Transcript Ch 2 Chemistry - My Teacher Pages

Chemistry Ch 2
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The “stuff” of the universe
Anything that has mass and takes up space
States of matter
–
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Solid – has definite shape and volume
Liquid – has definite volume, changeable shape
Gas – has changeable shape and volume
Matter And Energy
Graphite —
layer
structure of
carbon
atoms
reflects
physical
properties.
A Chemist’s View of
Water
Macroscopic
H 2O
(gas, liquid, solid)
Particulate
Symbolic
STATES OF MATTER
_______ — have rigid shape, fixed
volume. External shape can reflect the
atomic and molecular arrangement.
– Reasonably well understood.
 _______ — have no fixed shape and
may not fill a container completely.
– Not well understood.
 _______ — expand to fill their container.
– Good theoretical understanding.
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OTHER STATES OF
MATTER
 PLASMA — an electrically charged
gas; Example: the sun or any other
star
 BOSE-EINSTEIN
CONDENSATE — a condensate
that forms near absolute zero that
has superconductive properties;
Example: supercooled Rb gas
Energy
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The capacity to do work (put matter into
motion)
Types of energy
–
–
Kinetic – energy in action
Potential – energy of position; stored (inactive)
energy
Kinetic and Potential Energy
Forms of Energy
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Chemical – stored in the bonds of chemical
substances
Electrical – results from the movement of charged
particles
Mechanical – directly involved in moving matter
Radiant or electromagnetic – energy traveling in
waves (i.e., visible light, ultraviolet light, and
X rays)
Forms of Energy
Endergonic and Exergonic Reactions
Composition of Matter
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Elements – unique
substances that cannot
be broken down by
ordinary chemical
means
Atoms – more-or-less
identical building blocks
for each element
Atomic symbol – oneor two-letter chemical
shorthand for each
Atoms and Elements
Properties of Elements
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Each element has unique physical and
chemical properties
–
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Physical properties – those detected with our
senses
Chemical properties – pertain to the way atoms
interact with one another
Physical
Properties
What are some
physical properties?
 color
 melting and boiling
point
 odor
Physical Changes
can be observed without
changing the identity of
the substance
Some physical changes would
be
 boiling of a liquid
 melting of a solid
 dissolving a solid in a liquid to
give a homogeneous mixture
— a SOLUTION.
–
A Chemist’s View
Macroscopic
Particulate
2 H2(g) + O2 (g)
--> 2 H2O(g)
Symbolic
Chemical Properties and
Chemical Change
•Burning hydrogen (H2) in
oxygen (O2) gives H2O.
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Chemical change or chemical
reaction — transformation of
one or more atoms or
molecules into one or more
different molecules.
Sure Signs of a Chemical
Change
 Heat
 Light
 Gas
Produced
(not from boiling!)
 Precipitate – a
solid formed by
mixing two liquids
together
Physical vs. Chemical
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Examples:
–
melting point
physical
–
flammable
chemical
–
density
physical
–
magnetic
physical
–
tarnishes in air
chemical
Physical vs. Chemical
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Examples:
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rusting iron
–
dissolving in water
–
burning a log
–
melting ice
–
grinding spices
Major Elements of the Body
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Oxygen (O)
Carbon (C)
Hydrogen (H)
Nitrogen (N)
Lesser and Trace Elements of the
Human Body
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Lesser elements make up 3.9% of the body and
include:
–
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Calcium (Ca), phosphorus (P), potassium (K), sulfur (S),
sodium (Na), chlorine (Cl), magnesium (Mg), iodine (I), and
iron (Fe)
Trace elements make up less than 0.01% of the
body
–
They are required in minute amounts, and are found as part
of enzymes
Atomic Structure
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The nucleus consists of neutrons and protons
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Neutrons – have no charge and a mass of one atomic mass
unit (amu)
Protons – have a positive charge and a mass of
1 amu
Electrons are found orbiting the nucleus
–
Electrons – have a negative charge and 1/2000 the mass of
a proton (0 amu)
Models of the Atom
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Planetary Model – electrons move around
the nucleus in fixed, circular orbits
Orbital Model – regions around the nucleus
in which electrons are most likely to be found
Identification of Elements
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Atomic number – equal to the number of protons
Mass number – equal to the mass of the protons and
neutrons
Atomic weight – average of the mass numbers of all
isotopes
Isotope – atoms with same number of protons but a
different number of neutrons
Radioisotopes – atoms that undergo spontaneous
decay called radioactivity
Radiotherapy
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Rapidly dividing cells are particularly sensitive to
damage by radiation. For this reason, some
cancerous growths can be controlled or eliminated
by irradiating the area containing the growth.
