1. PRIMARY METABOLISM

3. FUNCTIONS OF METABOLISM
ANABOLIC
• Change nutrients into structural and
functional components of the organism
CATABOLIC
 • Extract chemical energy or nutrient element
such as N and S from complex nutrients to
provide E and materials for anabolic reactions

4.  Anabolism depends on catabolism for E in the
form of NADH,ATP and NADPH.
 Also for the production of key intermediates
for functional macromolecules synthesis

5. Primary Metabolism
 The metabolic events that are important to
functions of fungus in pure culture

6.  Secondary metabolism coextensive with
primary metabolism
 The division into primary and secondary
depends on the distribution of the
metabolites among the organisms.
 Eg of metabolites?
 Organic acid, vitamin, antibiotics etc.

7. Carbon and Energy Metabolism
 Glucose metabolism
 Non-carbohydrates function as sole sources
of C, must be convertable to glucose by a
process called gluconeogenesis
 Provide precursors for cell wall , glycoproteins
and other materials derived directly from
hexoses.

8. Glycolysis
 Glycolysis:
 the breakdown of glucose by enzymes, releasing
energy and pyruvic acid
 3 pathways for hexoses:
1. EM (Embden-Meyerhof-Parnas)
2. HM (Hexose monophosphate )
3. ED (Entner-Doudoroff)

9. Glycolysis of Pentoses
 2 pathways:
1. XP (xylitol pathway)
2. PK (phosphoketolase pathway)
 EM, HM and XP pathways are universal in
fungi
 PK widespread among yeasts
 ED – only for Tilletia caries and Caldariomyces
fumago

11.  Although EM and HM pathways lead through
G3P to pyruvate but different metabolic
functions.
 EM uses NAD as electron acceptor.
 HM leads to the reduction of NADP to
NADPH.
 There are other sources of reduced NADP for
biosynthetic purposes besides HM pathway.

12. Fermentation
 Regeneration of NAD by the transfer of
electrons from NADH to an organic electron
acceptor generated by the metabolism of the
foodstuff.
 In fungi this electron acceptor is pyruvate

13. Types of Fermentation
 1. Alcoholic
 2. Lactic acid
 3. Mixed acid fermentation
Pyruvic acid as electron acceptor

14. ALCOHOLIC FERMENTATION
 Pyruvate to ethanol and CO2
 Saccharomyces
 Aspergillus, Fusarium and Mucor are well
known for this ability but obligate aerobes.

15. LACTIC ACID FERMENTATION
 Found primarily in Chytridomycetes,
Oomycetes and Zygomycetes
 Rhizopus, a member of Zygomycete, carry
out lactic acid fermentation together with
alcoholic fermentation.

16. Mixed Acid Fermentation
 Found in a small group of Chytridiomycetes
 Similar to mixed acid fermentation of
Enterobacteriaceae with acetate, lactate,
formate, ethanol, methane, CO2 and H2 as
end products.

17. RESPIRATION
 In fungi is similar to that in other organisms.
 3 interdependent processes
1. Citric acid cycle
2. Electron transport
3. Oxidative phosphorylation
 Mitochondrion: center of respiration

18.  TCA is a central hub of both catabolic and
anabolic metabolism.
 • ETC – 2nd critical process in respiration

19. ALTERNATIVE RESPIRATION
 2 alternate pathways of electron transport
that are distinct from the cytochrome path.
 Differ from the cytochrome path in being
insensitive to cyanide and sensitive to either
salycil hydroxamate (SHAM) or azide.

20.  • SHAM-sensitive pathway accepts electrons as the
level of ubiquinol and transports them to O2 without
proton transport
 Without phosphorylation of ADP.
 Azide-sensitive pathway also lack proton transport
capability.
 The alternative pathways are readily demonstrable
when the normal pathway is blocked or limited.

21. ENERGY METABOLISM OF FUNGI
Group
Name
Respiration Fermentatio
n
Anaerobic
growth
Fungi
Obligate
respirers
Yes No No Many yeasts and
most
filamentous fungi
Aerobic
respirers
Yes Anaerobic in
pregrown
cells
No A few yeasts and
filamentous fungi
Aerobic
fermentors
Limited Aerobic and
Anaerobic
No Schizosaccharomyces
pombe and other
yeasts
Facultative
aerobic
fermentors
Limited Aerobic and
Anaerobic
Facultative Saccharomyces
cerevisiae
Obligate
anaerobes
Absent Anaerobic Obligate Rumen
Chytridiomycetes

22. OTHER DEGRADATIVE PATHWAYS
 Serve several functions:
1. Release of NH4 for reutilization
2. Provision of carbon metabolites utilizable as
C and E sources
3. Detoxification of inhibitory compounds
 Example: degradation of amino acids, purines
and pyrimidines.

23. GLUCONEOGENESIS
 Required f o r growth on noncarbohydrate
carbon sources
 Involves substrates closely related to the EM
pathway and requires the reversal of this
process.
 general property of fungi.