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8/2/2019 Chapter 2 Anatomy Lect Notes
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PowerPointLecture Slidesprepared byJanice Meeking,Mount Royal College
C H A P T E R
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2
ChemistryComes Alive:Part A
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Matter
Anything that has mass and occupies space
States of matter:
1. Soliddefinite shape and volume
2. Liquiddefinite volume, changeable shape
3. Gaschangeable shape and volume
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Energy
Capacity to do work or put matter into motion
Types of energy:
Kineticenergy in action
Potentialstored (inactive) energy
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Forms of Energy
Chemical energystored in bonds ofchemical substances
Electrical energyresults from movement ofcharged particles
Mechanical energydirectly involved inmoving matter
Radiant or electromagnetic energyexhibitswavelike properties (i.e., visible light,ultraviolet light, and X-rays)
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Energy Form Conversions
Energy may be converted from one form toanother
Conversion is inefficient because someenergy is lost as heat
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Composition of Matter
Elements
Cannot be broken down by ordinary chemical means
Each has unique properties:
Physical properties
Are detectable with our senses, or aremeasurable
Chemical properties
How atoms interact (bond) with one another
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Composition of Matter
Atoms
Unique building blocks for each element
Atomic symbol: one- or two-letter chemical
shorthand for each element
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Major Elements of the Human Body
Oxygen (O)
Carbon (C)
Hydrogen (H)
Nitrogen (N)
About 96% of body mass
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Lesser Elements of the Human Body
About 3.9% of body mass:
Calcium (Ca), phosphorus (P), potassium (K),sulfur (S), sodium (Na), chlorine (Cl),magnesium (Mg), iodine (I), and iron (Fe)
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Trace Elements of the Human Body
< 0.01% of body mass:
Part of enzymes, e.g., chromium (Cr),
manganese (Mn), and zinc (Zn)
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Atomic Structure
Determined by numbers of subatomicparticles
Nucleus consists of neutrons and protons
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Atomic Structure
Neutrons
No charge
Mass = 1 atomic mass unit (amu)
Protons
Positive charge
Mass = 1 amu
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Atomic Structure
Electrons
Orbit nucleus
Equal in number to protons in atom
Negative charge
1/2000 the mass of a proton (0 amu)
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Models of the Atom
Orbital model: current model used bychemists
Depicts probable regions of greatest electrondensity (an electron cloud)
Useful for predicting chemical behavior ofatoms
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Models of the Atom
Planetary modeloversimplified, outdated
model
Incorrectly depicts fixed circular electron paths
Useful for illustrations (as in the text)
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Copyright 2010 Pearson Education, Inc. Figure 2.1
(a) Planetary model (b) Orbital model
Helium atom
2 protons (p+)2 neutrons (n0)2 electrons (e)
Helium atom
2 protons (p+)2 neutrons (n0)2 electrons (e)
Nucleus Nucleus
Proton Neutron Electroncloud
Electron
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Identifying Elements
Atoms of different elements contain differentnumbers of subatomic particles
Compare hydrogen, helium and lithium (nextslide)
Copyright 2010 Pearson Education, Inc. Figure 2.2
Proton
Neutron
Electron
Helium (He)(2p+; 2n0; 2e)
Lithium (Li)(3p+; 4n0; 3e)
Hydrogen (H)(1p+; 0n0; 1e)
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Identifying Elements
Atomic number = number of protons innucleus
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Identifying Elements
Mass number = mass of the protons andneutrons
Mass numbers of atoms of an element are notall identical
Isotopes are structural variations of elementsthat differ in the number of neutrons they
contain
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Identifying Elements
Atomic weight = average of mass numbers of
all isotopes
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Copyright 2010 Pearson Education, Inc. Figure 2.3
Proton
Neutron
Electron
Deuterium (2H)(1p+; 1n0; 1e)
Tritium (3H)(1p+; 2n0; 1e)
Hydrogen (1H)(1p+; 0n0; 1e)
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Radioisotopes
Spontaneous decay (radioactivity)
Similar chemistry to stable isotopes
Can be detected with scanners
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Radioisotopes
Valuable tools for biological research and
medicine
Cause damage to living tissue:
Useful against localized cancers
Radon from uranium decay causes lungcancer
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Molecules and Compounds
Most atoms combine chemically with otheratoms to form molecules and compounds
Moleculetwo or more atoms bondedtogether (e.g., H2 or C6H12O6)
Compoundtwo or more different kinds ofatoms bonded together (e.g., C6H12O6)
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Mixtures
Most matter exists as mixtures
Two or more components physicallyintermixed
Three types of mixtures
Solutions
Colloids
Suspensions
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Solutions
Homogeneous mixtures
Usually transparent, e.g., atmospheric air orseawater
Solvent
Present in greatest amount, usually a liquid
Solute(s)
Present in smaller amounts
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Concentration of Solutions
Expressed as
Percent, or parts per 100 parts
Milligrams per deciliter (mg/dl)
Molarity, or moles per liter (M)
1 mole = the atomic weight of an element ormolecular weight (sum of atomic weights) ofa compound in grams
1 mole of any substance contains 6.021023molecules (Avogadros number)
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Colloids and Suspensions
Colloids (emulsions)
Heterogeneous translucent mixtures, e.g.,cytosol
Large solute particles that do not settle out
Undergo sol-gel transformations
Suspensions:
Heterogeneous mixtures, e.g., blood
Large visible solutes tend to settle out
Copyright 2010 Pearson Education, Inc. Figure 2.4
Solution
Solute
particles
Solute
particlesSolute
particles
Solute particles are very
tiny, do not settle out or
scatter light.
