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Understanding the chemistry of life helps us understand life its self
b
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A molecule contains two or more atoms linked through covalent bonds in a covalent
bond two atoms share a pair of electrons
d
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Water molecules associate with each other through weak attractions known as
hydrogen bonds the unique properties of water have a profound influence on the
chemistry of life
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A chemical reaction occurs when bonds between atoms are formed or broken to sustain
life thousands of different chemical reactions must occur inside even the simplest life
g
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Four main classes of molecules are common to all living organism carbs proteins lipids
and nucleic acids
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a
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1 matter elements and atomic structure
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An atom is the smallest unit of an element that has the chemical properties of
that element atoms contain positively charged protons uncharged neutrons and
negatively charged electrons the number and arrangement of electrons in the
atom of an element determines the chemical properties of the element
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Isotopes of an elements have different numbers of neutrons but sea number of
protons radioisotopes are isotopes that give off radiation
b
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2 the bonds that link atoms
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Covalent bonds are formed by the sharing of electrons between atoms share
electrons with other atoms to fill their outermost electron shells to capacity the
bonding properties of an atom are determined by the number of electrons in its
outermost shell a molecule contains at least two atoms that are held together
by covalent bonds
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d
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3 the special properties of water
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Water is a polar molecule hydrogen bonding between water molecules accounts
for the special properties of water including its high heat capacity and high heat
vaporization properties that enable water to moderate temperature swings
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Water has the highest surface tension of any liquid except mercury surface
tension is a force that tends to minimize the surface are of water at an air water
boundary and it influences many biological phenomena
2
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In chemical reactions bond between atoms are formed or broken although the
participants in a chemical reaction are modified to give rise to ions or molecules
atoms are neither created nor destroyed in the process
ii
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5 the PH scale
i
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acids donate hydrogen ions in a solution bases accept hydrogen ions
ii
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Buffers help maintain a constant PH in an aqueous solution
2
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Carbon atoms can link with each other and with other atoms to generate a great
diversity of compounds
ii
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7 carbohydrates
i
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Carbohydrates provide energy and physical support for living organisms
2
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Amino acids are the building blocks of proteins a chain of amino acids linked
together makes a polypeptide which constitutes the primary structure of a
protein
ii
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9 lipids
i
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Triglycerides are important for energy storage

iii
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Sterols include cholesterol and sex hormones
j
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10 nucleotides and nucleic acids
i
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Nucleotides are the building blocks of the nucleic acids DNA and RNA DNA
polymers made up of four types of nucleotides from the blueprint for life and
govern the anatomical features and chemical reactions of a living organisms
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3
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Biomolecules are those molecules that are unique to living cells
b
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Each unique type of matter is an element; so, there are at least 92 different elements
that occur naturally in the known universe
d
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e
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Negatively charged electrons move around the nucleus in electron shells
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The atomic mass number is the total number of protons and neutrons in an atom
i
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Molecules are two or more atoms that share electrons to form a chemical bond known
as a covalent bond
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An atom becomes a negatively-charged ion when it gains one or more electrons
m
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Salts are held together by ionic bonds
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A chemical formula summarizes the number and type of atoms in a molecule or ionic
compound (salt)
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A hydrogen bond is the weak attraction between a hydrogen atom with a slight positive
charge and a neighboring atom with a slight negative charge
s
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Molecules that do not associate with water (are water-hating) are hydrophobic
u
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When water molecules are heated, they become energetic enough to break their
hydrogen bonds and escape as water vapor in a process called evaporation
w
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Surface tension is a force that tends to minimize the surface area of water at its
boundary with air
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z
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Some macromolecules are polymers, which contain repeating units of small organic
molecules known as monomers
bb
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Glucose is a type of simple sugar called a monosaccharide
dd
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Cellulose strengthens plant cell walls
ff
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Glycogen is a highly-branched polysaccharide that stores energy in animal cells for rapid
release of monosaccharides when energy is needed
hh
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Polypeptides are formed when the amino group of one amino acid is linked to the
carboxyl group of another through a peptide bond
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The alpha helix and beta sheet are two types of local folding
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Denaturation is the destruction of a protein’s three-dimensional shape,
resulting in a loss of protein activity
nn
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Fatty acids in which all the carbon atoms in the hydrophobic chain are linked with a
single covalent bond are called saturated fatty acids
pp
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Three fatty acid molecules bonded to a glycerol molecule make up a triglyceride,
commonly known as a ‘fat’
rr
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When exposed to water, phospholipids form a phospholipid bilayer, with the
hydrophilic heads facing outward and the hydrophobic tails tucked into the interior of
the bilayer
tt
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Cholesterol is a vital component of cell membranes in animals and is the starting
molecule for many other sterols and steroid hormones

vv
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Five different nucleotides make up a class of polymers called nucleic acids
xx
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Trans fats can be found in any foods containing partially hydrogenated oils (even if the
Nutrition Fact label shows ‘O trans fats per serving’)



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