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Introduction to Biomolecules

Biochemistry: Understanding Living Organisms At the Molecular Level

A major goal of biochemistry is to study the cellular processes of living organisms and how these processes relate to the functioning of the organism. Research in the area of biochemistry has been extremely successful over the last century; we now know the atoms and biomolecules that make up living organisms, the central dogma around which biological information is transferred and how this information results in a greater understanding of ourselves and the world in which we live. One of the most important results from research in biochemistry is that all organisms are uniform at the molecular level and the diversity we see today is a result of evolution.  

What biomolecules make up living organisms?

List of biomolecules in E. coli 

Biomolecules in E. Coli % by Weight Numbers of Types
Water 70% 1
Ions 1% ~20
Amino Acids* 0.4% 20 [including 120 a.a. involved in non protein function
Sugars 3% ~200
Nucleotides 0.4% 5[~200]
Lipids (free) 2% 50
Secondary Compounds 0.2% 250
Proteins* 15% 2000-3000
Polysaccharides 3% ~200
Nucleic Acids RNA= 6%, DNA=1% RNA= 1000, DNA=1
Lipid (membranes) 2% 50
Various (lignins, isoprenoids)    

Highlighted in this table are four major classes of biomolecules. The *polymers of life include proteins, polysaccharides, nucleic acids, and lipids and their corresponding *monomers, amino acids, sugars, nucleotides, and free lipids, respectively. There are also combinations of monomers and polymers such as glycolipids, lipoproteins, etc.

Characteristics of Biomolecules

Handedness (Chirality), Sense, Directionality

Forces that Hold Molecules Together

Covalent Bonds, Hydrogen Bonds, Ionic Bonds, Van Der Waals Forces, Hydrophobic Interactions

Weak Forces

Stability and Flexibility, Structural Complementarity, Recognition, Complexes (especially Van Der Waals), Limited Environmental Tolerances


implied in any changes in the forces/bonds that are holding molecules together- stability

synthesis, polymerization of biomolecules (metabolism) imply energy transformations

Decay, turnover (related to entropy)

Other transformations (e.g., light ---> chemical instability)


Implied by synthesis, decay—chemical reactions, limited by activation energy structural basis of enzyme catalysis, measurement, and organization of catalyzed sequential reactions are the major foci of the course


Course considers biomolecules—proteins, sugars, lipids—and transformations among them (metabolism), with emphasis on proteins (enzymes) and their role in catalyzing metabolic reactions 

Energy is important: distinguish between binding energy, energy transformations, etc. (nucleic acids are treated in BIS 101; complex cell activities in BIS 104)