The Chemistry of Life
Atoms
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All matter is made up of _____________________, which are substances that cannot be broken down into
smaller substances in a chemical reaction.
An__________________, the fundamental unit of matter, is the smallest unit of an element that displays all of
that element’s characteristics.
Atoms contain the following subatomic particles:
o ____________________ positively charged particles located with the atomic nucleus, or core of the
atom
o ___________________ Electrically neutral particles located within the atomic nucleus.
o ___________________ Negatively charged particles orbiting in a cloud around the atomic nucleus
electron
neutron
proton
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Atoms are described by their __________________________ and _______________________
_______________________________ indicates the number of protons in an atom.
______________________________ indicates the combined number of protons and neutrons in an atom
Atom’s chemical symbol, the written representation of an atom includes atomic number, mass number, any
charge on the atom.
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Atomic Behavior
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Is largely determined by the number and arrangement, or _________________________, of electrons
_______________________ its nucleus.
Electrons move about in regions called___________________________located at varying distances from the
nucleus.
Electron Shells
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All of an atom’s electrons are arranged in orbitals located at different energy levels, called
________________________, around the nucleus.
Shells further away from the nucleus requires ________________________.
Electrons tend to __________________toward lower __________________ positions and will fill orbitals in the
lowest electron shells before filling orbitals in electrons shells farther out.
Each electron shell has a maximum number of orbitals, and therefore ______________ that it can hold:
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First electron shell – maximum one orbital- ________ electrons
Second electron shell- maximum 4 orbitals- _________ electrons
Third electron shell- maximum 4 orbitals – _________ electrons
Four electron shell- maximum 4 orbitals- __________ electrons
Valence Electrons
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Occupy the energy shell ________________________ from the nucleus.
Atoms with a full complement of electrons in their outermost shell are more_______________  and less reactive.
These valence electrons will help in the forming of _____________________________
Example:
o Sodium 11Na has 11 electrons. Two electrons in the first shell, 8 in the second shell and 1 in the last (3rd
shell). To create a full outer shell electrons, a sodium atom loses the single valence electron from the third
shell.
o In contrast, chlorine, 17Cl has seventeen electrons. Two in the first orbital, 8 in the second orbital, 7 in the
third orbital. To create a full outer shell electrons, a chlorine atom gains one electron.
Ions
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An __________________ is an atom that has acquired a positive or negative electric charge by gaining or losing
electrons.
There are two types of ions:
_________________________ is an atom that has lost electrons and acquired a positive charge (Example: Sodium)
_________________________is an atom that has gained electrons and acquired a negative charge (Example:
Chlorine)
Example: Potassium (K) can lose an electron to become a cation, K+. Sulfur (S) can lose two electrons to become an
anion, S-2
Isotopes
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Are atoms of the same element that have different number of _______________________and therefore different
___________________________.
Example: There are three naturally occurring carbon isotopes, each with a different atomic number: Carbon -12,
Carbon-13, and Carbon-14. As represented in the atomic number, carbon-14 has one more neutron than carbon-13
and two more neutrons than carbon-12
Radioactive Isotopes
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Are highly ____________________ and ____________________ decay by losing protons or neutrons along with
energy. The rate of decay is _____________________ for any given isotopes
__________________________ is a measure of the amount of time it takes for half of the atoms in that substance
to decay
All living organisms are composed of ______________________ and ______________________ in a certain ratio,
designated by the variable x.
Half life of carbon-14 is ____________________ years and will decay to _______________________
Scientist measure the ratio of radioactive isotopes such as carbon-14 against other elements present in a fossil to
determine the approximate age of the fossil.
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Example: The age of a bone fossil that contains carbon-14 and carbon-12 in a ratio of 1/8 x can be dtermined using
the half-life of carbon-14. Because one-eighth is (1/2)3, three half-lives have passed for carbon-14 presnet in this
fossil. Three times 5,730 equals 17, 190; therefore the fossil is approximately 17, 190 years old
Chemical Bonds
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Are the interactions between the electrons of _________________________________
__________________________- is the strength of the attraction an atom has for its electrons, helps determine the
nature of the chemical bonds that atom can form.
The more attraction electronegative an atom is, the greater the____________________of its attraction for
electrons.
Covalent Bonds
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Two or more atoms _______________________ valence electrons.
Covalent bonds result in the formation of molecules, which are _____________________ associations between
two or more atoms
Atoms joined by covalent bonds may share one, two, or three ____________________resulting in single,
double, or triple bonds.
The distribution of shared atoms in a covalent bond depends on the _______________________ of the atoms.
