6 Using microorganisms Flashcards
What are microorganisms?
Microorganisms are living things that you can only see with the help of a
microscope.
What are the bodies of most microorganisms made of?
The ‘bodies’ of most microorganisms are made of a single cell, although sometimes millions of cells are gathered together to form a colony.
What is a characteristic of the colony of cells in relation to their visibility?
They may then be visible to the human eye.
What are the critical roles of microorganisms?
Microorganisms have critical roles to play in recycling the waste products
of organisms, as well as recycling the organisms themselves when they die.
Why are many types of microorganisms studied?
Many types of microorganisms are studied because they cause disease in
animals and plants.
Apart from disease, what do microorganisms do?
On the other hand, humans have made use of the great reproductive capacity of microorganisms to make useful products, such as food, drink and medicines.
What is a picture showing the few examples of many types of microorganisms?
What is fermentation?
Using the respiration of microorganisms to produce useful products.
What are fermenters?
A vessel used to grow microorganisms.
How do microorganisms respire?
Many microorganisms respire anaerobically.
What is fermentation normally used for?
Fermentation is normally used to make a useful product.
What is biotechnology?
It is the use of microorganisms to make useful products.
How is bread produced?
Fermentation by yeast.
How is yoghurt made?
By the action of bacteria on milk.
How is cheese made?
Other bacteria and moulds are used in cheese manufacture.
What can we do now that we understand what is happening when fermentation takes place?
Nowadays we understand what is happening when fermentation takes place, and can use biotechnology to produce not just foods but also a huge range of products, from medicines like penicillin to chemicals such as enzymes and fuels.
What has modern biotechnology allowed us to do?
Modern biotechnology also allows us to alter the genes of microorganisms so
that they code for new products.
What is this process called?
Genetic engineering.
What is genetic engineering?
Techniques used to transfer genes from the cells of a donor organism to those of a recipient.
What do we use traditional biotechnology for?
- Making drinks.
- Making bread.
- Making yoghurt.
What happens when yeast cells are deprived of oxygen?
They respire anaerobically.
What happens during this anaerobic respiration?
They break sugar down into ethanol and carbon dioxide.
what is the equation for anaerobic respiration?
Glucose → Ethanol + Carbon dioxide
What is this process used for?
To make bread.
How is wine made?
Wine is made by using yeast to ferment sugars in grape juice.
Where does commercial wine production take place?
Commercial wine production takes place in large containers called vats.
What do these vats do?
They prevent air from reaching the wine and ensure conditions remain anaerobic.
How is homemade wine made?
Homemade wine is produced in small-scale fermenters fitted with an ‘airlock’,
What does this airlock do?
It allows carbon dioxide to escape but prevents the entry of oxygen.
When does fermentation stop?
The alcohol increases in concentration until it kills the yeast cells, at which point fermentation stops.
What is beer made from?
Beer is made from barley.
What does barley contain?
Barley contains starch rather than sugars so the starch needs to be broken down first.
How is the starch broken down first?
This happens by allowing the barley
seeds to germinate.
How does germination break down the starch?
When they start to germinate they produce the enzyme amylase, which breaks down starch into the sugar maltose.
What does amylase do?
It breaks down starch into the sugar maltose.
What happens to the maltose from the seeds?
It is fermented by yeast in a large open vat.
What is yeast also used for?
It is also used to make bread.
What forms the bread dough?
Wheat flour and water are mixed together and yeast added, forming the bread dough.
What do enzymes from the original cereal grains do?
Enzymes from the original cereal
grains break down starch to sugars, which are respired by the yeast.
What is done during this stage?
Extra sugar may be added at this stage.
What happens during bread making in terms of yeast?
In bread-making, the yeast begins by
respiring aerobically, producing water and carbon dioxide.
What does the carbon dioxide do?
The carbon dioxide makes the dough rise.
What happens when the air runs out?
When the air runs out, conditions become anaerobic.
What happens to the yeast when the conditions become anaerobic?
The yeast begins to respire anaerobically making ethanol and more carbon dioxide.
What happens when the dough is baked in the oven?
The gas bubbles expand.
What do these expanding gas bubbles do?
This gives the bread a light, cellular texture.
What does baking also do?
It kills the yeast cells and evaporates any ethanol from the fermentation.
What is a practical that we can do in terms of anaerobic respiration?
We can investigate the rate of anaerobic respiration in yeast.
What is an apparatus that is used in the practical to investigate the rate of anaerobic respiration in yeast?
What is step 1 in this practical to investigate the rate of anaerobic respiration in yeast?
A small amount of water is gently boiled in a boiling tube to remove any
air that is dissolved in the water.
What is step 2 in this practical to investigate the rate of anaerobic respiration in yeast?
The water is allowed to cool, and a small amount of sugar (glucose or sucrose) is dissolved in the water. Finally, a little yeast is added and the mixture is stirred.
What is step 3 in this practical to investigate the rate of anaerobic respiration in yeast?
A thin layer of liquid paraffin is added to the surface of the mixture,
How is this liquid paraffin added to the surface of the mixture?
Using a pippette.
How do we make sure that oxygen is kept out?
The boiled water ensures that there is no oxygen in the mixture, and the layer of paraffin stops any oxygen diffusing in from the air.
What is step 4 in this practical to investigate the rate of anaerobic respiration in yeast?
A control apparatus is set up.