External irradiation can be carried out using a
gamma beam from a radioactive cobalt-60 source,
though in developed countries the much more
versatile linear accelerators are now being utilized as
a high-energy x-ray source (gamma and x-rays are
much the same).
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Internal radiotherapy is by administering or planting a small
radiation source, usually a gamma or beta emitter, in the target
area. Iodine-131 is commonly used to treat thyroid cancer,
probably the most successful kind of cancer treatment. It is also
used to treat non-malignant thyroid disorders. Iridium-192
implants are used especially in the head and breast. They are
produced in wire form and are introduced through a catheter to
the target area. After administering the correct dose, the implant
wire is removed to shielded storage. This brachytherapy (shortrange) procedure gives less overall radiation to the body, is
more localized to the target tumor and is cost effective.
Molecules and Compounds
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Molecule – two or more atoms held together
by chemical bonds
Compound – two or more different kinds of
atoms chemically bonded together
Molecules
The Nature of Matter
Gold
Mercury
Chemists are interested in the nature of
matter and how this is related to its atoms
and molecules.
Mixtures and Solutions
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Mixtures – two or more components physically
intermixed (not chemically bonded)
Solutions – homogeneous mixtures of components
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Solvent – substance present in greatest amount
Solute – substance(s) present in smaller amounts
Types of Mixtures
 Variable
combination of 2 or more
pure substances.
Heterogeneous –
visibly separate phases
Homogeneous –
Same throughout
Concentration of Solutions
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Percent, or parts per 100 parts
Molarity, or moles per liter (M)
A mole of an element or compound is equal
to its atomic or molecular weight (sum of
atomic weights) in grams
Colloids and Suspensions
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Colloids, or emulsions, are heterogeneous
mixtures whose solutes do not settle out
Suspensions are heterogeneous mixtures
with visible solutes that tend to settle out
Mixtures Compared with Compounds
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No chemical bonding takes place in mixtures
Most mixtures can be separated by physical
means
Mixtures can be heterogeneous or
homogeneous
Compounds cannot be separated by physical
means
All compounds are homogeneous
Chemical Bonds
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Electron shells, or energy levels, surround the
nucleus of an atom
Bonds are formed using the electrons in the
outermost energy level
Valence shell – outermost energy level containing
chemically active electrons
Octet rule – except for the first shell which is full with
two electrons, atoms interact in a manner to have
eight electrons in their valence shell
Chemically Inert Elements
Inert elements have their outermost energy level fully occupied
by electrons
Chemically Reactive Elements
Reactive elements do not have their
outermost energy level fully occupied by
electrons
Types of Chemical Bonds
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Ionic
Covalent
Hydrogen
Ionic Bonds
Ions are charged atoms resulting from the
gain or loss of electrons
 Anions have gained one or more electrons
 Cations have lost one or more electrons
Formation of an Ionic Bond
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Ionic bonds form between atoms by the
transfer of one or more electrons
Ionic compounds form crystals instead of
individual molecules
Example: NaCl (sodium chloride)
Formation of an Ionic Bond
Formation of an Ionic Bond
Covalent Bonds
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Covalent bonds are formed by the sharing of
two or more electrons
Electron sharing produces molecules
Single Covlent Bonds
Double Covlalent Bonds
Triple Covalent Bonds
Polar and Nonpolar Molecules
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Electrons shared equally between atoms
produce nonpolar molecules
Unequal sharing of electrons produces polar
molecules
Atoms with six or seven valence shell
electrons are electronegative
Atoms with one or two valence shell
electrons are electropositive
Comparison of Ionic, Polar Covalent,
and Nonpolar Covalent Bonds
Hydrogen Bonds
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Too weak to bind atoms together
Common in dipoles such as water
Responsible for surface tension in water
Important as intramolecular bonds, giving the
molecule a three-dimensional shape
Hydrogen Bonds
Chemical Reactions
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Occur when chemical bonds are formed,
rearranged, or broken
Are written in symbolic form using chemical
equations
Chemical equations contain:
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Number and type of reacting substances, and
products produced
Relative amounts of reactants and products
Examples of Chemical Reactions
Patterns of Chemical Reactions
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Combination reactions: Synthesis reactions which
always involve bond formation
A + B  AB
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Decomposition reactions: Molecules are broken
down into smaller molecules
AB  A + B
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Exchange reactions: Bonds are both made and
broken
AB + C  AC + B
Oxidation-Reduction (Redox)
Reactions
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Reactants losing electrons are electron
donors and are oxidized
Reactants taking up electrons are electron
acceptors and become reduced
Energy Flow in Chemical Reactions
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Exergonic reactions – reactions that release