Two terms to describe the way electrons are shared:
___________________________________ form between atoms that have similar electronegativity. The
electrons in a nonpolar covalent bond are shared equal between the two atoms.
__________________________________ form between atoms that have different electronegativities. Valence
electrons in a polar covalent bond will be more attracted to the atom of higher electronegativity, resulting in a
partial negative charge on that atom and partial positive charge on the other atom.
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Ionic Bonds
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Form when electrons are _____________________ from an atom of low electronegativity to an atom of high
electronegativity.
The atom that _____________ an electron becomes ______________________ charged anion, while the atom
that has _______________ an electron becomes a ________________ charged cation.
Cations and anions are mutually _______________________ to one another by their charges.
This mutual attraction results in the formation of a__________________________, which is a highly regular and
ordered solid whose atoms are arranged in repeating units.
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Hydrogen Bonds
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The __________________ of all chemical attractions, form when a hydrogen atoms that is
______________________ bonded to an electronegative atom is attracted to another electronegative atom,
generally either oxygen (O) or nitrogen (N).
Hydrogen bonds are one of the main forces that give proteins their ___________ shapes
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Water
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________________________ is the most abundant molecule present in all living organisms.
All chemical reactions within an organism take place in the presence of ________________.
Several characteristics unique to water contribute to its vital importance in the processes of life, such as its
properties as a ___________________________ and tendency to form ions.
Water as a Solvent
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________________________ is a homogeneous mixture of molecules (Evenly distributed mixture)
Example: Kool-Aid
Parts of a solution:
_____________________: Substances that dissolves other molecules.
Water
____________________: Substance that is being dissolved
Kool-aid
The hydrogen bonds that hold water molecules make water a versatile solvent that can form a solutions with
a__________________(hydrophilic: a molecule that is attracted to water) molecules. Water can form solutions
with ____________________ (hydrophobic: a molecule that repelled from water) molecules.
Example: In an aqueous solution of NaCl and water, the solvent is water and the solute is NaCl. NaCl is ionic, and
therefore hydrophilic and forms an aqueous solution in which water is the solvent and NaCl is the solute. Oil
nonpolar, and therefore hydrophobic. Oil will not dissolve in water.
Water ionization
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Water molecules spontaneously _____________________, or break down, into hydroxide ion (OH-) and
hydrogen ions (H+).
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Chemical equation illustrates the explanation:
H2O
OH- + H+
pH scale
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Ranges 0 to 14, expresses the concentration of __________________________________ ions in a solution.
This determines if a solution is Neutral, Acidic, or Basic
__________________________ Solution: Have equal number of –OH and H+ ions in the solution – pH of 7
___________________________ Solution: have a greater concentration of H+ ions in the solution – pH of less
than 7
____________________ Solution: have a greater concentration of –OH –pH of greater than 7
A________________________ solution : a solution containing either a weak acid and a conjugate base or a
weak base and a conjugate acid, used to stabilize the pH of a liquid upon dilution.
Buffers are substances that ________________________________ of acids and bases on the pH of a solution
Calculating pH
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The pH of a given solution expresses the ______________________ logarithm of the hydrogen ion
concentration
Equation:
pH = -log [H+]
Isomers
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Are organic compounds that have the same molecular formula but _____________________________
There are three types
o ________________________Isomers: differ in their covalent arrangement
o ________________________ isomers: differ in their spatial arrangement around a double bond
o _________________________ or optical isomers: are mirror images of each other
Reactions
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There are five types of reactions you should know for this exam:
1-__________________________ reaction: a reaction that breaks down compounds by the addition of H2O
2- __________________________ synthesis reaction: A reaction in which two compounds are brought together
with H2O released as a product.
3-__________________________ Reaction: A reaction that requires input of energy to occur
A + B + energy  C
4- __________________________ Reaction: A reaction that gives off energy as a product.
A + B  energy + C
5- _______________________ reaction: A reaction involving the transfer of electrons
Biological Macromolecules
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Compounds that contains __________________________ and usually _______________________.
Four types of macromolecules
Nucleic Acid
Proteins
Carbohydrate
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Lipds
Most biological macromolecules are _________________________, which are long chains composed of many
_______________________, similarly structured subunits bonded together
Nucleic Acid
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Form polymers of nucleotides, molecules composed of a ________________________ group, a five-carbon
________________________, and a nitrogenous bases (Four nitrogenouos bases: adenine, guanine, cytosine,
thymine, uracil)
DNA and RNA are nucleic acids that function in ______________________ synthesis and the storage and
transmission of genetic transmission
Proteins
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___________________consist of one or more polypeptides, polymers of ________________________ (building
blocks of proteins) folded into complex 3-D shapes.
