what is the size of a typical bacterial cell?
just a few microns (thousandths of a mm
how can bacteria be classified?
by their shape
how do bacteria reproduce?
by splitting in two
when can bacteria produce rapidly?
in suitable conditions
how can bacteria be grown?
in large fermenters
properties of a flagellate bacillus
- flagellum
- cell wall
- bacterial DNA
what is yeast?
a fungus
properties of a yeast cell?
- nucleus
- cytoplasm
- cell wall
- bud.
what are viruses?
- not living cells
* much smaller than bacteria and fungi
Describe how yeast reproduces asexually by
budding
the chromosomes are copied and a new nucleus is made. The new cell ‘buds’ off the parent.
Describe how the parts of bacterial cells relate to their function
• flagellum for movement
• cell wall to maintain shape, and to stop it from
bursting
• DNA to control the cell’s activities and replication
of the cell.
Describe the main shapes of bacteria
- spherical
- rod
- spiral
- curved rods
how do bacteria reproduce?
by a type of asexual reproduction called binary fission
Describe aseptic techniques for culturing bacteria on
an agar plate
- clean the work surface with bleach before and after using bacteria
- wash your hands before and after handling bacteria and wear gloves
- sterilise all equipment before and after use with disinfectant or in an autoclave
- keep lids on culture dishes where bacteria are growing, and destroy all bacteria at end of experiment
Describe the structure of viruses
- a protein coat
* surrounding a strand of genetic materia
what can viruses do?
- can only reproduce in other living cells
- only attack specific cells
- may attack plant, bacterial or animal cells
Explain how a virus reproduces
• attaching itself to a specific host cell
• injecting its genetic material into the cell
• using the cell to make the components of new
viruses
• causing the host cell to split open to release the
viruses.
Describe how yeast growth rate can be increased, its
optimum growth rate being controlled by:
- food availability
- temperature
- pH
- removal of waste products
Explain how bacteria:
• can survive on an enormous range of energy
sources
• can exploit a very wide range of habitats
because bacteria can use so many different sources of nutrients and energy, they are able to survive in a very wide variety of habitats.
Explain the consequences of very rapid bacterial
reproduction in terms of food spoilage and disease
- diseases spread fast as conditions inside the human body are ideal for bacterial growth
- food can become contaminated by the toxic waste produced by bacteria as they feed, making it very dangerous to eat
Describe how yeast growth rate doubles for every 10°C rise in temperature until the optimum isreached
yeast growth doubles for every 10°C rise in temperature. So, increasing the temperature increases the rate of fermentation. But, over 40 degrees C, yeast enzymes are denatured, which causes the rate of fermentation to slow down.
