2005
DRAW AND LABEL A DIAGRAM TO SHOW THE BASIC STRUCTURE OF A BACTERIAL CELL
STATE TWO WAYS IN WHICH A BACTERIUM DIFFERS FROM A HUMAN CELL
Bacteria contain a plasmid which is a circular piece of dna containing genes, which allow bacteria to resist antibiotics
DESCRIBE HOW BACTERIA RESPOND IN ORDER TO SURVIVE WHEN ENVIRONMENTAL CONDITIONS BECOME UNFAVOURABLE
By producing endospores
- These are formed when dna replicates
- The new strand becomes enclosed in a tough walled capsule called an endospore
- Parent cell breaks down and endospore remains
- When conditions are favourable the spores absorb the water, break walls and reproduce by binary fission.
WHAT IS MEANT BY PATHOGENIC
The cell has membrane-bound nucleus and membrane-bound organelles
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2006
DISTINGUISH BETWEEN PHOTOSYNTHETIC AND CHEMOSYNTHETIC BACTERIA
Photosynthetic bacteria use light to make their food. Eg purple sulfur bacteria
Chemosynthetic bacteria use chemical reactions to make food (energy). Eg Nitrifying bacteria in soil.
2 FORMS OF HETEROTROPHIC NUTRITION FOUND IN BACTERIA
Saprophytic - feed off of dead organic matter. Eg bacteria of decay
Parasitic - feed of a living host. Eg disease causing bacteria. E Coli
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2008
LOG
Settling in phase.
Bacteria are producing the enzymes necessary to digest the nutrients.
Rate of growth begins to increase towards the end of this phase.
LAG
Rapid period of growth during phase due to the fact that:
Bacteria have developed the necessary enzymes and there is plenty of nutrients.
Few waste products being produced.
Rate of division is currently at its maximum doubling every 20 times
STATIONARY
Rate of growth levels off because
- Nutrients are being used
- Build up toxins produced by bacteria themselves
- Rate at which new cells are produced is = to the rate at which other cells are dying.
DEATH
More bacteria are dying than being produced because
- Very few nutrients left
- Many bacteria are poisoned by the toxins
- Thus rate of growth falls
- Endospores may form to survive harsh conditions
DISTINGUISH BETWEEN BATCH AND CONTINUOUS FLOW
Batch processing is when a fixed sterile nutrient is added to the bioreactor. Batch processing undergoes the stages of the bacteria growth curve.The product is then separated in the end. The equipment is cleaned and sterilised.
In Continuous Flow the factors are carefully monitored to ensure that it is always in the log phase. The nutrients are continuously being added while the products are simultaneously being removed.
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2010
DESCRIBE HOW OXYGEN DEMAND CHANGES AS BACTERIA IN THE WATER CHANGES.
Oxygen demand increases,as bacteria increases
The relationship is directly proportional
This is because more bacteria need more oxygen
ASEPSIS means that measures have been taken to exculde unwanted organisms
STERILE means that all micro organisms are destroyed.
INOCULATION is the addition of cells to the nutrient medium
INCUBATION is the growing of the micro organism in a warm environment
BIOREACTOR a vessel which biological reactions occur.
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2017
GIVE A BENEFIT AND DISADVANTAGE OF BACTERIA
Benefit
Antibiotics can be made
Lactobacillus converts milk to cheese and yogurt
Disadvantage
Food spoilage
Pathogenic bacteria can cause disease in humans and animals
HOW DOES BACTERIA REPRODUCE
By binary fission
- Dna is replicated
- Cell elongates and the 2 chromosomes separate and move to either side
- Cell wall pinches into to divide the cell into 2
- Two identical daughter cells are formed
- There little mixing of genes and variation