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Micro-Organisms
Micro-OrganismsMicro-organisms are tiny living
organisms.All living organisms feed, grow
and reproduce.
All living organisms have a life cycle to ensure survival.
Some micro-organisms can be useful whereas others can be
harmful.
Different micro-organisms are found in different places/habitats.
Key VocabularyBacteriaBacteriumBugGermMicrobe
Mould PasteurizeSteriliseVirusYeast
Micro-organisms are too small to be seen with
the naked eye!500 bacteria would only cover a full stop!You would need 160 000 000
000 bacteria to fill a teaspoon!!
A colony of micro-organisms
Some micro-organisms can be harmful!
Certain bacteria can make stone decay…as well as
teeth!!!
Clean Those Teeth!Design a dental
hygiene poster which gives advice about how to
keep your teeth and
gums healthy (4-6 bits of advice!!).
Preventing Micro-organisms Spreading
Micro-organisms can spread illnesses and diseases in a variety of ways including:
Coughs and sneezesTouching infected people or objectsInsect bitesInfected food
Stop Them Spreading!!
List as many ways as you can of preventing the spread of micro-
organisms.
Kitchen HygieneIt is very important to
prevent microbes spreading in the kitchen because this
could lead to food poisoning!
Food/Personal Hygiene
Task 1: Complete information text
about the spread of microorganisms
Task 2: Design a Personal Hygiene poster (A4 paper).
Making Food Using Micro-organisms
Some foods are made using micro-organisms.These include…..
YeastYeast is a micro-
organism which is used in the making of
bread!
Technical VocabularyTechnical Vocabulary
Kneading – pressing and folding the dough with your hands until it is smooth and stretchy. This spreads the yeast evenly around the dough and helps it to rise.
Knocking back – deflating the dough with a GENTLE punch. This evens out the texture of the bread.
Proving – this is the correct name for the process of rising in bread making.
Rising – the time it takes for the dough to increase in size.
Yeast If you’ve ever taken a bite of bread you’ve
made, you may wonder how simple ingredients like flour, salt and yeast can produce raised, sometimes wonderfully bubbly bread.
It makes people a little squeamish to know it that yeast makes bread dough rise because it is a live single-celled organism.
Specifically it is a variety of fungi called Saccharomyces cerivisiae, which is harnessed to eat, drink and be merry, before dying a quick death when exposed to oven heat.
Yeast You can buy several different types
of yeasts on the market. The first of these is called live or
fresh yeast. This is relatively unstable, requiring refrigeration, and it has a very short shelf life.
Dried versions, sold in packages or cubes is essentially cells of Saccharomyces cerivisiae, which are waiting to be activated.
Yeast Like many fungi types, yeasts for bread dough
responds to warm water, which begins to bring the little cells to life.
Then when exposed to sugars in bread and in flour, it begins to eat, digesting portions of these sugars. This eating process goes on for a short period of time only.
Eventually the yeast will die within a few hours, especially if the dough is allowed to grow cold or exposed to too much air.
Don’t feel too sorry for it when you have a slice of bread, as its life would be short under any circumstances. At least by using it for bread or wine, you get to give this fungus a happy and full life.
Yeast It might be embarrassing to the yeast to
have to admit that this rapid eating/digestion cycle makes it just a trifle gassy.
As Saccharomyces cerivisiae is feasting, it begins to release gas bubbles of carbon dioxide, and small amounts of ethanol alcohol. These bubbles, trapped in the bread dough, cause the rising action with which we’re familiar.
This is why bread making can be time consuming; you’ve got to let this fungus work for a couple of hours in order to sufficiently rise dough.
Yeast Once dough has been acted upon by fungi,
not all of the cells are quite dead. Putting the bread in the oven is relatively macabre, from the standpoint of the yeast (if it had a point of view).
The heat from the oven makes remaining cells go into overdrive, madly munching away at the sugars and expelling carbon dioxide prior to expiring from the oven heat.
This is why bread continues to rise during its early cooking stages, and then may deflate slightly as cooking continues.
Bread Rising
Yeast There are a few things that inhibit these
microbes from their natural function. