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Fungi and Yeast
Yeast is a single celled fungus. Other examples of organisms include: mushrooms and mould.
Yeast cells are bigger than a bacterial cell and can be clearly seen under a microscope. They
are useful in food production in bread making and alcohol.
The Features of a Fungal Cell:
The yeast cell is very similar to a
plant cell. The cell wall is different
though because it is made of chitin
instead that makes it tougher.
These cells usually are budding
together in a clump and are rarely on
Reproduction in Yeast:
Yeast cells reproduce asexually in a process known as budding. The original cell divides and
creates a new cell, which often stay together. The process is very fast and the population
can increase rapidly. Optimum growth is controlled by: availability of food, temperature, pH
and the amount of waste products.
For every 10 °C rise in temperature, the growth rate of yeast doubles until it gets to the
optimum temperature which then the enzymes become denatured.
Yeast can respire anaerobically or aerobically. When yeast respires anaerobically, it produces
ethanol, carbon dioxide and energy. It is known as fermentation and is used to make beer
and wine. When yeast respires aerobically, it does not produce the ethanol and is used for
the carbon dioxide release to make cakes rise when being cooked. Yeast reproduces more
quickly through aerobic respiration as more energy is available from the oxygen. The faster
the yeast reproduces the more glucose it will have broken down. This is the only way to
measure how fast yeast is reproducing.