CHAPTER 5
ESSENTIAL CONCEPTS OF METABOLISM
CHAPTER OVERVIEW
An important characteristic of all living organisms is their ability to produce energy from a wide
variety of foodstuffs and to use this energy to synthesize necessary materials. When it was
discovered that microbes could metabolize a wide variety of materials, many phenomena, such as the
souring of milk, the production of alcohol in fruit juices, and the spoilage of meats, were explained.
These metabolic characteristics of microbes led to other discoveries and ultimately to the use of
microbes for industrial production of a wide variety of chemicals, byproducts, enzymes, and the like.
An understanding of metabolic systems is essential for the development of industrial uses of
microorganisms. This chapter provides an overview of the characteristics of the pathways that
microbes use to accomplish their metabolic activities.
Glycolysis, the Krebs cycle, electron transport, and the chemiosmosis systems are described
and illustrated with examples to show how they are involved in producing some important substances
used in industry, in agriculture, and for human consumption.
The last section explains the importance and relationships of other metabolic processes seen
in environmentally important microbes.
CHAPTER OBJECTIVES












Define:
metabolism, autotrophy, heterotrophy, oxidation, reduction, photoautotrophy, photoheterotrophy,
chemoautotrophy, hemoheterotrophy, glycolysis, fermentation, aerobic metabolism, and
biosynthetic processes
List and describe the characteristics of enzymes and explain how these characteristics contribute
to enzymatic function.
List and describe the characteristics of a coenzyme, noting especially its relationship to an
enzyme.
List the basic steps of the glycolysis pathway, noting especially the location of energy production,
the role of coenzymes, and the significance of pyruvic acid.
List several important characteristics of fermentation.
Describe the Krebs cycle, and explain its significance in energy capture.
Describe the electron transport chain, noting especially the processes of oxidative
phosphorylation and chemiosmosis and their significance in energy capture.
Contrast the metabolic processes of fermentation and aerobic metabolism, noting especially the
cycles involved, energy production, type of oxidation, and the end products.
Describe how microorganisms metabolize fats and proteins for energy.
Briefly describe the process of photosynthesis and explain its significance in photoheterotrophic
and photoautotrophic microbes.
Contrast the processes of photoheterotrophy and chemo-autotrophy.
Describe how bacteria carry out biosynthetic activities and relate these activities to their
amphibolic pathways.
5-1

List and describe several examples of how bacteria use energy for membrane transport and for
movement.
CHAPTER OUTLINE
I.
Metabolism: An Overview
A.
Metabolism
1.
Anabolism
2.
Catabolism
B.
Electron transfer
1.
Oxidation
2.
Reduction
C.
Autotrophy
1.
Photoautotrophy
2.
Chemoautotrophy
D.
Heterotrophy
1.
Photoheterotrophs
2.
Chemoheterotrophs
a.
Glycolysis
b.
Fermentation
c.
Aerobic respiration
E.
Relationship of respiration to photosynthesis
F.
Chemical reactions
1.
Metabolic pathways
2.
Catabolic pathways
3.
Anabolic pathways
II.
Enzymes
A.
General characteristics
B.
Properties of enzymes
1.
Activation energy
2.
Reaction surface
a.
Active site
b.
Substrates
c.
Enzyme-substrate complex
3.
Specificity
4.
Classification of enzymes
5.
Location of action
a. Endoenzymes
b. Exoenzymes
C.
Properties of coenzymes and cofactors
1.
Apoenzymes
2.
Holoenzymes
3.
Coenzymes
a.
NAD
5-2
D.
E.
b.
FAD
4. Cofactors
Enzyme inhibition
1.
Competitive inhibition
2.
Noncompetitive inhibition
3.
Allosteric site
4.
Feedback inhibition
Factors that affect enzyme reactions
1.
Temperature and pH
2.
Concentration
III.
Anaerobic Metabolism: Glycolysis and Fermentation
A.
Glycolysis
1.
Phosphorylation
2.
Breakage of glucose
3.
Role of NAD
4.
Formation of ATP
B.
Fermentation
1.
Homolactic-acid fermentation
2.
Alcoholic fermentation
3.
Other kinds of fermentations
4.
Special diagnostic tests
IV.
Aerobic Metabolism: Respiration
A.
Role of glycolysis
B.
The Krebs cycle
1.
Formation of acetyl-CoA
2.
Removal of hydrogen atoms
3.
Special events
C.
Electron transport and oxidative phosphorylation
1.
Electron transport chain
2.
Oxidative phosphorylation
3.
Chemiosmosis
4.
Anaerobic respiration – a bacterial alternative
D.
Significance of energy capture
V.
Metabolism of Fats And Proteins
A.
Fat metabolism
B.
Protein metabolism
VI.
Other Metabolic Processes
A.
Photoautotrophy
1.
Photosynthesis
a.
Light reactions
b.
Dark reactions
2.
Photosynthetic bacteria
5-3
B.
C.
VII.
3.
Eukaryote comparisons
Photoheterotrophy
Chemoautotrophy
1.
Basic characteristics
2.
Chemolithotrophic bacteria
Uses of Energy
A.
Biosynthetic activities
1.
Amphibolic pathways
2.
Other biosynthetic processes
B.
Membrane transport and movement
1.
Membrane transport
a.
Active transport
b.
Phosphotransferase system
2.
Movement
C.
Bioluminescence
 Web Destinations




http://www.liunet.edu/cwis/bklyn/acadres/facdev/FacultyProjects/WebClass/micro-web/htmlfiles/ChapterC-1.html
Long Island University site covers bacterial metabolism
http://www.people.virginia.edu/~rjh9u/enrgysum.html
Robert J. Huskey site covers glycolysis and the Krebs cycle
http://biotech.icmb.utexas.edu/glycolysis/glycohome.html This site from the University of Texas
provides an interactive link through the process of glycolysis.
http://www.bact.wisc.edu/Microtextbook/TOC.html
On-line microbiology textbook
5-4