Module 2.1: Metabolism
- Enzymes
• Most metabolic functions in cells rely on enzymes to facilitate the
biochemical reactions. An enzyme is a protein,
... [Show More] or group of proteins, that
catalyze (speed up) chemical reactions. The enzyme is not consumed
during the reaction and can be used repeatedly by the cell. The specificity
and function of some enzymes can also be regulated by a cofactor—a
small chemical component, usually metal ions, that assist enzymes during
the catalysis reactions. Thus, cofactors serve as regulators of chemical
reactions: In the absence of the proper cofactor, enzymes are inactive, while
in its presence enzymes are active.
• In order to produce sufficient levels of energy, microorganisms must break
down complex nutrients into smaller, manageable (and useful) subunits.
Enzymes must break down proteins, lipids, and polysaccharides into their
smaller building-block molecules: proteins into amino acids, fats into
glycerol/fatty acids, and polysaccharides into monosaccharides. In turn,
cells must also be able assemble or build the cellular components required
for survival. Most metabolic processes can be classified as either
catabolism or anabolism.
• Catabolism is the process of breaking down larger molecules into useful
energy sources.
• Anabolism is the building up or biosynthesis of macromolecules (see
Module 1) from smaller molecular units into larger complexes.
• For instance, the anabolic process is often used during growth and repair
phases of the cell. The above processes require a great deal of energy in
order to carry out the required reactions for life. Without enzymes and their
ability to increase the rate of a specific chemical reaction, these reactions
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would take too long and exhaust too much energy. If a cell runs out of
energy before the necessary reactions conclude, it dies.
- Adenosine Triphosphate (ATP)
• The most widely used form of energy in the cells is adenosine
triphosphate, or ATP. If a phosphate group is removed from ATP, it
becomes adenosine diphosphate, or ADP. ATP has energy to donate, while
ADP can accept energy (phosphate group) to become ATP. By donating
available phosphate groups, ATP transfers energy from catabolic (breaking
down) reactions to be used for anabolism (building up). This process of
donating and/or accepting energy is what fuels a cell to carry out the
necessary biochemical reactions for survival.
• How microbes produce ATP, specifically the starting source of electrons,
can also be used as a means to further differentiate and characterize
microorganisms.
- Phototrophs acquire energy from photons of light to generate ATP from
ADP [Show Less]