2. Microbial metabolism means series of
biochemical reactions by which a microbe
obtains the energy and nutrients (e.g. carbon) it
needs to live and reproduce.
Catabolism Anabolism
Primary
Metabolism
Secondary
Metabolism
Intermediary
Metabolism
3. Catabolism
• Catabolism is the set of metabolic pathways that breaks down
molecules into smaller units that are either oxidized to release energy.
• Catabolism breaks down large molecules (such as polysaccharides,
lipids, nucleic acids and proteins) into smaller units (such as
monosaccharides, fatty acids, nucleotides, and amino acids,
respectively).
• Cells use the monomers released from breaking down polymers to
either construct new polymer molecules, or degrade the monomers
further to simple waste products, releasing energy.
4. Catabolism
• Cellular wastes include lactic acid, acetic acid, carbon dioxide,
ammonia, and urea. The creation of these wastes is usually an
oxidation process involving a release of chemical free energy, some of
which is lost as heat, but the rest of which is used to drive the synthesis
of adenosine triphosphate (ATP).
• This molecule acts as a way for the cell to transfer the energy released
by catabolism to the energy-requiring reactions that make up
anabolism.
5. Catabolism
• Catabolism therefore provides the chemical
energy necessary for the maintenance and
growth of cells. Examples of catabolic
processes include glycolysis, the citric acid
cycle, the breakdown of muscle protein in
order to use amino acids as substrates for
gluconeogenesis, the breakdown of fat in
adipose tissue to fatty acids, and oxidative
deamination of neurotransmitters by
monoamine oxidase.
6. Anabolism
• Anabolism is the set of metabolic pathways that construct molecules
from smaller units. These reactions require energy, known also as an
endergonic process (absorbing energy in the form of work).
• Anabolism is the building-up aspect of metabolism, whereas catabolism
is the breaking-down aspect. Anabolism is usually synonymous with
biosynthesis.
7. Anabolism
• Anabolism includes the biosynthesis of:
I. Building blocks of cellular macromolecules: e.g. Amino acids,
nucleotides, fatty acids, sugar etc.
II. Vitamins and coenzymes, which are essential for driving various
reactions
III. Cellular macromolecules such as proteins, lipids, nucleic acids,
polysaccharides as well as synthesis of cell structural compounds.
8.
9. PrimaryMetabolism
• Very essential metabolism for cell growth.
• The products of primary metabolism are called as ‘Primary metabolites’.
• It usually performs a physiological function in the organism (i.e. an
intrinsic function). A primary metabolite is typically present in many
organisms or cells.
• Note that primary metabolites do not show any pharmacological actions
or effects.
10. PrimaryMetabolism
• The products of primary metabolism include:
• Energy rich compounds such as ATP, NADP, and others
• Organic acids such as lactic acid, citric acid, acetic acid etc.
• Organic alcohol and solvents such ethanol, glycerol, acetone, butanol
etc.
• Amino acids, Vitamins coenzymes, nucleotides etc.
11. SecondaryMetabolism
• Secondary metabolism (also called specialized metabolism) is a term for
pathways and small molecule products of metabolism that are not
absolutely required for the survival of the organism.
• These molecules are produced by specific cells, that do not need these
metabolites by themselves, but rather can be beneficiary for the whole
organism.
• It is expected that in nature secondary metabolism helps organism to
become more competitive for nutrients with other organisms by either their
ability to obtain and purify necessary nutrients or by killing competitive
organisms.
12. SecondaryMetabolism
• The term secondary metabolite was first coined by Albrecht Kossel, a
1910 Nobel Prize laureate for medicine and physiology in 1910.
• Secondary metabolites also called Specialized Metabolites, secondary
products or Natural Products are organic compounds produced by
bacteria, fungi, or plants which are not directly involved in the normal
growth, development, or reproduction of the organism.
• Bacterial production of secondary metabolites starts in the stationary
phase as a consequence of lack of nutrients or in response to
environmental stress.
13. SecondaryMetabolism
• Secondary metabolite synthesis in. bacteria is not essential for their
growth, however, they allow them to better interact with their ecological
niche.
• E.g. Antibiotic synthesis is the best example which is not essential for
growth but does help organisms to survive against various organisms by
destroying them.
