1. Fungi have no chlorophyll
so cannot make their own food by
How do fungi
1. As parasites
2. As saprophytes
(feed on a living
host, causing it
(feed on dead and
Parasitic fungi on (i)
nails and (ii) trees.
2. Fungi do not produce
flowers. Reproduce by
3. Fungi are mainly found in
damp and shady places.
Question: SEP, 2011
Give a biological explanation for each of
the following statements.
Fungi are rarely found in brightly lit
Do not photosynthesise.
Lack a waxy cuticle – avoid drying up by
avoiding such environments.
4. The basic unit of a fungus is a hypha
and not a cell.
B. cell wall
A hypha (plural = hyphae) is a thread-like
structure having a cell wall made of chitin.
Part of a hypha
Fungi store food as:
glycogen or oil, but not starch
A network of hyphae: a
hyphae are either white or grey
A hypha grows out of
a germinating spore
Two types of hyphae:
hyphae: are erect
belongs to the group of fungi called moulds –
it is a pin mould
lives on damp, organic (has carbon) matter
Structure of Mucor
by producing spores
i) small & light:
to be carried easily by
the wind or insects
to increase chances
Nutrition in Mucor
3. Nutrients are
absorbed from all
over the hyphae.
2. Digestion takes place
outside the body.
Fungi are useful:
1. Decay dead material and are important to
recycle nutrients in the soil
2. Decompose sewage
3. Are used to make the antibiotic penicillin
4. Are eaten e.g. mushrooms
5. Yeast is useful to make bread, wine and beer
Fungi are harmful:
1. Parasitic fungi causes diseases
in animals and plants
2. Spoil food, clothes, leather and walls
Athlete’s foot in
Rusts in wheat
Let us study YEAST:
2. Economic importance
A single yeast cell
Yeast is a unicellular fungus
1. Dough making
flour, yeast, sugar &
water are mixed to
make a dough
Water must be warm and
NOT boiling. WHY?
The living yeast cells
ferment the sugar to
give off carbon
After 1 hour in a warm
place the dough has
risen.A close-up of the dough.
What happens to the
alcohol during baking?
It evaporates on baking.
Explain why it is important to
produce a very sticky dough after
mixing the ingredients together. (2)
Carbon dioxide remains inside the
dough. The gas makes the dough
The ‘holes’ in the
bread are made by
the carbon dioxide
This gives the bread a
What happens to the
yeast when the dough
is baked in the oven?
Dies. The heat kills it.
Question: SEP, 2007
Give biological reasons for the following
Yeast is added to flour for the pizza dough to rise.
Yeast releases carbon dioxide by fermentation. As
carbon dioxide escapes, it makes the dough rise.
Barley seeds are
soaked in water so that
enzymes are made
Enzymes convert the
stored starch into
the seeds are crushed with water
the resulting liquid is boiled with hops to
give it a flavour
The main stages in the brewing of beer are
given in the diagram below.
Barley or other cereal grains germinatedStage A
Germinated grains crushed in water
Yeast added to solution (from Stage B) and
mixture placed in closed vats fitted with
one-way exit valve
Yeast dies and falls to bottom
a) Name the
b) What conditions are needed for the
barley to germinate?
Water, a correct temperature, oxygen
c) Describe the action of the yeast on the
solution in Stage C. (3)
Yeast ferments the sugar into carbon
dioxide, ethanol and energy. The
process is anaerobic.
d) Why were the vats closed and fitted with
one-way exit valves in Stage C? (3)
To prevent microbes & oxygen from
entering. To allow carbon dioxide to
escape or else the fermenter bursts.
e) What was the most likely cause of death
of the yeast in Stage D? (Assume that the
supply of food was adequate.) (1)
abundant on sugary
surfaces of ripe fruit
but can also be added
Grapes are crushed:
the sugar they contain is
fermented by yeasts to
produce alcohol & CO2.
What is the use of an ‘airlock?
allows CO2 to escape
prevents microbes from entering
Why does the balloon inflate?
sugar, CO2 is
Question: MAY, 2004
The apparatus used to make wine was
sterilised before being used. Why is
sterilisation of the apparatus important?
To kill bacteria as they can convert
ethanol into ethanoic acid. Vinegar
would be produced instead of wine.
Different varieties of grapes produce
different types of wine
Question: MAY, 2012
Some winemakers add sucrose to
unfermented grapes. What is the effect of
this sucrose addition on the alcohol
content of the wine produced? (1)
Increase in alcohol content.
Question: SEP, 2007
1) Humans have used yeast to produce
pizza dough. Describe briefly TWO
other beneficial ways in which yeast
has been utilised by human beings for
economic benefits. (4)
2) Suggest TWO advantages and ONE
disadvantage for yeast cells when
included in these processes. (3)
Other uses of yeast:
As SCP (single cell protein)
In genetic engineering experiments
Question: SEP, 2012
Yeast is a fungus.
a) Give ONE characteristic of fungi. (2)
b) Name the type of asexual reproduction
performed by yeast cells. (1)
c) Give ONE disadvantage of asexual