chapter 2 part 1
DESCRIPTION
chemistry of lifeTRANSCRIPT
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Chapter 2
THE CHEMISTRY OF LIFE
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A. MatterMaterial that takes up space.
1. ElementsPure chemical substances
composed of atoms.Examples?How many elements exist?How many of these elements are
essential to life?
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Periodic Table of Elements
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2. AtomThe smallest “piece” of an element
that retains the characteristics of that element.
Composed of 3 subatomic particles:ProtonsNeutronsElectrons
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Characteristics of Subatomic Particles
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Atomic number# protons in nucleus of an atom
(establishes identity of the atom)
Since most atoms are electrically neutral, atomic number indicates # of electrons as well.
Mass number# protons plus # neutrons in
nucleus of an atom
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How can we determine the number of neutrons in an atom?# neutrons = atomic mass - atomic
# Determine # neutrons in a carbon
atom (atomic mass = 12; atomic # = 6).
# neutrons = 12 - 6 = 6Do all carbon atoms have the same
number of protons?Do all carbon atoms have the same
number of neutrons?
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IsotopesAtoms having the same number of
protons, but differing numbers of neutrons.
Ex. Carbon isotopescarbon 12 (12C) 6 neutronscarbon 13 (13C) 7 neutronscarbon 14 (14C) 8 neutrons
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Periodic table information on carbon:
Atomic mass given in table is average mass of all the element’s isotopes.
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3. CompoundA pure substance formed when
atoms of different elements bond.The number of atoms of each
element is written as a subscript.Examples: CO2 carbon dioxide
H2O water
CH4 methane
C6H12O6 glucose
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4. MoleculeSmallest piece of a compound that
retains characteristics of that compound.
The number of molecules is written as a coefficient.
Examples: 4CO2 4 molecules of carbon dioxide
2C6H12O6 2 molecules of glucose
6O2 6 molecules of oxygen
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5. Chemical BondsType of bond formed is determined
by the number of valence electrons in the interacting atoms [octet rule].
a) Covalent bonds - form when atoms share electron pairs.can be nonpolar or polar form molecules
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Nonpolar covalent bonds - electrons are shared equally between atoms.
Ex. methane
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Polar covalent bonds - electrons are drawn more strongly to 1 atom’s nucleus than the other.
Form when less electronegative atoms bond with more highly electronegative atoms.
Ex. water
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b) Ionic bonds - form when oppositely charged ions are attracted to each other. stronger than covalent bonds typically form salts
Ex. NaCl
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c) Hydrogen bonds - form when opposite charges on two molecules are attracted to each other.weakest type of bond*
Ex. DNA H2O
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B. The Importance of Water1. Properties Cohesion - the attraction of water
molecules for each other. Adhesion - the attraction of water
molecules for other compounds. High heat capacity – takes a great
deal of heat to raise the temperature of water.
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High heat of vaporization - a lot of heat is required to evaporate water.
Exists as solid, liquid or gas - solid (ice) is less dense than liquid.
2. SolutionsA solution is a mixture of one or more
solutes dissolved in a solvent.If solvent is water, then it is an
aqueous solution.Water is a strong solvent because it
separates charged atoms or molecules.
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3. Acids & Bases Acids - substances
that add H+ to a solution.
Bases - substances that remove H+ from solution.
pH scale is measure of acidity/alkalinity based on H+ concentration.
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C. Major Organic MoleculesMolecules that contain carbon in
combination with hydrogen.
1. Carbohydrates contain C, H & O [ C O] function to store energy & provide
supportbuilding blocks (monomers) are
monosaccharides
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Monosaccharides simple sugars containing 3 - 7 carbons.C, H, O ratio is 1:2:1
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Disaccharides simple sugars composed of 2
monosaccharides linked together by dehydration synthesis.
Other common disaccharides: maltose (seed sugar) & lactose (milk sugar).
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Polysaccharides complex carbohydrates made up of
hundreds of monomers linked by dehydration synthesis.
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2. Lipids contain C, H, O [ C >> O]do not dissolve in water
Triglycerides (fats)composed of glycerol linked to 3
fatty acid chains by dehydration synthesis.
function to cushion organs, as insulation & in long-term energy storage (adipose tissue).
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Phospholipids lipid bonded to a phosphate groupmajor component of cell membranes
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Sterols lipids that have 4 interconnected
carbon ringsEx. Vitamin D, cortisone, estrogen &
cholesterol
Waxes fatty acids combined with
hydrocarbonshelp waterproof fur, feathers, leaves
& fruits
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3. Proteinscontain C, H, O, N, (S)monomers are amino acids
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Proteins have a 3-dimensional shape (conformation):
primary (1o) structure - amino acid sequence of polypeptide chain
secondary (2o) structure - coiling & folding produced by hydrogen bonds
tertiary (3o) structure - shape created by interactions between R groups
quarternary (4o) structure - shape created by interactions between two or more polypeptides
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Examples:antibodieshemoglobin insulin & glucagonkeratinfibrin & thrombinspider silk (strongest natural fiber
known)enzymes (maltase, pepsin, lipase)
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4. Nucleic Acids contain C, H, O, N, Pmonomers are nucleotides
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DNA (deoxyribonucleic acid)5-carbon sugar is
deoxyribosenitrogenous bases
are A, G, C & Tdouble-stranded
helix held together by hydrogen bonds
is the genetic material
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RNA (ribonucleic acid)5-carbon sugar is
ribosenitrogenous bases
are A, G, C & Usingle-strandedenables
information in DNA to be expressed