agar,
chitin, xanthan gum
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A nucleotide: a monomer of DNA
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/nucleotide.gif
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Nucleic acids are the polymers made from nucleotides.
DNA
tRNA
http://www.biochem.uwo.ca/meds/medna/IMG/tRNA.GIF
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Structure of DNA
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http://academic.brooklyn.cuny.edu/biology/bio4fv/page/molecular%20biology/16-05-doublehelix.jpg
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Phospholipids are essential
building blocks for membranes;
sterol-type molecules are
rarely found in bacteria.
A lipid polymer: a biodegradable plastic
made by bacteria.
Ester bond
Polyesters
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Peptide bond
covalent bond that connects two amino acids.
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Levels of protein structure
Primary: amino acids and the
order they are in; determined
from the DNA.
Secondary: alpha helix and
beta pleated sheet; twisting
of chain in space.
Tertiary: 3D shape of protein.
Quaternary: more than 1
polypeptide combining to
form a functional unit.
http://www.contexo.info/DNA_Basics/images/proteinstructuresweb.gif
Don’t forget the water
• ALL living things require water
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Water is major component of cytoplasm
All small molecules are dissolved in water
All large molecules have water attached to them
Cells modify their chemistry to retain water
You die of dehydration before you starve
• Every polymer, every structure in the cell is
surrounded by water.
http://media.nasaexplores.com/lessons/04-070/images/faucet.jpg
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