Colloid
Solute particles are larger
than in a solution and scatter
light; do not settle out.
Suspension
Solute particles are very
large, settle out, and may
scatter light.
ExampleMineral water
ExampleGelatin
ExampleBlood
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Mixtures vs. Compounds
Mixtures
No chemical bonding between components
Can be separated physically, such as bystraining or filtering
Heterogeneous or homogeneous
Compounds
Can be separated only by breaking bonds
All are homogeneous
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Chemical Bonds
Electrons occupy up to seven electron shells(energy levels) around nucleus
Octet rule: Except for the first shell which isfull with two electrons, atoms interact in a
manner to have eight electrons in theiroutermost energy level (valence shell)
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Chemically Inert Elements
Stable and unreactive
Outermost energy level fully occupied orcontains eight electrons
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Copyright 2010 Pearson Education, Inc. Figure 2.5a
Helium (He)(2p+; 2n0; 2e)
Neon (Ne)(10p+; 10n0; 10e)
2e 2e8e
(a) Chemically inert elements
Outermost energy level (valence shell) complete
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Chemically Reactive Elements
Outermost energy level not fully occupied byelectrons
Tend to gain, lose, or share electrons (formbonds) with other atoms to achieve stability
Copyright 2010 Pearson Education, Inc. Figure 2.5b
2e4e
2e8e
1e
(b) Chemically reactive elements
Outermost energy level (valence shell) incomplete
Hydrogen (H)(1p+; 0n0; 1e)
Carbon (C)(6p+; 6n0; 6e)
1e
Oxygen (O)(8p+; 8n0; 8e)
Sodium (Na)(11p+; 12n0; 11e)
2e6e
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Types of Chemical Bonds
Ionic
Covalent
Hydrogen
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Ionic Bonds
Ions are formed by transfer of valence shellelectrons between atoms
Anions ( charge) have gained one or moreelectrons
Cations (+ charge) have lost one or moreelectrons
Attraction of opposite charges results in an
ionic bond
Copyright 2010 Pearson Education, Inc. Figure 2.6a-b
Sodium atom (Na)(11p+; 12n0; 11e)
Chlorine atom (Cl)(17p+; 18n0; 17e)
Sodium ion (Na+) Chloride ion (Cl)Sodium chloride (NaCl)
+
(a) Sodium gains stability by losing one electron, and
chlorine becomes stable by gaining one electron.
(b) After electron transfer, the oppositely
charged ions formed attract each other.
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Formation of an Ionic Bond
Ionic compounds form crystals instead ofindividual molecules
NaCl (sodium chloride)
Copyright 2010 Pearson Education, Inc. Figure 2.6c
CI
Na+
(c) Large numbers of Na+ and Cl ions
associate to form salt (NaCl) crystals.
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Covalent Bonds
Formed by sharing of two or more valence
shell electrons
Allows each atom to fill its valence shell at
least part of the time
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Copyright 2010 Pearson Education, Inc. Figure 2.7a
+
Hydrogenatoms
Carbonatom
Molecule ofmethane gas (CH4)
Structuralformulashowssinglebonds.
(a) Formation of four single covalent bonds:
carbon shares four electron pairs with fourhydrogen atoms.
or
Resulting moleculesReacting atoms
Copyright 2010 Pearson Education, Inc. Figure 2.7b
or
Oxygenatom
Oxygenatom
Molecule ofoxygen gas (O2)
Structuralformulashowsdoublebond.(b) Formation of a double covalent bond: Two
oxygen atoms share two electron pairs.
