The document provides instructions for a final exam in mycology. It states that the exam has two sections, Section A which is compulsory and Section B which requires answering three of five questions. Section A includes six short answer questions covering topics like distinguishing fungi from plants, industrial uses of fungi, differences between molds and yeasts, and terms like biotrophs, necrotrophs, parasexuality, and mycotoxins. Section B includes longer answer questions requiring descriptions of fungal reproduction, advantages of incomplete septa, heterokaryosis, growth conditions for fungi, glycolysis and energy production in fungi, and differences between batch and continuous culture techniques.

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MULUNGUSHI UNIVERSITY
SCHOOL OF SCIENCE, ENGINEERING AND TECHNOLOGY (SSET)
DEPARTMENT OF SCIENCE, MATHEMATICS AND STATISTICS
2019/2020 ACADEMIC YEAR SEMESTER I
BIO 361: MYCOLOGY
FINAL EXAMINATION
DATE: 16th DECEMBER, 2019
DURATION: THREE (3) HOURS TOTAL MARKS: 100
INSTRUCTIONS:
1. There are two sections in this paper; SECTION A and SECTION B
2. There are FIVE (5) questions in this paper.
3. Answer only four (4) questions.
4. SECTION A is COMPULSORY, and attempt any other THREE (3) questions from
SECTION B.
5. All questions carry equal marks (25 Marks)
This paper consists of 3 printed pages

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DO NOT TURN THE PAGE UNTIL YOU ARE TOLD TO DO SO.
SECTION A: COMPULSORY QUESTION
Question 1
a) You are shown an object that looks superficially like a mushroom. Describe at least three
criteria (including anatomical and chemical traits) that would enable you to tell whether
the object is a piece of a plant or a piece of a fungus. [4 Marks]
ANS:
I. Presence of chrolophyll in plants
II. Chitin in the cell wall of the fungus
b) How is fungi utilized in some industries? [4 Marks]
ANS: Fungi are used in the production of chemicals and also in the drug manufacturing
industries.
c) Fungi can be differentiated into two basic types based on the macroscopic appearance of
their colonies. Describe the difference between molds and yeasts. [4 Marks]
ANS: Mold is a type of fungus that grows in multicellular filaments called hyphae.
These tubular branches have multiple, genetically identical nuclei, yet form a single
organism, known as a colony. In contrast, yeast is a type of fungus that grows as a single
cell.
d) Explain the difference between biotroph and necrotroph. [4 Marks]
ANS: biotrophs derive energy from living cells, they are found on or in living plants,
can have very complex nutrient requirements and do not kill host plants rapidly;
necrotrophs derive energy from killed cells; they invade and kill plant tissue rapidly and
then live saprotrophically on the dead remains;
e) Write short note on:
i. Parasexuality [2 Marks]
ANS: A phenomenon, involving a complex form of mitosis, whereby two cell
nuclei merge without any sexual process and the chromosome count is doubled.
ii. Mycotoxin [2 Marks]
ANS: Mycotoxins are secondary metabolites produced by fungi that are capable
of causing disease and death in humans and other animals.
f) Differentiate among the members of the following pairs of related terms:
i. hypha/mycelium [2.5 Marks]
ANS: Hyphae are the masses of branched, tubular, thread-like filaments about 4-
6 micrometers in diameter that penetrate into substrates and absorb nutrients.

