Download B6 Understanding microbes

Understanding Microbes – Revision Pack (B6)
Bacteria:
Bacterial cells have many features that
allow them to survive:
-
They have a flagellum (tail) for
movement
They have a cell wall to maintain its
shape and stop it bursting
They have DNA (nucleoid) which
controls the cells activities and
replication of the cell
NOTE – bacteria cells come in many
different shapes and sizes; they can be
spherical, rod-shaped, spiral or curved rods.
Bacteria reproduce by splitting into two – this is a type of asexual reproduction which
is known as binary fission.
You can get bacteria to reproduce an agar plate but you MUST sterilise all the
equipment beforehand to prevent contamination – this is called an aseptic
technique.
In terms of numbers, bacteria are very successful; this is because:
-
They can survive off of a lot of different energy sources
They can survive in a great number of habitats
Some survive by taking in organic nutrients BUT some can make their own
food
Bacteria reproduce at a very fast rate; this means they can very quickly spoil food or
cause disease. This means that they must be handled carefully as to avoid
contaminating food, people or animals.
Yeast:
Yeast is a single-celled fungus that is grown for
many functions. You can alter the growth rate
of yeast by:
-
Changing food availability
Changing Temperature
Changing pH
Removing waste products
The growth rate of yeast doubles for every
10oC rise until its optimum is reached; so if at
200C, it was growing at a rate of 40, at 30oC it
would be growing at a rate of 80.
Understanding Microbes – Revision Pack (B6)
Viruses:
Viruses are NOT living cells but very
small structures made up of a
protein coat surrounding a strand
of genetic material.
Viruses can only reproduce under
certain conditions:
-
They only reproduce inside
other living cells
They only attack specific
cells (e.g. plant, animal etc)
A virus reproduces in a few simple steps:
STEP 1 – it attaches itself to the host cell
STEP 2 – it injects its genetic material into the cell
STEP 3 – it uses the cell to make components of new viruses
STEP 4 – it will then cause the host cell to die to release the new viruses
Understanding Microbes – Revision Pack (B6)
Past Papers:
PPQ(1):
PPQ(2):
Understanding Microbes – Revision Pack (B6)
PPQ(3):
PPQ(4):
Understanding Microbes – Revision Pack (B6)
Mark Schemes:
PPQ(1):
PPQ(2):
PPQ(3):
PPQ(4):