Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Download

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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
A . Introduction
 chemistry – science that deals with the composition of
substances and the Changes that take place in their
composition .
 Organic chemistry – chemistry that deals with organic
substances (those that contain carbon and hydrogen )
 Biochemistry—chemistry of living organisms ;
essential for understanding physiology because body
functions involve chemical changes that occur within
cells.
 Matter – anything that has weight (or mass) and takes
up space .It can be solids, liquids , or gases .
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Energy
 Energy – the ability to do work . Potential energy
(PE) is stored energy in matters ; Kinetic energy
(KE) is working energy produced by the motion of
matters .
 Energy occurs in 4 forms in the human body :
chemical , electrical , radiant , and mechanical
energy . chemical energy is the most important
form in terms of actually driving chemical reactions.
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Models of the Atom
Figure 2.1
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Atomic number
(AN) = number
of protons =
number of
electrons
Atomic weight
(AW) = number
of protons +
number of
neutrons
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IONS
 In addition to neutrons , the electrons of atoms tend
to change also – atoms that have either lost or
gained electrons are called ions. Atoms that have
lost electrons (as a result , now contain more p+ than
e-) are called cat ions which carry positive charges ,
while atoms that have gained excessive electrons (as
a result, now contain more e- than p+ ) are called
anions which carry negative charges .
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Chemically Reactive Elements
 Reactive elements
do not have their
outermost energy
level fully occupied
by electrons
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Figure 2.4b
Bonding of atoms
 Ionic bonding = formed by attraction of
opposite charges of a cation and an anion
(e.g. Na+ + Cl- →NaCl).
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Formation of an Ionic Bond
Figure 2.5b
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Covalent bonding
 formed by sharing of electrons between two
atoms (e.g. Cl + Cl →Cl2) . The strongest
type of bonding .
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Hydrogen
bonding
formed by weak attraction between H+ and nitrogen (N) or oxygen
(O) (e.g. H of a water molecule attracting to O of another water
molecule). The weakest type of bonding .
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 Chemical reactions involve the formation , breaking , or
rearrangement of chemical bonds . There are 4 general types :
 Dehydration synthesis : A + B → AB + water
 Decomposition (or hydrolysis) : AB + water → A + B
 Exchange : AB + CD → AD + CB
 Reversible : A + B < - - - > AB
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The rate of chemical reactions is
dependent on 4 factors :
 size of reacting molecules : smaller molecules have greater
kinetic energy which produces faster reaction rate .
 Temperature : higher temperature creates greater kinetic
energy and faster reaction rate .
 Concentration of reactants : higher concentration produces
faster rate .
 Presence of catalysts : inorganic catalysts or organic
catalysts (enzymes) increase reaction rate .
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 Electrolytes = compounds that release ions when
dissolved in water (e.g. NaCl + water → Na+ + Cl- )
 Acids = electrolytes that release H+ (e.g. H2 CO3 → H+ +
HCO3- )
 Bases = electrolytes that release anions that can combine
with H+ (e.g. NaOH → Na+ + OH- )
 Salts = substances formed by the reaction between an
acid and a base (e.g. HCl + NaOH → H2O + NaCl )
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PH
 measurement of H+ concentration in a solution
 - More H+ = lower PH = more acidic
 - Less H+ = higher pH = less acidic
 -Ph scale is form 0 to 14 , where the
midpoint (pH 7.0) is neutral. From pH 0
to 6.9 , it is acid ; while from pH 7.1 to
14 is base .
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PH Scale
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Figure 2.9
 Organic substances = chemicals that
contain C and H (e.g. Carbohydrates or
Protein , Fat, and nucleic acid)
 Inorganic substances = chemicals that do
not contain C and H (e.g. table salt or NaCl ,
carbon dioxides or CO2 , ammonia or NH3 )
 (Most inorganic substances are small,
electrolytes and usually use ionic bonding ,
and most organic substances are large , non
electrolytes, and usually use covalent
bonding ).
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An Organic Compound
(cholestrol)
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Protein
Figure 2.3
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Carbohydrate
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Nucleic Acid
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Solutions and concentration
When a substance is dissolved in a liquid (ex. water) , a solution is
formed . The substance that is dissolved is the solute and the liquid in
which the dissolution occurred is the solvent .
Concentration : The measure of dissolution of a particular solute in a
given volume of solvent . it is measured in molarity .
Molarity : The number of solute molecule per unit volume of solution .
Buffer : A substance that can react with an acid or a base and thus resist a
change in PH .
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Tonicity
 the ability of a solution to change the tone or shape of
cells by changing their internal H2O volume .
 - Hypertonic : solutions with higher osmotic pressure.
cells in a Hypertonic solution lose H2O and shrink .
 - Hypotonic : solution with a lower osmotic pressure –
cells in hyportonic solution gain H2O and swell .
 - Isotonic : same tonicity . cell in isotonic solutions
neither gain , nor lose H2O .
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The effect of solutions of varying tonicities on
red blood cell
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Enzymes
1.Are always made of globular proteins .
2.Can promote the rate of chemical reactions by billions of times.
3.Can lower the activation energy – energy necessary to start a
reaction – resulting in a conservation of energy .
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4. Are usually reusable or recycled .
5. Are always very specific – using its active site , each
enzyme is designed to bind to only one specific substance ,
the substrate and rapidly transforms the substrate into a
product .
6. Many enzymes would not achieve their optimum efficiency
unless they are bound to a cofactor (i.e. ions , metals) or to a
coenzyme (organic cofactors such as vitamins ).
7. Most enzymes' names end with "ase“(ex. Dnase, Sucrase)
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Mechanism of Enzyme Action
Active site
Amino acids
1
Enzyme (E)
Substrates (s)
H20
Enzymesubstrate
complex (E–S)
2
Free enzyme (E)
3
Peptide bond
Internal rearrangements
leading to catalysis
Dipeptide product (P)
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Figure 2.20
 Factors that affect enzyme activity
 Since all enzymes are made of globular proteins ,
and proteins are made of amino acids linked by
peptide bonds , enzymes can be affected or
denatured very easily .
 Factors that could affect or denature enzymes
include heat , ration , electricity , certain chemical
substances , and extreme pH.
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METABOLISM
Anabolic metabolism
Uses dehydration synthesis reaction to build large molecules from
small molecules .
Each reaction releases a water molecule and requires energy input
Example – monosaccharide + energy → polysaccharide + water
amino acids + energy → protein + water.
Synthesis and Hydrolysis of Sucrose :
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 Catabolic metabolism
 Uses hydrolysis (or decomposition) reaction to break up large
molecules into smaller molecules .
 Each reaction requires a water molecule and releases energy .
 Example -- triglyceride + water → fatty acids + energy
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Adenosine Triphosphate (ATP)
 High- energy molecule that is derived from the nucleotide ,
adenine .
 Contains 3 phosphate groups (PO4) and high-energy chemical
bonds that each time the bonds are broken , a large amount of
energy is generated .
 Energy is released by ATP is broken down by hydrolysis reaction
ATP + water → ADP + PO4+ energy [ADP = adenosine
diphosphate ]
 ADP + water → AMP + PO4 + energy
 [AMP = adenosine monophosphate ]
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ATP
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