What is different about this control apparatus?
This is exactly the same as before, except that boiled (killed) yeast is used instead of living yeast.
What is step 5 in this practical to investigate the rate of anaerobic respiration in yeast?
Both sets of apparatus are left in a warm place for an hour or two.
What will be seen in the mixture with the living yeast?
The mixture with living yeast will be seen to produce gas bubbles.
where does this gas go?
The gas passes through the delivery tube and into the indicator in the second boiling tube.
What happens if this tube contains limewater?
It will turn cloudy (milky).
What happens if this tube contains hydrogen carbonate indicator?
The indicator will change from orange to yellow.
What do these changes in the indicators show?
This shows that the gas is carbon dioxide.
What do we record?
The time taken for the indicator to change colour is recorded and compared with the control (which will not change)
What happens if the bung is taken out of the first boiling tube and the liquid paraffin is removed using a pipette?
The tube will smell of alcohol.
What predictions can be tested using this method?
- The type of sugar (glucose, sucrose, maltose etc.) affects the rate of
respiration of the yeast. - The concentration of sugar affects the rate of respiration of the yeast.
- How temperature affects the rate of respiration of the yeast.
How can the rate be found?
The rate can be found by timing how quickly the indicator changes colour,
or from the rate of production of bubbles of carbon dioxide.
What is yoghurt?
Yoghurt is milk that has been fermented by certain species of bacteria, called lactic acid bacteria.
What is lactic acid bacteria?
It is a type of bacteria that produces lactic acid. Used in fermenting milk to make yoghurt and cheese.
What is the effect of fermentation on this milk?
It is to turn the liquid milk into a semi-solid food with a sour taste.
How is yoghurt made?
To make yoghurt, milk is first pasteurised at 85–95 °C for 15–30 minutes.
Why is the milk pasteurised?
To kill any natural bacteria that it contains.
What follows pasteurisation?
It is the homogenised.
Why is it homogenised?
To disperse the fat globules.
What then happens to the milk?
The milk is then cooled to 40–45 °C and inoculated with a starter culture of two species of bacteria, called Lactobacillus and Streptococcus.
What do these bacteria do?
These bacteria produce lactic acid, as well as starting to digest the milk
proteins
What temperature is the bacteria kept at?
The culture is kept at this temperature for several hours while the pH falls to about 4.4.
Why do we wait for the pH to fall to about 4.4?
As these are the optimum conditions for the bacteria.
What happens as the pH has dropped?
The mixture coagulates (thickens) as the drop in pH causes the milk proteins to denature and turn into semi-solids.
Why are two reasons for why the pH drop is necessary?
- Reduces the reproduction of
the lactic acid bacteria (although it doesn’t kill them). - It also helps to prevent
the growth of other microorganism.
Why do we want to prevent the growth of other microorganisms?
To preserve the nutrients in the
milk.
What happens when fermentation is finished?
The yoghurt is stirred and cooled to 5 °C.
What is added following the cooling?
Flavourings, colourants and fruit may then be added before it is packaged for
sale.
What is a flow chart showing the stages in yoghurt production?
What is a fermenter?
It is a vessel used to grow microorganisms.
What are two examples of a simple sorts of fermenters?
- A glass jar used to make homemade wine is a simple sort of fermenter.
- Even a baking tray containing a ball of dough could be defined as one.
What can industrial fermenters contain?
Industrial fermenters are large tanks that can hold up to 200 000 dm3 of a
liquid culture.
Why are industrial fermenters used?
They enable the environmental conditions such as temperature, oxygen and carbon dioxide concentrations, pH and nutrient
supply to be carefully controlled so that the microorganisms will yield their
product most efficiently.
What happens to these factors?
They are carefully controlled.
Why are these factors carefully controlled?
So that the microorganisms will yield their product most efficiently.
What is a diagram that shows a simplified industrial fermenter?
What is the inlet?
At the start of the process,
nutrients are fed in through
pipes which can be opened
and closed using valves.
What is the air inlet?
If the organisms respire
aerobically, filtered air is
supplied through this inlet.
The air is filtered to
prevent contamination.
What is the cold water outlet?
Fermentation produces heat, so
to prevent the contents from
overheating, the fermenter is
surrounded by a water jacket
through which cold water
circulates, keeping the
temperature at the best level
for growth.
Why are the stirring paddles used?
Stirring paddles mix up the contents.
This keeps the microorganisms in
suspension in the liquid, so that they
get more exposure to the nutrients,
and helps to keep the temperature
even throughout the vessel. Some
fermenters use jets of air to mix the
contents instead of paddles.
What do fermenters have to be made of?
Many microorganisms produce
acidic waste products, so fermenters
have to be made of materials which
will not corrode, such as stainless
steel or special alloys.
What happens when fermentation is completed?
When fermentation is completed, the products are collected through an outlet pipe.
What must be done before the fermenter is filled with new nutrients and culture?
The inside of the tank and all the pipes must be cleaned and sterilised.
How is this sterilisation done?
This is usually done with very hot steam under high pressure.
What are two factors that are likely to develop if the fermenter is not sterile?
- Any bacteria or fungi that manage to
get in would compete with the organism in the culture, reducing the yield of product. - The product would become contaminated with waste products or cells of the ‘foreign’ organism.
What is the name given to the methods used to prevent contamination by unwanted microorganisms?
Aseptic precautions.