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Hyphae branch into a complicated and expanding patchwork called a mycelium
which forms the thallus, or vegetative part of the fungus.
ii. ectomycorrhiza/endomycorrhiza [2.5 Marks]
ANS: Ectomycorrhizae (ECM) • “Ecto-” means outside and in the case of ECM
it means the fungal hyphae do not normally penetrate into healthy cortical cells of
the plant. Endomycorrhizae, also called arbuscular mycorrhizae, do not form a
dense sheath over the root. Instead, the fungal mycelium is embedded within the
root tissue.
[25 Marks]
SECTION B: ANSWER ANY OTHER THREE (3) QUESTIONS
Question 2
a) Describe in details the main types of reproduction that occur in fungi? [10 Marks]
ANS: Fungi can reproduce asexually by fragmentation, budding, or producing spores, or
sexually with homothallic or heterothallic mycelia.
Asexual Reproduction
Fungi reproduce asexually by fragmentation, budding, or producing spores. Fragments of
hyphae can grow new colonies. Mycelial fragmentation occurs when a fungal mycelium
separates into pieces with each component growing into a separate mycelium. Somatic
cells in yeast form buds. During budding (a type of cytokinesis), a bulge forms on the
side of the cell, the nucleus divides mitotically, and the bud ultimately detaches itself
from the mother cell.
The most common mode of asexual reproduction is through the formation of asexual
spores, which are produced by one parent only (through mitosis) and are genetically
identical to that parent. Spores allow fungi to expand their distribution and colonize new
environments. They may be released from the parent thallus, either outside or within a
special reproductive sac called a sporangium.
Sexual Reproduction
Sexual reproduction introduces genetic variation into a population of fungi. In fungi,
sexual reproduction often occurs in response to adverse environmental conditions. Two
mating types are produced. When both mating types are present in the same mycelium, it
is called homothallic, or self-fertile. Heterothallic mycelia require two different, but
compatible, mycelia to reproduce sexually.
Although there are many variations in fungal sexual reproduction, all include the
following three stages. First, during plasmogamy (literally, “marriage or union of
cytoplasm”), two haploid cells fuse, leading to a dikaryotic stage where two haploid
nuclei coexist in a single cell. During karyogamy (“nuclear marriage”), the haploid nuclei

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fuse to form a diploid zygote nucleus. Finally, meiosis takes place in the gametangia
(singular, gametangium) organs, in which gametes of different mating types are
generated. At this stage, spores are disseminated into the environment.
b) What is the advantage to having incomplete septa? [3 Marks]
ANS: These types of hyphae are also called aseptate or coenocytic. They represent a
more primitive form of fungi and are the ancient ancestors of septate hyphae.
Non-septate hyphae are the result of the nucleus repeatedly dividing but not the
cytoplasm. This can result in many nuclei in the cytoplasm along with other organelles
such as ribosomes, endoplasmic reticulum, and Golgi apparatus.
c) What is heterokaryosis? [3 Marks]
ANS: Heterokaryosis is the association of genetically distinct nuclei in a common hyphal
cytoplasm, and is a process involved in the generation of fungal variation. The fusion of
the distinct nuclei within a heterokaryotic hypha produces a heterozygous diploid nucleus
and is one of the stages of the parasexual cycle.
d) Which fungal nuclei are diploid? Which are haploid? To what do the following terms
refer: heterokaryotic, homokaryotic, dikaryotic, and monokaryotic? [4 Marks]
e) Describe the growth conditions required by fungi. [5 Marks]
ANS: Conditions for best fungal growth:-
1. Temperature: 25- 30 degree celcious.
2. Humidity: high moist humid environment.
3. pH: Moulds differ in their pH requirements. Most will grow well over the pH
range 3-7. Some such as Aspergillus niger and Penicillium funiculosum can
grow at pH 2 and below.
4. Nutrients: Nutrient requirements for moulds may vary from mould to mould.
Some moulds may thrive well on substrates with high sugar or salt content.
Some may prefer simple sugars while others have the ability to utilize complex
sugars.
5. Light: Many moulds species grow well in the dark, but some prefer daylight or
alternate light and darkness for them to produce spores.
6. Aeration: Nearly all moulds require air to grow.
[25 Marks]
Question 3
a) Describe how energy is produced from glucose in a fungal cell. [10 Marks]
ANS: Glycolysis
For bacteria, eukaryotes, and most archaea, glycolysis is the most common pathway for
the catabolism of glucose; it produces energy, reduced electron carriers, and precursor
molecules for cellular metabolism. Every living organism carries out some form of
glycolysis, suggesting this mechanism is an ancient universal metabolic process. The