An amino acid is a small molecule made up of a central carbon atom, an amino group, a carboxyl group, a
hydrogen atom, and functional group labled “_____________”
___________________ different amino acids exist, each formed with a different R group.
____________________________ form when amino acids bond together in long chains.
The twenty different amino acids can produce a diverse range of proteins, including ____________________,
hormones, cell receptors, antibodies, transport proteins, storage proteins, motor proteins, and structural
proteins.
All ___________________________have either 3 or 4 structural levels
_________________________ Structure: Refers to the sequence of amino acids that form the polypeptides
Hydrogen bonds single groups in a polypeptide chain result in a folded region referred as the secondary
structure. ______________________________ structure includes helices (coils) and sheets (pleated folds)
____________________________ structure describes the folding of an entire polypeptide chain. Interactions
between the _________ groups of the polypeptide chain determine the overall shape of the tertiary structure.
_____________________________ structure: Interactions between two or more polypeptides
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Enzymes
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Are proteins that act as ______________________________
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__________________________: speeds up reactions by lowering the activation energy needed for the reaction
to take place but are not used in the reaction.
__________________________: substance that enzymes act on
Enzymes are selective; they interact only with particular substrates. It is the shape of the enzyme that provide
the_____________________________.
___________________________: The part of the enzyme that interacts with the substrate
Induced-fit model
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Of the ____________________________ interaction describes the active site of an enzyme as specific for a
particular substrate that fist its shape (Often times called the _____________________________ model)
Every enzyme____________________________ (reaction taking place)
o _______________________________
o pH
o Concentration of______________________
o Concentration of the enzyme involved
Competitive and Noncompetitive Inhibition
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________________________ Inhibition: an inhibitor molecule resembling the substrate binds to the active site and
physically blocks the substrate from attaching.
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______________________ inhibition: an inhibitor molecule binds to a different part of an enzyme, causing change
in the shape of the active site so that it can no longer interact with the substrate
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Carbohydrates
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Macromolecule that contains ____________________________________________
Ratio of _____________________
Provides ________________for organisms
Monosaccharides
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Simple sugar or simple ________________________________
Examples: ________________________ (used for cellular respiration), fructose, and lactose – provides
______________________for cells
Disaccharides
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Sugar consisting of two ____________________________ bound together
___________________: Table sugar
o Major sugar in plants
o Fructose and glucose bonded together
______________________
o Found in diary products
o 2 glucose molecules bonded together
Polysaccharides
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Carbohydrate of bonding _______________________________ monosaccharide molecules
Two important molecules for ______________________ are:
o __________________ : Made up of solely of glucose
 Energy storage for plants
 Corn, Potatoes, Beans
o __________________: linking many glucose molecules together
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 Animals store their energy
 Found in liver and muscle cells
Two important structural polysaccharides
o __________________________: composed of glucose molecules
 Used for in the formation of the their cell walls
o ___________________: Important part of the exoskeletons of arthropods– such as insects, lobsters, and
crabs
Lipids
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Organic compounds used by cells as long-term ___________________________ or building blocks
_________________________and insoluble in water because they contain a hydrocarbon tail
Fats
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Which are lipids made up of combining _________________________and three _________________________
o Used as _________________________________ stores in cells
o Are not easily ______________________ as carbohydrates
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Saturated vs. Unsaturated
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_________________________________: Contain no double bonds (means it can be easily broken)
o Associated with ___________________________ and atherosclerosis
_____________________________: contain one (mono-) or more (poly-) double bonds
Steroids
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Act as chemical _________________________ in an organisms
_____________________________: Component found in cell membranes
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Steroids: the __________________________ hormones
(testosterone, progesterone, and estrogen)
Phospholipids
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Combining a __________________with two _____________________ and a ____________________
Phospholipds are bilayered structures they have both__________________________ tail and__________________
head
Major component of _____________________
Functional Groups
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Commonly found in biological _______________________________
Share the same ________________ properties
Functional
Group
Structural Formula
Class of Compounds
Macromolecule
Amino
Amines
Proteins
Carbonyl
Ketones & aldehydes
Lipids
Carboxyl
Carboxylic acid
Proteins
Hydroxyl
Alcohols
Carbohydrates
Notice the -OH
Phosphate
Phosphate
Nucleic Acids
Sulfhydryl
Thiols
Proteins
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Functional Quiz on: _______________________________