1.1 Chemistry in Living Systems
Levels of Organization
The levels of organization in living organisms go from the simplest (atoms) to the most complex
(organisms).
ATOMS→MOLECULES→CELLS→TISSUES→ORGANS→ORGAN SYSTEMS→ORGANISMS
The simplest form of life in this organization is the cell.
Organic vs. Inorganic
The chemical compounds that make up the structures in cells are a mixture of organic compounds
and inorganic compounds. To keep it simple, remember it this way .
Organic compounds always contain carbon and hydrogen (and maybe some other
elements), inorganic compounds do not contain carbon and hydrogen together.
Organic compounds are found in living things, their wastes, and their remains (ie; carbohydrates
(sugars, starches), lipids (fats & waxes), proteins, nucleic acids (DNA & RNA)).
Examples of inorganic compounds : water, carbon dioxide.
The elements (atoms) in organic compounds are held together by covalent bonds, which form as a
result of the sharing of two electrons between two atoms.
Chemical Formulas :
There are two kinds of chemical formulas you should understand.
The "molecular formula", which tells you the number of atoms of each element present in a
compound. (ie; the molecular formula for glucose is C6 H12 O6)
A “structural formula” is like a diagram of the compound. It shows the atoms present and how they
are arranged and bonded together in the compound (ie; the structural formula for glucose is below)
r
e three kinds of chemical for
The molecular formula tells us that there are 6 carbon atoms, 12 hydrogen atoms, & 6 oxygen atoms
in one single glucose molecule.
Notice that if you look at the structural formula & tally up each letter (element) you get the
molecular formula.
Write an explanation of the following key terms:
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isotope
radioisotope
molecule
organic molecule
biochemistry
intramolecular
intermolecular
hydrogen bond
hydrophobic
hydrophilic
ion
functional group.
ANSWERS:
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Isotope
Atoms that have the same number of protons (atomic number) but a different number of
neutrons (atomic mass)
For example, Nitrogen atoms become carbon atoms when 1 proton is substituted for 1
neutron and becomes carbon 14.
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Radioisotope
An unstable isotope which is unstable and will decay (ie; the parent isotope carbon 14 will
convert back to the daughter isotope nitrogen 14 from which it was formed in the first
place).
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Molecule
A substance where 2 or more non-metal atoms are joined together covalently (ie; sharing
electrons). The molecules could be the for an element (ie; hydrogen gas, H2) or a compound
(ie; water, H2O).
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Organic molecule
A carbon based molecule which includes C-C, C=C and C-H bonds. There are 3 classes of
biologically important organic molecules: Carbohydrates, Lipids, Proteins and Nucleic Acids.
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Biochemistry
It is the study of the activity of biologically important organic molecules.
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Intramolecular
The forces (ie: covalent bonds and electronegativity) within a molecule that hold the atoms
together (ie: chemical bonds) in its structural formula. The covalent bonding could result in
polar or non-polar covalent bonds.
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Intermolecular
The forces between 2 molecules to hold the molecules together in its structural formula
(ie: physical bonds).
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Hydrogen bond
The result of polar bonds, it is a weak (ie: physical) bond between an atom with a partial
negative charge (oxygen atoms in water) and an atom with a partial positive charge
(hydrogen atoms in water).
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Hydrophobic
It means non-polar molecules that do not attract nor interact with water because of their
polarity.
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Hydrophilic
It means polar molecules that do attract and interact with water because of their polarity.
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Ion
It is a single atom or a group of atoms that has a positive charge (because it lost an electron)
or a negative charge (because it gained an electron).
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Functional group.
Commonly, it is a group of atoms attached to a molecule that have a unique set of physical
and chemical properties. It is the part of the molecule which chemically reacts with other
molecules to bond the molecules together. The functional groups to know are carboxyl,
hydroxyl, amine and phosphate.