energy
Endergonic reactions – reactions whose
products contain more potential energy than
did its reactants
Reversibility in Chemical Reactions
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All chemical reactions are theoretically
reversible
A + B  AB
AB  A + B
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If neither a forward nor reverse reaction is
dominant, chemical equilibrium is reached
Factors Influencing Rate of Chemical
Reactions
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Temperature – chemical reactions proceed quicker
at higher temperatures
Particle size – the smaller the particle the faster the
chemical reaction
Concentration – higher reacting particle
concentrations produce faster reactions
Catalysts – increase the rate of a reaction without
being chemically changed
Enzymes – biological catalysts
Biochemistry
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Organic compounds
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Contain carbon, are covalently bonded, and are
often large
Inorganic compounds
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Do not contain carbon
Water, salts, and many acids and bases
Properties of Water
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High heat capacity – absorbs
and releases large amounts of
heat before changing
temperature
High heat of vaporization –
changing from a liquid to a gas
requires large amounts of heat
Polar solvent properties –
dissolves ionic substances,
forms hydration layers around
large charged molecules, and
serves as the body’s major
transport medium
Properties of Water
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Reactivity – is an
important part of
hydrolysis and
dehydration synthesis
reactions
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Cushioning – resilient
cushion around certain
body organs
Surface tension
Salts
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Inorganic compounds
Contain cations other than H+ and anions
other than OH–
Are electrolytes; they conduct electrical
currents
Acids and Bases
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Acids release H+ and are therefore proton
donors
HCl  H+ + Cl –
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Bases release OH– and are proton acceptors
NaOH  Na+ + OH–
Acid-Base Concentration (pH)
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Acidic solutions have higher H+ concentration
and therefore a lower pH
Alkaline solutions have lower H+
concentration and therefore a higher pH
Neutral solutions have equal H+ and OH–
concentrations
Acids and Bases Video
Acid-Base Concentration (pH)
Acidic: pH 0–6.99
Basic: pH 7.01–14
Neutral: pH 7.00
pH Scale Video
Buffers
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Systems that resist abrupt and large swings
in the pH of body fluids
Carbonic acid-bicarbonate system
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Carbonic acid dissociates, reversibly releasing
bicarbonate ions and protons
The chemical equilibrium between carbonic acid
and bicarbonate resists pH changes in the blood
Organic Compounds
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Molecules unique to living systems contain
carbon and hence are organic compounds
They include:
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Carbohydrates
Lipids
Proteins
Nucleic Acids
Carbohydrates
Carbohydrates
Contain carbon, hydrogen, and oxygen
Their major function is to supply a source
of cellular food
Examples:
Monosaccharides or simple sugars
Carbohydrate Video
Carbohydrates
Disaccharides or double sugars
Carbohydrates
Polysaccharides or polymers of simple sugars
Lipids
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Contain C, H, and O, but the
proportion of oxygen in lipids
is less than in carbohydrates
Examples:
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Neutral fats or triglycerides
Phospholipids
Steroids
Eicosanoids
Neutral Fats (Triglycerides)
Composed of three fatty acids bonded to a glycerol molecule
Lipids Video
Other Lipids
Phospholipids – modified triglycerides with two fatty acid groups and
a phosphorus group
Other Lipids
Steroids – flat molecules with four interlocking hydrocarbon rings
Eicosanoids – 20-carbon fatty acids found in cell membranes
Representative Lipids Found in
the Body
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Neutral fats – found in subcutaneous tissue and around
organs
Phospholipids – chief component of cell membranes
Steroids – cholesterol, bile salts, vitamin D, sex hormones,
and adrenal cortical hormones
Fat-soluble vitamins – vitamins A, E, and K
Eicosanoids – prostaglandins, leukotriens, and
thromboxanes
Lipoproteins – transport fatty acids and cholesterol in the
bloodstream
Amino Acids
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Building blocks of protein, containing an
amino group and a carboxyl group
Amino acid structure
Amino Acids
Protein Video
Protein
Macromolecules composed of combinations of 20 types of amino
acids bound together with peptide bonds
Structural Levels of Proteins
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Primary – amino acid
sequence
Secondary – alpha
helices or beta pleated
sheets
Structural Levels of Proteins
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Tertiary –
superimposed folding of
secondary structures
Quaternary –
polypeptide chains
linked together in a
specific manner
Fibrous and Globular Proteins
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Fibrous proteins
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Extended and strandlike proteins
Examples: keratin, elastin, collagen, and certain contractile
fibers
Globular proteins
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Compact, spherical proteins with tertiary and quaternary
structures
Examples: antibodies, hormones, and enzymes
What Are Enzymes?
