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Atoms and Molecules
• All organisms are composed of energy and matter
• All matter is composed of atoms
• Elements are pure substances that contain only one
type of atom and cannot be separated into simpler
substances.
• Atoms have a central core called the nucleus, which is
composed of protons and neutrons that determine the
atomic mass. The protons of an atom have a positive
charge.
Atoms and Molecules
• Surrounding the nucleus are electrons which
are negatively charged.
• Atoms that have equal numbers of electrons
and protons are neutrally charged.
• Atoms that have gained or lost electrons have
charge and are called ions.
• Ions are very important human physiology and
are involved in the electrical responses
associated with nerve and muscle function.
They are also important in the chemical
reactions needed for life.
Chapter 2 – The Body’s Chemical Makeup
Atoms and Molecules
• Chemical bonding occurs between atoms
through the sharing or transferring of
electrons.
•Ionic bonds occur between oppositely
charged ions and involve a transfer of
electrons.
•Ionic compounds are extremely
strong and solids are high melting
points.
•Ionic compounds dissociate in water
and solutions conduct electricity.
Chapter 2 – The Body’s Chemical Makeup
Atoms and Molecules
•Molecular (or Covalent) bonds occur
between molecules that “share”
electrons.
•Molecular compounds have lower
melting points.
•When placed in solution, molecules
remain intact and do not conduct
electricity.
•Most biochemicals are molecular
compounds.
•Most involve only C, H, N, O, P, S
Chapter 2 – The Body’s Chemical Makeup
Atoms and Molecules
•Hydrogen bonds – weak
intermolecular forces between the
partial positive hydrogen atom and a
very electronegative element (O, N, F)
•These are important bonds in the
human body.
•Hydrogen bonds play an important
role in the shape of complex
molecules such as proteins and
nucleic acids.
Chapter 2 – The Body’s Chemical Makeup
Chemical reactions
•Chemical reactions drive the human
body.
•3 Types of Reactions:
•Synthesis
•Decomposition
•Exchange (we learned these as
single & double replacement
reactions)
•All reactions involve energy. Energy is
either required or released.
•Factors that effect reaction rates.
Chapter 2 – The Body’s Chemical Makeup
Acids and Bases
Acid solutions have a high
hydrogen ion concentration
Base or alkaline solutions
have a low hydrogen ion
concentration
A reaction between an
Arrhenius acid and base will
create a salt and water.
Buffers prevent fluctuations in
pH. Buffers are important in
the human body.
Chapter 2 – The Body’s Chemical Makeup
water
•Water is essential for life and has
specific roles in the body
•Water is a polar covalent moleculecharges are not distributed equally
throughout the molecule.
Chapter 2 – The Body’s Chemical Makeup
water
•Water is required for:
•Stabilizing body temperature- remember heat
capacity of liquid water is 4.18 J/goC (Does
anyone remember the relationship of this to
food calories?)
•Protection - water lubricates and cushions
•Chemical Reactions- water is required for
chemical reactions to take place.
•Transport- soluble substances can be
transported through the body when dissolved.
Chapter 2 – The Body’s Chemical Makeup
Other important inorganic
compounds
•O2 - respiration
•CO2 – photosynthesis
Chapter 2 – The Body’s Chemical Makeup
Organic Compounds
•Carbon covalently bonded to functional
groups of other elements create the
molecules necessary for life.
•Functional groups
•Carboxyl – COOH
•Amino
•Carbonyl
•Methyl
•Phosphate
•Hydroxyl
Chapter 2 – The Body’s Chemical Makeup
Carbohydrates
•Carbohydrates include sugars, starches and
cellulose
•The are the main molecules for energy storage
and energy production
•Some can be used as building materials.
•Monosaccharides – simple sugars
•Glucose, fructose
•Disaccharides – consist of 2 monosaccharide units
•Sucrose, lactose
•Polysaccharides-made of repeating
monosaccharide units linked together by
glycosidic bonds.
•Starch, glycogen, cellulose
Chapter 2 – The Body’s Chemical Makeup
Carbohydrates
Chapter 2 – The Body’s Chemical Makeup
Lipids
•Fats and fat-like substances
•Insoluble in water
•Consist mostly of carbon and hydrogen
(hydrocarbons)
•Functions:
•store energy
•form cell membranes
•building blocks of steroid hormones
•Can be saturated or unsaturated
Chapter 2 – The Body’s Chemical Makeup
Lipids
Chapter 2 – The Body’s Chemical Makeup
Proteins
•Macromolecules that are polymers formed from
amino acid monomers
•great structural diversity
•many functions:
•structure
•enzyme catalysis
•defense
•transport
•motion
Chapter 2 – The Body’s Chemical Makeup
Proteins
Chapter 2 – The Body’s Chemical Makeup
Nucleic Acids
•DNA & RNA
•Transmit hereditary information by determining
what proteins a cell makes
•Made of nucleotide monomers (a ribose or
deoxyribose, a phosphate group(s), and a
nitrogenous base)
Chapter 2 – The Body’s Chemical Makeup
Nucleic Acids
Chapter 2 – The Body’s Chemical Makeup