Concepts of Matter and Energy
We shall begin with a pun…
• A neutron walked into a diner and asked,
"How much for a coke?" How did the waiter
reply?
• "For you, no charge."
Matter
• Anything that occupies space and has mass
• 3 states (that we are concerned with)
– Solid – definite shape and volume
– Liquid – definite volume, conform to the shape of
the container they are in
– Gas – neither definite shape nor volume
• Matter can change!
– Physical change – does not alter the basic nature of
the substance
– Chemical change – alter the composition of the
substance
Composition of Matter
• Composed of elements – unique substances
that cannot be broken down into simpler
substances by ordinary chemical methods
• Importance in the body:
– 4 elements make up 96% of our body’s mass
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O – breathing, oxidation reactions that produce ATP
C – primary component of biomolecules
H – ionic, determines pH
N – important in structure of proteins and nucleic acids
Atoms!
• Smallest particle that still retains the properties of the
element
– Protons – positively charged subatomic particle, found in the
nucleus, mass of 1 AMU
– Neutrons – neutral subatomic particle, found in the nucleus,
mass of 1 AMU
– Electrons – negatively charged subatomic particle, found in the
electron cloud; mass is negligible
• Planetary Model – atom is a miniature solar system in
which the protons and neutrons are clustered at the center
of the atom in the nucleus; the electrons orbit the nucleus
like planets orbit the sun in our solar system
• Orbital Model – depicts the general location of electrons
outside the nucleus as a haze of negative charge
Atoms cont’d
• Atomic Number – the number of protons in the
nucleus
• Atomic Mass Number (AMU) – the sum of the
protons and neutrons contained in an atom’s
nucleus
• Atomic Weight – the exact mass of an element
– Isotopes – atoms with different numbers of neutrons
in the nucleus
• Radioisotopes – isotopes that are unstable and tend to
decompose to become more stable
• Radioactivity – process of spontaneous atomic decay
Molecules
• Two or more atoms chemically combined
• Compound: two or more DIFFERENT atoms,
chemically combined form a molecule of a
compound. Molecules are the smallest
particles of a compound that still retain the
properties of that compound
– Compounds have different properties than their
atomic constituents!
• Formed by bonds
Chemical Reactions
• Whenever atoms combine with or dissociate
from other atoms
• Bonds: energy relationship involving
interactions between electrons of reacting
atoms
Types of Bonds
• Ionic Bonds – formed between a metal and a nonmetal; in
an ionic bond, metals donate their electrons to non-metals
resulting in a positive charge on the metal and a negative
charge on the non-metal. The ionic “bond” forms as a
result of the attraction between these opposite charges
• Covalent Bonds – formed between two non-metals; in
covalent bonds electrons are shared
– Polar covalent bond – electrons are shared unequally
– Non-polar covalent bond – electrons are shared equally
– Hydrogen Bonds – weak covalent bond important in
biomolecules. In water, H-bonds are responsible for:
• Polarity
• Surface Tension
• Role in biomolecules
3 Types of Reactions
• Synthesis Reactions
– Occur when two or more atoms or molecules
combine to form a larger, more complex molecule
– Bond formation
– Require energy
– Examples: growth, formation of amino acid chains,
repair of damaged tissues
– A + B  AB
Decomposition Reactions
• Occur when a molecule is broken down into
smaller molecules, atoms, or ions
• Bonds are broken
• Energy is released
• Examples: Digestion, breakdown of glycogen
• AB  A + B
Exchange Reactions
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Involves other two types
Bonds are formed AND broken
A “switch” is made between molecular parts
Example: ATP and Glucose
AB + CD  AD + BC
Biochemistry!
• Inorganic Compounds:
– Lack carbon
– Small, simple
• Organic Compounds:
– Contain carbon
– Biomolecules
• Carbohydrates, Lipids, Proteins, Nucleic Acids
Inorganic Compounds
• Water is the most important inorganic compound
in the body
– High heat capacity (resists changes in temperature)
– Universal solvent (polarity)
– Chemical reactivity (reactions in the body do not
occur unless reactants are dissolved in water)
– Cushioning
• Salts – source of ions in the body
– Electrolytes – substances that conduct an electrical
current in solution
• Acids and Bases
Acids and Bases
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pH – concentration of H+ ions in solution
Acids: proton donors (pH<7)
Bases: proton acceptors (pH>7)
Acid-Base reactions: products are always salt
and water
• Buffers – act to maintain pH stability by taking
up excess hydrogen or hydroxyl ions in the
body
Organic Compounds
• Carbohydrates
– Monosaccharides – simplest sugars; characteristic sweet taste;
predominant source of cellular energy – example is glucose
– Disaccharides – made up of two monosaccharide subunits;
sweet in taste
– Polysaccharides – many monosaccharide subunits; most
complex carbohydrates; example is starch; not sweet in taste
• Lipids
– Triglycerides – fatty acids; made of a glycerol backbone and
three fatty acid tails
– Phospholipids – form membranes within the body; polar,
hydrophyllic head group and a non-polar hydrophobic tail group
– Steroids
• Cholesterol
Organic Compounds Cont’d
• Proteins – carry out most cellular functions
(made of 20 common amino acids)
– Fibrous (structural)
– Globular (functional)
– Enzymes – increase the rate of chemical reaction in
the body
• Nucleic Acids – genetic material
– Made of Nucleotides (contain a phosphate group, a
simple sugar, and a nitrogenous base); Adenine,
Thymine, Cytosine, Guanine, Uracil
– DNA/RNA