Transcript Chemical Basis for Life

And Biochemistry
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Chemistry is important to biologists because
all of the life activities in our cells that keep
us alive are the result of chemical reactions.
◦ Matter—anything that has mass and takes up space.
◦ Elements—found on Periodic Table. Cannot be
broken down into simpler kinds of matter.
◦ HONC (Honk)—hydrogen, oxygen, nitrogen, carbon.
These are the most important elements in living
things.
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Atom—simplest particle of
an element that keeps all
the properties of that
element.
Parts of an atom
◦ Protons—positive charge
◦ Neutrons—no charge
◦ Electrons—negative charge
Inside Nucleus
Orbit Nucleus
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The atomic number is the number of
protons in an atom
The atomic mass is the number of
protons plus the number of neutrons.
The number of electrons in an atom is
the same as the number or protons
giving it a net charge of zero.
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Isotopes—atoms of the same element with
different number of neutrons.
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Compounds —atoms of two or more
elements joined by chemical bonds.
◦ Examples: H2O NaCl C6H12O6
◦ Three models below show a water molecule
Stick model
Bohr model
http://www.lionden.com/graphics/AP/
Water1.gif
Electron Cloud model
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Chemical bonds are attractive forces that
hold atoms together. They form so that
elements can become more stable by filling
their outer energy levels.
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Covalent Bonds—two atoms SHARE electrons
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Carbon has the ability to form multiple covalent
bonds
Carbon has 4 electrons in its outer shell. The
shell can hold 8. Carbon needs 4 more electrons
to become stable. This can result in big biological
molecules based around chains of carbon atoms.
http://www.chemistrydaily.com/chemistry/upload/d/d9/
Covalent.png
http://t1.gstatic.com/images?q=tbn:ANd9GcTDsTGWMhdl6_3izM7K7RCw6b5ueLWXpac
Sg91FXY8Tt6PoObw&t=1&usg=__fkitOKpfQ768Lo6SF7eDzZ0qobs=
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Many complex biological molecules will be
formed using double and triple covalent
bonds.
Double —share 2 pair of electrons
Triple —share 3 pair of electrons
Ethane
Ethylene
Acetylene
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Ionic Bonds—atoms LOSE or GAIN electrons
creating charges that attract each other.
◦ SALTS!!!!
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Chemical reactions occur when one or more
substances change to produce one or more
new substances.
Chemical equations show what happens
during the reaction
Reactants on left
Products on right
6CO2 + 6 H2O
C6H12O6 + 6O2 +energy
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Most reactions need the
addition of energy before
they will begin.
Activation Energy —energy
required for a reaction to
begin
Catalyst —speed up chemical
reactions by lowering the
activation energy required.
◦ Enzymes are common catalysts
in living things
◦ They remain unchanged
throughout the reaction.
http://xnet.rrc.mb.ca/davidb/photogallery/activatione
nergy1.gif
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Endothermic reactions
result in a net absorption
of energy
Exothermic reactions
results in the net release
of energy
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Also called Redox Reactions
◦ Electrons are transferred between atoms
◦ Oxidation reaction —a reactant loses electrons
resulting in a positive charge
 Example—Na loses an electron to become more stable
creating a sodium ion (Na+)
◦ Reduction reaction —a reactant gains electrons
resulting in a negative charge
 Example—Chlorine gains an electron to become more
stable creating a chlorine ion (Cl-)
◦ The two always occur together. One reactant gives
up what the other needs.
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Water’s chemical structure is important
in its vital role in life.
http://www.lenntech.com/images/Water%20mo
lecule.jpg
http://www.ci.rockford.il.us/uploadedImages/government/PublicWorks/Water/willing%20water
%20color.jpg
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Water is POLAR
◦ Electrons in the covalent bond are not shared
equally. Results in a partial negative charge on the
oxygen end and a partial positive charge on the
hydrogen end.
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Being polar allows water to:
◦ Dissolve many substances
◦ Form hydrogen bonds with other water molecules
creating:
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Cohesion
Surface Tension
Adhesion
Capillarity
High heat capacity
Less density when water freezes (ice floats!!)
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Solution —mixture in which one or more
substances are uniformly distributed in
another substance.