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process itself does not use oxygen; however, glycolysis can be coupled with additional
metabolic processes that are either aerobic or anaerobic. Glycolysis takes place in the
cytoplasm of prokaryotic and eukaryotic cells. It begins with a single six-carbon glucose
molecule and ends with two molecules of a three-carbon sugar called pyruvate. Pyruvate
may be broken down further after glycolysis to harness more energy through aerobic or
anaerobic respiration, but many organisms, including many microbes, may be unable to
respire; for these organisms, glycolysis may be their only source of generating ATP.
The type of glycolysis found in animals and that is most common in microbes is the
Embden-Meyerhof-Parnas (EMP) pathway, named after Gustav Embden (1874–1933),
Otto Meyerhof (1884–1951), and Jakub Parnas (1884–1949). Glycolysis using the EMP
pathway consists of two distinct phases (Figure 8.10). The first part of the pathway,
called the energy investment phase, uses energy from two ATP molecules to modify a
glucose molecule so that the six-carbon sugar molecule can be split evenly into two
phosphorylated three-carbon molecules called glyceraldehyde 3-phosphate (G3P).
Glycolysis produces pyruvate, which can be further oxidized to capture more energy. For
pyruvate to enter the next oxidative pathway, it must first be decarboxylated by the
enzyme complex pyruvate dehydrogenase to a two-carbon acetyl group in the transition
reaction, also called the bridge reaction (see Appendix C and Figure 8.12). In the
transition reaction, electrons are also transferred to NAD+ to form NADH. To proceed to
the next phase of this metabolic process, the comparatively tiny two-carbon acetyl must
be attached to a very large carrier compound called coenzyme A (CoA). The transition
reaction occurs in the mitochondrial matrix of eukaryotes; in prokaryotes, it occurs in the
cytoplasm because prokaryotes lack membrane-enclosed organelles.
The Krebs cycle transfers remaining electrons from the acetyl group produced during the
transition reaction to electron carrier molecules, thus reducing them. The Krebs cycle
also occurs in the cytoplasm of prokaryotes along with glycolysis and the transition
reaction, but it takes place in the mitochondrial matrix of eukaryotic cells where the
transition reaction also occurs. The Krebs cycle is named after its discoverer, British
scientist Hans Adolf Krebs (1900–1981) and is also called the citric acid cycle, or the
tricarboxylic acid cycle (TCA) because citric acid has three carboxyl groups in its
structure. Unlike glycolysis, the Krebs cycle is a closed loop: The last part of the
pathway regenerates the compound used in the first step (Figure 8.13). The eight steps of
the cycle are a series of chemical reactions that capture the two-carbon acetyl group (the
CoA carrier does not enter the Krebs cycle) from the transition reaction, which is added
to a four-carbon intermediate in the Krebs cycle, producing the six-carbon intermediate
citric acid (giving the alternate name for this cycle). As one turn of the cycle returns to
the starting point of the four-carbon intermediate, the cycle produces two CO2
molecules, one ATP molecule (or an equivalent, such as guanosine triphosphate [GTP])
produced by substrate-level phosphorylation, and three molecules of NADH and one of