Resulting moleculesReacting atoms
+
Copyright 2010 Pearson Education, Inc. Figure 2.7c
+ or
Nitrogenatom
Nitrogenatom
Molecule ofnitrogen gas (N2)
Structuralformulashowstriplebond.(c) Formation of a triple covalent bond: Two
nitrogen atoms share three electron pairs.
Resulting moleculesReacting atoms
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Covalent Bonds
Sharing of electrons may be equal or unequal
Equal sharing produces electrically balanced
nonpolar molecules
CO2
Copyright 2010 Pearson Education, Inc. Figure 2.8a
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Covalent Bonds
Unequal sharing by atoms with different
electron-attracting abilities produces polarmolecules
H2O
Atoms with six or seven valence shellelectrons are electronegative, e.g., oxygen
Atoms with one or two valence shellelectrons are electropositive, e.g., sodium
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Copyright 2010 Pearson Education, Inc. Figure 2.8b
Copyright 2010 Pearson Education, Inc. Figure 2.9
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Hydrogen Bonds
Attractive force between electropositive
hydrogen of one molecule and anelectronegative atom of another molecule
Common between dipoles such as water
Also act as intramolecular bonds, holding alarge molecule in a three-dimensional shape
PLAY Animation: Hydrogen Bonds
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(a) The slightly positive ends ( +) of the watermolecules become aligned with the slightly
negative ends ( ) of other water molecules.
+
+
+
+
+
+
Hydrogen bond(indicated bydotted line)
Figure 2.10a
Copyright 2010 Pearson Education, Inc. Figure 2.10b
(b) A water strider can walk on a pond because of the high
surface tension of water, a result of the combined
strength of its hydrogen bonds.
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Chemical Reactions
Occur when chemical bonds are formed,
rearranged, or broken
Represented as chemical equations
Chemical equations contain:
Molecular formula for each reactant andproduct
Relative amounts of reactants and products,which should balance
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Examples of Chemical Equations
H + H H2 (hydrogen gas)
4H + C CH4 (methane)
(reactants) (product)
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Patterns of Chemical Reactions
Synthesis (combination) reactions
Decomposition reactions
Exchange reactions
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Synthesis Reactions
A + B AB
Always involve bond formation
Anabolic
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Copyright 2010 Pearson Education, Inc. Figure 2.11a
Example
Amino acids are joined together toform a protein molecule.
(a) Synthesis reactions
Smaller particles are bonded
together to form larger,more complex molecules.
Amino acidmolecules
Proteinmolecule
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Decomposition Reactions
AB A + B
Reverse synthesis reactions
Involve breaking of bonds
Catabolic
Copyright 2010 Pearson Education, Inc. Figure 2.11b
Example
Glycogen is broken down to releaseglucose units.
Bonds are broken in larger
molecules, resulting in smaller,less complex molecules.
(b) Decomposition reactions
Glucosemolecules
Glycogen
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Exchange Reactions
AB + C AC + B
Also called displacement reactions
Bonds are both made and broken
Copyright 2010 Pearson Education, Inc. Figure 2.11c
Example
ATP transfers its terminal phosphategroup to glucose to form glucose-phosphate.
Bonds are both made and broken
(also called displacement reactions).
(c) Exchange reactions
Glucose Adenosine triphosphate (ATP)
Adenosine diphosphate (ADP)Glucosephosphate
+
+
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Oxidation-Reduction (Redox) Reactions
Decomposition reactions: Reactions in which
fuel is broken down for energy
Also called exchange reactions because
electrons are exchanged or shared differently
Electron donors lose electrons and areoxidized
Electron acceptors receive electrons andbecome reduced
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Chemical Reactions
All chemical reactions are either exergonic orendergonic
Exergonic reactionsrelease energy
Catabolic reactions
Endergonic reactionsproducts contain more
potential energy than did reactants
Anabolic reactions
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Chemical Reactions
All chemical reactions are theoretically reversible
A + B AB
AB A + B
Chemical equilibrium occurs if neither a forward norreverse reaction is dominant
Many biological reactions are essentially irreversibledue to
Energy requirements Removal of products
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Rate of Chemical Reactions
Rate of reaction is influenced by:
temperature rate
particle size rate
concentration of reactant rate
Catalysts: rate without being chemicallychanged
Enzymes are biological catalysts