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Most enzymes are
Proteins (tertiary and
quaternary
structures)
Act as Catalyst to
accelerates a reaction
Not permanently
changed in the
process
Enzymes
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Are specific for
what they will
catalyze
Are Reusable
End in –ase
-Sucrase
-Lactase
-Maltase
How do enzymes Work?
Enzymes work
by weakening
bonds which
lowers
activation
energy
Enzymes
Without Enzyme
With Enzyme
Free
Energy
Free energy of activation
Reactants
Products
Progress of the reaction
Enzyme-Substrate Complex
The substance (reactant) an enzyme acts
on is the substrate
Substrate
Joins
Enzyme
Induced Fit
A change in the shape of an enzyme’s
active site
Induced by the substrate
Protein Denuaturation
Reversible unfolding of proteins due to
drops in pH and/or increased temperature
Protein Denuaturation
Irreversibly denatured proteins cannot refold and are formed by
extreme pH or temperature changes
Factors Affecting Enzyme Activity
 Temperature
 pH
 Cofactors
 Inhibitors
& Coenzymes
Temperature & pH
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High temperatures are the most
dangerous reactions & denature enzymes
(Most like normal Body temperatures)
Most enzymes like near neutral pH (6 to
8)
Denatured (unfolded) by ionic salts
Cofactors and Coenzymes
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Inorganic substances (zinc, iron) and
vitamins (respectively) are sometimes
need for proper enzymatic activity.
Example:
Iron must be present in the
quaternary structure of hemoglobin
in order for it to
pick up oxygen.
Two examples of Enzyme
Inhibitors
a. Competitive inhibitors: are
chemicals that resemble an
enzyme’s normal substrate
and compete with it for the
active site.
Substrate
Enzyme
Inhibitors
Noncompetitive inhibitors:
Inhibitors that do not enter the active
site, but bind to another part of the enzyme
causing the enzyme to change its shape, which
in turn
alters the active site.
Substrate
Enzyme
Noncompetitive
Inhibitor
Molecular Chaperones (Chaperonins)
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Help other proteins to achieve their functional
three-dimensional shape
Maintain folding integrity
Assist in translocation of proteins across
membranes
Promote the breakdown of damaged or
denatured proteins
Characteristics of Enzymes
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Most are globular proteins that act as biological
catalysts
Holoenzymes consist of an apoenzyme (protein) and
a cofactor (usually an ion)
Enzymes are chemically specific
Frequently named for the type of reaction they
catalyze
Enzyme names usually end in -ase
Lower activation energy
Characteristics of Enzymes
Mechanism of Enzyme Action
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Enzyme binds with substrate
Product is formed at a lower activation
energy
Product is released
Mechanism of Enzyme Action
Nucleic Acids
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Composed of carbon, oxygen,
hydrogen, nitrogen, and
phosphorus
Their structural unit, the
nucleotide, is composed of Ncontaining base, a pentose
sugar, and a phosphate group
Five nitrogen bases contribute
to nucleotide structure –
adenine (A), guanine (G),
cytosine (C), thymine (T), and
uracil (U)
Two major classes – DNA and
RNA
Nucleic Acid Video
Deoxyribonucleic Acid (DNA)
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Double-stranded helical
molecule found in the
nucleus of the cell
Replicates itself before
the cell divides,
ensuring genetic
continuity
Provides instructions
for protein synthesis
Structure of DNA
Structure of DNA
Ribonucleic Acid (RNA)
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Single-stranded molecule found in both the
nucleus and the cytoplasm of a cell
Uses the nitrogenous base uracil instead of
thymine
Three varieties of RNA: messenger RNA,
transfer RNA, and ribosomal RNA
Adenosine Triphosphate (ATP)
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Source of immediately usable energy for the
cell
Adenine-containing RNA nucleotide with
three phosphate groups
Adenosine Triphosphate (ATP)
How ATP Drives Cellular Work