Introduction
Basic Energy Concepts
Enzymes
Types of Catabolism
Fermentation
Feremented Foods
Respiration
Catabolism of Fats
Catabolism of Proteins
Amazing Respirations
Membranes and
Energy Generation
Anaerobic Respiration
Lithotrophs
Photosynthesis
Summary of Catabolism
Anabolism
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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Summary of Anabolism
©2000 Timothy Paustian, University of Wisconsin-Madison
The take home messages from anabolism are...
The reason for doing catabolism is to drive anabolism. One of the reasons cells generate energy is so that they can build more of themselves.
Anabolism costs energy. Biological energy is in the form of ATP, to drive reactions, and NADPH + H+, to supply reducing power.
The macromolecules of the cell are synthesized from only a few simple building block; amino acids, sugars, fatty acids and nucleotides. Throw in a few other catabolic intermediates from glycolysis and the TCA cycle and the cell can synthesize all that it needs. This simplicity makes it much easier to build a cell. Image if every component required unique molecules, it would be much more difficult to make a living.
Cells would rather steal what they need from the environment than make it themselves. If a needed amino acid is available in high enough concentrations, the enzymes needed to synthesize that amino acid will be shut down and the genes coding for them will not be transcribed. This conserves precious energy. Another chapter in this textbook deals with the processes cells use to regulate their metabolism.
In the previous web pages we have looked at catabolism and Anabolism in separate sections. It is important to point out that in the cell, this is not the case. catabolism and anabolism are inexorably intertwined. Many of the intermediates and even some of the enzymes can serve both a catabolic and anabolic role. For example in the TCA cycle, many reactions within this pathway are reversible and a cell can "decide" which way to go depending on its need at that time.
The goal of this section on metabolism has been to give you an introduction to the chemistry involved in generating energy and an understanding of the details of making a cell and earning a living as a microbe. I hope you walk away from this information having a new respect for the elegance of the process and for the versatility of microbial metabolism. I find it amazing that if you think about any chemical reaction that generates energy, you will frequently discover a microbe that takes advantage of it to thrive.
