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Basic Energy Concepts
Types of Catabolism
Feremented Foods
Catabolism of Fats
Catabolism of Proteins
Amazing Respirations
Membranes and
Energy Generation

Anaerobic Respiration
Summary of Catabolism
Collecting Elements
Synthesizing Monomers
Carbon Assimilation
Nitrogen Assimulation
Other Assimilation
Formation of
Amino Acids

Lipid Synthesis
Nucleotide Synthesis
Making Polymers
Structural Assembly
Amphibolic Pathways

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©2000 Timothy Paustian, University of Wisconsin-Madison

From studying microbial growth and nutrition it is possible to determine what microbes can use as nutrients and what structures they make from those nutrients. But how do they convert those food sources to more cells? The intense study of microorganisms in the last 130 years has revealed many of the details about how they do business. In this section we take advantage of that body of knowledge and dive deep into the lower levels of metabolism to gain an understanding at the molecular level. We will learn how a cell takes nutrients from the environment and uses them to produce energy and reducing power. This stored energy is then put to work making various cell structures - membranes, cell walls, proteins and nucleic acids.

To start on the road to understanding metabolism, you first have to know what it means. So, some definitions.


The sum total of all reactions which occur in a cell. Metabolism consists of two types of processes catabolism and anabolism.


How complex molecules are broken down into smaller, simpler, molecules with the release of energy and reducing power (electrons). This definition is simplistic - not all energy generating processes in bacteria involve the break down of larger molecules.


Synthesis of complex molecules from simpler ones to form cell structures, this requires energy and often reducing power.

Organization of this chapter

The discussion of metabolism begins with a review of some important thermodynamic and chemical concepts that guide how microbes (and all living things) do business. A short introduction into the important machinery in cellular processes comes next. Then, we look at catabolism discussing some "classic" pathways that are used by a large number of microorganisms. "Next fermentation" and respiration are touched upon during this discussion and some interesting examples of each are described. Bacterial Photosynthesis is briefly mentioned (there is a whole chapter devoted to just that) and we finish up with a section on Anabolism

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