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FADH2. (A discussion and detailed illustration of the full Krebs cycle appear in
Appendix C.)
Although many organisms use the Krebs cycle as described as part of glucose
metabolism, several of the intermediate compounds in the Krebs cycle can be used in
synthesizing a wide variety of important cellular molecules, including amino acids,
chlorophylls, fatty acids, and nucleotides; therefore, the cycle is both anabolic and
catabolic (Figure 8.14).
b) Differentiate between liquid Batch culture and liquid Continuous culture. [5 Marks]
ANS: Batch culture technique is also called as closed system of cultivation. In this
technique at first nutrient solution is prepared and it is inoculated with inoculum (culture
organism) and then nothing is added in the fermentation tank except aeration. In batch
culture, neither fresh medium is added nor used up media is removed from the
cultivation vessel. Therefore volume of culture remains same.
Continuous culture technique is also called as open system of cultivation. In this
technique fresh sterile medium is added continuously in the vessel and used up media
with bacterial culture is removed continuously at the same rate. So the volume and
bacterial density remain same in the cultivation vessel. In this technique, bacteria grow
continuously in their log phase. This type of growth is known as steady state growth.
The cell density in continuous culture remains constant and it is achieved by maintaining
constant dilution and flow rate.
c) Define gametangium. [2 Marks]
ANS: A cell or organ (as of an alga, fern, or fungus) in which gametes are developed.
d) What is the ecological importance of fungi? [3 Marks]
ANS: Fungi & Their Roles as Decomposers and Recyclers
Fungi play a crucial role in the balance of ecosystems. In these environments, fungi play
a major role as decomposers and recyclers, making it possible for members of the other
kingdoms to be supplied with nutrients and to live.
The food web would be incomplete without organisms that decompose organic matter.
Some elements, such as nitrogen and phosphorus, are required in large quantities by
biological systems; yet, they are not abundant in the environment. The action of fungi
releases these elements from decaying matter, making them available to other living
organisms. Trace elements present in low amounts in many habitats are essential for
growth, but would remain tied up in rotting organic matter if fungi and bacteria did not
return them to the environment via their metabolic activity.

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e) If all the fungi on Earth were suddenly to die, how would the surviving organisms is
affected? [4 Marks]
ANS:
f) What are mycorrhizas? Describe the ecological importance of mycorrhizas? [3 Marks]
ANS: A mycorrhiza is a symbiotic association between a fungus and a plant. Arbuscular
mycorrhizal fungi (AMF) are elements which are key to improving crop productivity and
soil quality.
[25 Marks]
Question 4
a) Describe the degradation of cellulose by cellulase complex.[8 Marks]
ANS: Cellulases are mainly produced by microorganism like fungi and bacteria
that catalyze the breakdown of cellulose materials into simpler monosaccharides.
These enzymes are glycosyl hydrolases which are categorized into some families.
Cellulases are generally subdivided into four major classes with regard to the
mode of action and substrate specificity. These are exoglucanases,
endoglucanases, β-glucosidases, and cellobiohydrolases.
These enzymes are specifically important in hydrolyzing crystalline cellulose.
In nature, complete cellulose hydrolysis is mediated by a combination of three
main types of cellulases:
1. Endoglucanase (1,4-β-d-glucanohydrolase, EC 3.2.1.4), randomly attacks the
internal O-glycosidic bonds, resulting in glucan chains of different lengths;
2. Exoglucanase (1,4-β-d-glucan cellobiohydrolase, EC 3.2.1.91), acts on the ends of
the cellulose chain and releases β-cellobiose as the end product;
3. β-Glucosidase (β-d-glucoside glucohydrolase, EC 3.2.1.21), an enzyme that
hydrolyzes terminal, nonreducing β-d-glucosyl residues with release of β-d-
glucose
b) Define the following terms
i. Primary metabolite [2 Marks]
ANS: A primary metabolite is a kind of metabolite that is directly involved in
normal growth, development, and reproduction.
ii. Secondary metabolite [2 Marks]
ANS: Secondary metabolites (SMs) are defined as heterogeneous low-molecular-
weight compounds that are not required for the organism growth. Fungi use

