structure and function of bio- molecules

Structure and function of Biomolecules
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STRUCTURE AND FUNCTION OF BIO-
MOLECULES
Table of contents
1. Introduction 9
2. Proteins 13
o The Amino Acids
o The Peptide bond
o The Protein Conformation
o The secondary structures: α-helix and β-sheet
3. Lipids 25
o Fatty Acids
o Hormones derived from Fatty Acids
o Neutral Fats (complex lipids)
o Other complex lipids
o Micelles – lipid double layers
o Simple Lipids
4. Carbohydrates (saccharides) 32
o Monosaccharides
o The glycosidic bond
o Disaccharides and polysaccharides (Glycanes)
o Glycoaminoglycans
o Glycoproteins
5. Polynucleotides 42
o Polynucleotides
o Ribozymes
o The DNA/RNA molecule
o The genetic code
o Flow of the genetic information
6. Résumé 51
7. Problèmes 60

Structure and function of Biomolecules
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1. INTRODUCTION
The molecules that form the building blocks of living organisms obey the same laws of nature as all
other “chemical molecules”. However, such molecules are different in a sense that they have a
function. They can be seen as highly efficient “tools” and/or “machines” or as dedicated “building
materials”. Certain biomolecules even have the ability to replicate and repair themselves. As far as
we know there are no biomolecules without function. However, in a number of cases this function
is not known. Many biological molecules form complex and highly ordered structures. This order is
maintained using energy from the surrounding. The chemistry of such molecules is nevertheless an
important basis for understanding how biomolecules can fulfill their diverse functions. All biologi-
cal phenomena have a molecular and therefore a chemical basis (Table 1.1).
Table 1.1 Distribution of the most important ele-
ments
Earth (crust) Human body
O 47.0 %
Si 28.0 %
Al 7.9 %
Fe 4.5 %
Ca 3.5 %
Na 2.5 %
K 2.5 %
Mg 2.2 %
Ti 0.46 %
H 0.22 %
C 0.19 %
H 63.0 %
O 25.5 %
C 9.5 %
N 1.4 5
Ca 0.31 %
P 0.22 %
Cl 0.08 5
K 0.06 5
S 0.05 %
Na 0.03 %
Mg 0.01 %
Major elements of the organic materials: O, C, N, H, P, S
• Elements that form stable covalent bonds
• Elements from the middle of the PSE ➨ medium strength electronegativity

Structure and function of Biomolecules
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little tendency to form ions
• Elements from the top of the groups ➨ double bonds possible
light atoms, i.e. strong bonds
Carbon atoms can link to each other and form 3D structures
Ions: Na
+, K+, Mg2+, Ca2+, Cl-
Trace elements: Mn, Fe, Co, Cu, Zn, B, Al, V, Mo, I, Si, Sn, Ni, Cr, F, Se
The number of biological molecules is extremely large. However, the number of building blocks
used to make these molecules is surprisingly small (Table 1.2). The molecules tend to have similar
function in all living organisms. Especially the higher organisms tend to use building blocks de-
rived from food to build their own macromolecules (metabolism).
Table 1.2 Examples of building blocks used in biological molecules.
Components of the nucleic
acids
Some components of lipids
COHH
CH2OH
CH2OH
glycerol

Structure and function of Biomolecules
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A monosaccharide

Structure and function of Biomolecules
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Table 1.3 Typical Biopolymers
Monomers Polymers
AMINO ACIDS (Lysine)
Proteins
Peptide Hormones
Neurotransmitters
Toxic alkaloids
NUCLEOTIDES (Adenin)
Nucleic Acids
ATP
Coenzymes
Neurotransmitters
FATTY ACIDS (Palmitic acid)
Membrane lipids
Fats
Waxes
SUGARS (Glucose)
Cellulose
Starch
Fructose
Mannose
Sucrose
Lactose
The building blocks are used to form typical biopolymers such as proteins (amino acids), polysac-
charides (monosaccharides), DNA/RNA (mononucleotides), and lipids (molecular aggregates) (Ta-
ble 1.3). The function of these biopolymers tends to be the same in all living organisms. In addition,
the basic building blocks can be modified to fulfill other functions. For example, 20 amino acids are
used to build the proteins. Besides those more than 150 amino acids are known, which fulfill other
functions in the living organism. Most of these are chemical descendents of the 20 basic ones. Hy-
brid-biopolymers are also known. Examples are the glycoproteins, which contain either one or sev-
eral polypeptide chains (amino acids) and one or several glycosilation structures (saccharides).