◦ Solute —dissolved substance
◦ Solvent —substance in which the solute is dissolved
◦ Concentration —amount of solute dissolved in a fixed
amount of solution
◦ Saturated Solution —no more solute can be dissolved
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Water molecules can collide and break each
other apart
H2O
H+ + OH-
OH- is known as the hydroxide ion
Free H+ ions react with water molecules:
H+ + H2O
H3O+
H3O+ is known as the hydronium ion
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Acid —solution in which the number of
hydronium ions is greater than the number
of hydroxide ions
◦ They have a value BELOW 7 on the pH scale.
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Base —solution in which the number of
hydroxide ions is greater than the number of
hydronium ions (Alkaline)
◦ They have a value ABOVE 7 on the pH scale
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Carbon—element of life
◦ Organic compounds—contain carbon (and hydrogen)
◦ Can form 4 covalent bonds with other elements so it
is the backbone of all organic compounds.
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Various functional groups can be attached to
these carbon backbones. These groups
determine how these molecules will react
with other molecules.
Functional groups can be seen on the
following chart:
Functional Group
Hydroxyl
(Alcohols)
Carbonyl (on end)
(Aldehydes)
Carbonyl (in middle)
(Ketone)
Carboxyl
(Organic Acids)
Structural Formula
-OH
H
- C=O
O
C
COOH
Amino
(Amino Acids)
NH2
Phosphate
(Nucleic Acids)
PO43-
Example
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The building of large molecules occurs as follows:
◦ Monomers —small, simple carbon molecules
◦ Polymers —consists of repeated, linked monomers
◦ Macromolecules —large polymers:
(Carbohydrates, lipids, proteins, nucleic acids)
http://kenpitts.net/bio/human_anat/monome
r.jpg
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Polymers form during condensation reactions
In these reactions; water is released
Example: Glucose and Fructose combine to form Sucrose
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Polymers break down by a hydrolysis reaction
In these reactions; water is used
http://imcurious.wikispaces.com/file/view/hydrolysis_reaction.jpg/113609729/hydrolysis_reacti
on.jpg
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Adenosine Triphosphate (ATP ) —the most
important energy currency molecule of cells.
◦ Made of Adenine; Ribose (a sugar) and 3 phosphate
groups
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The Hydrolysis of ATP is used by the cell
to provide the energy needed to drive
chemical reactions.
http://kentsimmons.uwinnipeg.ca/cm1504/atp.htm
-ATP can lose its end phosphate which releases the energy stored in it.
and makes adenosine diphosphate (ADP).
-This energy is used to do work in the cell.
-Adding the phosphate back to make ATP requires that we add energy
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Four main groups of organic compounds:
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Carbohydrates
Proteins
Lipids
Nucleic Acids
http://ez002.k12.sd.us/Chapter%20One%20Science.htm
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Used for energy
Three types:
◦ Monosaccharides
(glucose and fructose)
◦ Disaccharides (sucrose)
◦ Polysaccharides
(glycogen, starch and
cellulose)
Structure is too complex to show
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Made of chains of amino acids held together
by peptide bonds.
◦ Dipeptides (two amino acids)
◦ Polypeptides (long chains of amino acids) that fold
and bend into proteins.
Typical amino acid
Form by condensation
reactions.
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Enzymes —special types of proteins that act
as catalysts
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Lipids are fats.
Used for energy
Nonpolar
Fatty acids bonded to other molecules
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Saturated Fatty Acids —each carbon is
covalently bonded to four atoms (NO DOUBLE
BONDS)
Unsaturated Fatty Acids —not all carbons are
bonded to four other atoms (HAS DOUBLE
BONDS)
http://www.biology.lsu.edu/introbio/Link2/fatty%20acids.gif
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Triglycerides (fats) —three molecules of fatty
acid joined to one molecule of glycerol.
◦ Saturated triglycerides —the 3 fatty acids are
saturated: hard at room temp: found in butter and red
meat: “bad fats”
◦ Unsaturated triglycerides —the 3 fatty acids are
unsaturated: soft at room temp: found in plant seeds:
“good fats”
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Phospholipids —two fatty acids joined to
glycerol. They also have a phosphate group.
◦ Important part of all cell membranes
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Waxes —fatty acid chain joined to an alcohol
chain: waterproof: form protective layers in
plants and animals
Steroids —four fused carbon rings with a
functional group: include many hormones and
cholesterol
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Include DNA and RNA
Information molecules
Made of repeating
monomers called
nucleotides.
◦ Phosphate, pentose sugar,
nitrogenous base.