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secondary metabolites for different purposes, e.g., protection from predation, from
environments stress, for communication, competition and toxicity against other
microbes, and pathogenicity.
c) Describe how the haustorium develops from the spore. [4 Marks]
ANS: A haustorium (plural haustoria) is a rootlike structure or a structure that
grows into or around another structure to absorb water or nutrients. Spore
germinate with a germ tube which differentiates into a well defined appressorium.
A penetration hypha is formed, which enters the leaf through the stomatal
opening. A vesicle is formed within the stomatal cavity from which an infection
hypha emerges. Upon contact with a mesophyll cell a haustorial mother cell is
differentiated from which a haustorium is formed.
d) Does passive dispersal or forcible discharge of spores generally result in further dispersal
of fungal spores? Explain. [4 Marks]
ANS: Passive spore release
A mature puffball is typically a flexibly-walled, apically open sack of spores. A
raindrop or foot hitting the sack momentarily compresses the air inside thereby
forcing a puff of spores through the apical hole and several centimetres into the
air. You can see this for yourself if you flick a puffball with your finger. While
some sort of impact triggers the initial release of the spores from the fruiting
body, wind takes over as the agent of longer distance dispersal.
Active spore release
Once again, we'll start with a common mushroom growing in the middle of a
field. As explained in the TWO MAJOR GROUPS SECTION the gills of a
mushroom are lined with spore-bearing basidia. When a spore is mature it is
forcibly shot from the basidium, into the air space between the gills. This is
explained in more detail in the MUSHROOM SPORE DISCHARGE SECTION.
While the spore is ejected horizontally with considerable force (up to 25,000
times the force of gravity), air resistance stops the spore in a fraction of a
millimetre. The air in the space between two gills is still, so after coming to a stop
the only influence on the spore is gravity and the spore falls downward.
e) Explain the roles of vesicles and microtubules in fungal apical growth. [5 Marks]
ANS: Filamentous fungi are extremely polarized organisms, exhibiting
continuous growth at their hyphal tips. The hyphal form is related to their
pathogenicity in animals and plants, and their high secretion ability for
biotechnology. Polarized growth requires a sequential supply of proteins and
lipids to the hyphal tip. This transport is managed by vesicle trafficking via the
actin and microtubule cytoskeleton.

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[25 Marks]
Question 5
a) What is the composition of the fungal cell wall? Why is this composition an advantage
to the fungi? [7 Marks]
ANS: Like plant cells, fungal cells have a thick cell wall. The rigid layers of
fungal cell walls contain complex polysaccharides called chitin and glucans.
Chitin (N-acetyl-D-glucosamine), also found in the exoskeleton of arthropods
such as insects, gives structural strength to the cell walls of fungi. The wall
protects the cell from desiccation and some predators. Fungi have plasma
membranes similar to those of other eukaryotes, except that the structure is
stabilized by ergosterol: a steroid molecule that replaces the cholesterol found in
animal cell membranes. Most members of the kingdom Fungi are nonmotile.
However, flagella are produced by the spores and gametes in the primitive
Phylum Chytridiomycota.
The cell wall is vital to the growth, survival, and morphogenesis of fungi.
Mutational analysis has proved that it provides a protective barrier against a wide
range of environmental conditions such as heat, cold, desiccation, and osmotic
stress. It also provides protection against other microbes.
Cell wall sensor proteins allow the fungus to assess and respond to changes in the
environment. Cell wall adhesion and mucins mediate the adhesive properties of
the fungal cell and play critical roles in allowing fungi to colonize new
environments. The cell wall is also critical for participation in biofilm formation,
a process that many fungi engage in, and is an important ecological niche for
many fungi. For pathogenic fungi, the cell wall is critical for virulence and
pathogenicity. The wall provides both adhesive properties critical for invasion of
host tissue and protection against the host defense mechanisms.
b) Fungi are non-motile. How are they dispersed to new areas? [5 Marks]
ANS: Fungi and plants are sessile (immobile). Unlike animals, they cannot walk
or fly to new habitats. Their immobility generally leaves only two ways for fungi
and plants to extend their range: they can grow into an adjoining area, or disperse
spores or seeds. Spore dispersal is a two-step process. The first step is spore
discharge or release. The second step is dispersal away from the parent. Fungi
have evolved a number of different mechanisms for spore discharge and dispersal.
i. Wind and Water Dispersal
ii. Animal Dispersal
iii. Catapulting Spores

