Transcript Chapter_002.ppt

The Human Body in Health and
Illness, 4th edition
Barbara Herlihy
Chapter 2:
Basic Chemistry
1
Lesson 2-1 Objectives
• Define the terms matter and element.
• List the four elements that compose 96% of
body weight.
• Describe the three components of an atom.
• Describe the role of electrons in the formation
of chemical bonds.
• Differentiate among ionic, covalent, and
hydrogen bonds.
• Explain the differences among electrolytes,
ions, cations, and anions.
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Matter
• Matter: Anything that occupies space and has
weight
• Matter exists in three states.
– Solid
– Liquid
– Gas
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3
Matter: Two Types of Changes
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Elements
• Element: Matter composed of atoms that
have the same number of positive charges in
their nuclei
• Trace elements: Present in tiny amounts;
essential for life
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Elements
(cont’d)
• Four elements make up about 96% of human
body weight.
Oxygen
Carbon
Hydrogen
Nitrogen
65.0%
18.5%
9.5%
3.2%
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Atoms
• Atom: Smallest unit of an element with that
element’s chemical characteristics
• Three subatomic particles
 Protons
 Neutrons
 Electrons
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Atoms (cont’d.)
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Atoms (cont’d.)
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Atoms (cont’d.)
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Atoms (cont’d.)
• Atomic number: The number of protons in the
nucleus
• Atomic mass: Sum of the numbers of protons
and neutrons in the nucleus of an atom
• Isotope: A different form of the same atom;
same atomic number, different atomic mass
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Chemical Bonds
• Chemical bond: The electrical attraction
between atoms
• Three types of chemical bonds
– Covalent
– Hydrogen
– Ionic
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Chemical Bonds (cont’d.)
• Ionic bond: Caused by a transfer of electrons
between atoms
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Chemical Bonds (cont’d.)
• Covalent bond: Involves a sharing of electrons
by the outer shells of the atoms
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Chemical Bonds (cont’d.)
• Hydrogen bond: An intermolecular attraction,
not caused by transfer of electrons or sharing
of electrons by outer shells of the atoms
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15
Ions
• Ions: Atoms or groups of atoms that carry an
electrical charge
• Two types of ions
– Cations: Positively charged
– Anions: Negatively charged
• Electrolytes: Form ions when dissolved in
water
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Common Ions: Cations
Name
Symbol
Function
Cations
Sodium
Na+
Fluid balance; nerve-muscle
function
Calcium
Ca2+
Component of bones and teeth;
blood clotting; muscle
contraction
Iron
Fe2+
Component of hemoglobin
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Common Ions: Cations (cont’d.)
Name
Symbol
Function
Cations (cont’d.)
Hydrogen
H+
Important in acid-base
balance
Potassium
K+
Nerve and muscle function
Ammonium
NH4+
Important in acid-base
regulation
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Common Ions: Anions
Name
Symbol
Function
Anions
Chloride
Cl−
Primary extracellular anion
Bicarbonate
HCO3−
Phosphate
PO43−
Important in acid-base
regulation
Component of bones and teeth;
component of ATP
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19
Electrolytes and Ionization
• When an electrolyte breaks apart in solution,
the electrolyte is said to dissociate or ionize.
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Lesson 2-2 Objectives
• Explain the difference between a molecule
and a compound.
• List five reasons why water is essential to life.
• Explain the role of catalysts and enzymes.
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Lesson 2-2 Objectives (cont’d.)
• Differentiate between an acid and a base.
• Define pH.
• Define energy and describe the role of
adenosine triphosphate (ATP) in energy
transfer.
• Differentiate among mixtures, solutions,
suspensions, colloidal suspensions, and
precipitates.
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Molecules and Compounds
• Molecule: Two
or more atoms
bonded
together
• Compound:
Molecules
formed by
two or more
different atoms
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23
Water: A Vital Substance
•
•
•
•
•
Universal solvent
Temperature regulator
Ideal lubricant
Crucial part of most chemical reactions
Protective mechanism
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Chemical Reactions
• Chemical reaction: The interaction of atoms of
molecules or compounds to form new
chemical combinations
• Catalysts: Chemical substances that speed up
the rate of a chemical reaction
• Enzymes: Proteins that serve as catalysts
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Acids and Bases
• Acid: An electrolyte that dissociates into H+
(hydrogen ion) and an anion
• Base: Substance, often OH- (hydroxyl ion), that
combines with H+ to make a solution less
acidic
• Acids and bases can be strong or weak
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pH Scale
• pH: Unit of measurement
indicating how many
hydrogen ions are in a
solution
• pH scale: Ranges from 0 to
14
• Midpoint of scale: pH 7, or
neutral
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Normal blood pH: 7.35 to 7.45
• Acidosis
– Too many H+ ions
– pH less than 7.35
• Alkalosis
– Too few H+ ions
– pH greater than 7.45
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Energy: Ability to Perform Work
• Six forms of energy
– Mechanical
– Chemical
– Electrical
– Radiant
– Thermal
– Nuclear
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Energy Transfer
• Adenosine triphosphate (ATP): Energy transfer
molecule
• Three parts of ATP
– Base
– Sugar
– Three phosphate groups
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Energy Transfer (cont’d.)
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Energy Transfer (cont’d.)
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Energy Transfer (cont’d.)
• After the food we eat is broken down, energy
is released. This energy is transferred to ATP
so it can be used by the cells of the body.
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Mixtures
• Mixtures: Combinations of two or more
substances that can be separated by ordinary
physical means.
• Example: A sugar-iron mixture can be
separated by a magnet.
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Solutions
• Solutions have two parts that remain evenly
distributed (e.g., normal saline).
– Solute: Substance present in smaller amount; is
the substance being dissolved
– Solvent: Part of solution present in greater
amount; does the dissolving
• Two types of solutions
– Aqueous solutions
– Tinctures
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Suspensions and Precipitates
• Suspensions: Mixtures with relatively large
particles
• Colloidal suspension: Particles remain
suspended within the liquid.
• Precipitates: Solids are formed and fall out of
solution during a chemical reaction.
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