16. Roleofreducing powerinMetabolism
• Reducing power - Many biochemical reactions involve oxidation
(removal of electrons from a compound) & reduction (addition of
electrons to a compound; E. coli stores electrons in coenzymes called
NAD (nicotinamide adenine dinucleotide) & NADP (nicotinamide adenine
dinucleotide phosphate). These compounds capture electrons in the
form of hydrogen atoms from compounds that are being oxidized, thus
forming NADH & NADPH). NAD & NADP stores the cell's reducing
power. Bacteria will then use this reducing power to build its cellular
components (it will reduce other compounds in this process).
17. Roleofreducing powerinMetabolism
• Most of elements exist in oxidized state in nature. Therefore before they
are digested in cell, they must be reduced.
• This requires availability of suitable reducing power.
• NADPH serves as the principle reducing power in all such digestions and
biosynthetic reaction of anabolism.
• Flavin coenzyme FADH2 can also serve as intermediate reducing agent
in biochemical reaction.
18. Generationofreducing power
• Reducing power is generated on oxidation
of a suitable electron donor during
catabolic reactions.
• These electron donor can be either
organic or inorganic molecule.
• NADPH serve as reducing power in most
of biochemical reaction.
• There are several other lesser-known
mechanisms of generating NADPH
19. Generationofreducing power
• NADPH is produced from NADP+. The major source of NADPH in
animals and other non-photosynthetic organisms is the pentose
phosphate pathway, by glucose-6-phosphate dehydrogenase (G6PDH)
in the first step. The pentose phosphate pathway also produces pentose,
another important part of NAD(P)H, from glucose. Some bacteria also
use G6PDH for the Entner–Doudoroff pathway, but NADPH production
remains the same.
20. RoleofPrecursormetabolites
• Precursor metabolites are intermediate molecules in catabolic and
anabolic pathways that can be either oxidized to generate ATP or can be
used to synthesize macromolecular subunits such as amino acids,
lipids, and nucleotides as shown in Figure
23. RoleofEnergyrichcompounds
• Energy can be stored in the chemical bonds within molecules in the cell,
but not all chemical bonds are equally energetic. When broken, some
bonds will release more energy than others. A phosphate is a
phosphorus atom bonded to three oxygen atoms (PO3). When it’s
bonded to another molecule, the bond between them is called a
phosphate bond. Breaking the phosphate bond releases a lot of energy.
24. RoleofEnergyrichcompounds
• There are mainly two classes of energy rich compounds formed in the
cell which fulfill the energy requirements;
Compounds having high energy anhydrous phosphoester bond.
- ATP, GTP, CTP, TTP, UTP
Compounds having high energy thioester bond.
-In chemistry thioesters are compounds with the functional group
R–S–CO–R'.
-In biochemistry, the best-known thioesters are derivatives of
coenzyme A, e.g., acetyl-CoA.
25. Role of ATP
• Adenosine triphosphate (ATP) is an organic compound and hydrotrope
that provides energy to drive many processes in living cells.
• Found in all known forms of life, ATP is often referred to as the
"molecular unit of currency" of intracellular energy transfer.
•When consumed in metabolic
processes, it converts either to
adenosine diphosphate (ADP) or to
adenosine monophosphate (AMP).
26. Role of ATP
• The hydrolysis of ATP into ADP and inorganic phosphate releases 30.5
kJ/mol of enthalpy, with a change in free energy of 3.4 kJ/mol. The
energy released by cleaving either a phosphate (Pi) or pyrophosphate
(PPi) unit from ATP at standard state of 1 M are:
• ATP + H2O → ADP + Pi
• ATP + H2O → AMP + PPi
ΔG° = −30.5 kJ/mol (−7.3 kcal/mol)
ΔG° = −45.6 kJ/mol (−10.9 kcal/mol)
27. Role of ATP
• Biochemical functions includes:
• Uptake of nutrients
• Activation of most substrate molecules so that they are able to enter
the cell metabolism
• Biosynthesis of most cellular molecules, nucleic acids, chromosome
replication (DNA replication), and cell division and cell growth.
• Amino acid activation in protein synthesis
• ATP binding cassette transporter
• Extracellular signalling
28. Role of other energy rich compounds
High Energy
compounds
Structure Role in metabolism
GTP Guanosine-P-P-P Energy transfer, Genetic Translation,
CTP Cytidine-P-P-P Phospolipid biosynthesis, substrate in
the synthesis of RNA, coenzyme in
metabolic reactions
UTP Uridine-P-P-P Polysaccharide, peptidoglycan
biosynthesis
TTP Thymidine-P-P-P one of the four nucleoside
triphosphates that make up DNA,
synthesis of lipopolysaccharides
Acetyl CoA CH3CO-S CoA Fatty acid biosynthesis