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c) What are lichens? Explain how the partners benefit. [4 Marks]
ANS: Lichens have been described as "dual organisms" because they are
symbiotic associations between two (or sometimes more) entirely different
types of microorganism
- a fungus (termed the mycobiont)
-a green alga or a cyanobacterium (termed the photobiont).
The mycobiont has two principal roles in the lichen symbiosis:
 to protect the photobiont from exposure to intense sunlight and
desiccation to absorb mineral nutrients from the underlying surface
or from minute traces of atmospheric contaminants.
The photobiont also has two roles:
 to synthesise organic nutrients from carbon dioxide in the case of
cyanobacteria, to produce ammonium (and then organic nitrogen
compounds) from N2 gas, by nitrogen fixation. In some
ecosystems such as desert soils, tundra heaths, and Douglas-fir
forests of the Pacific Northwest of the USA, lichens can provide
the major input of nitrogen which supports other forms of life
d) Write short note on:
i. Mycelial strands [2 Marks]
ANS: Mycelial cords are linear aggregations of parallel-oriented hyphae. The
mature cords are composed of wide, empty vessel hyphae surrounded by
narrower sheathing hyphae. Mycelial cords are capable of conducting nutrients
over long distances. For instance, they can transfer nutrients to a developing
fruiting body, or enable wood-rotting fungi to grow through soil from an
established food base in search of new food sources.
ii. Appresorium [2 Marks]
ANS: An appressorium is a terminal simple or lobed swollen structure of
germtubes or infection hyphae. It adheres to the surface of the host and helps in
the penetration of hyphae of the pathogen.
e) Describe how fungi acquire nutrients. [5 Marks]

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ANS: Fungi get their nutrition by absorbing organic compounds from the environment.
Fungi are heterotrophic: they rely solely on carbon obtained from other organisms for
their metabolism and nutrition. Fungi have evolved in a way that allows many of them
to use a large variety of organic substrates for growth, including simple compounds such
as nitrate, ammonia, acetate, or ethanol. Their mode of nutrition defines the role of fungi
in their environment.
Fungi obtain nutrients in three different ways:
They decompose dead organic matter. A saprotroph is an organism that obtains its
nutrients from non-living organic matter, usually dead and decaying plant or animal
matter, by absorbing soluble organic compounds. Saprotrophic fungi play very
important roles as recyclers in ecosystem energy flow and biogeochemical cycles.
Saprophytic fungi, such as shiitake (Lentinula edodes) and oyster mushrooms (Pleurotus
ostreatus), decompose dead plant and animal tissue by releasing enzymes from hyphal
tips. In this way they recycle organic materials back into the surrounding environment.
Because of these abilities, fungi are the primary decomposers in forests (see Figure
below).
They feed on living hosts. As parasites, fungi live in or on other organisms and get
their nutrients from their host. Parasitic fungi use enzymes to break down living tissue,
which may causes illness in the host. Disease-causing fungi are parasitic. Recall that
parasitism is a type of symbiotic relationship between organisms of different species in
which one, the parasite, benefits from a close association with the other, the host, which
is harmed.
They live mutualistically with other organisms. Mutualistic fungi live harmlessly
with other living organisms. Recall that mutualism is an interaction between individuals
of two different species, in which both individuals benefit.
Fungal hyphae are adapted to efficient absorption of nutrients from their environments,
because hyphae have high surface area-to-volume ratios. These adaptations are also
complemented by the release of hydrolytic enzymes that break down large organic
molecules such as polysaccharides, proteins, and lipids into smaller molecules. These
molecules are then absorbed as nutrients into the fungal cells. One enzyme that is
secreted by fungi is cellulase, which breaks down the polysaccharide cellulose.
Cellulose is a major component of plant cell walls. In some cases, fungi have developed
specialized structures for nutrient uptake from living hosts, which penetrate into the host
cells for nutrient uptake by the fungus.
[25 Marks]
END OF EXAMINATION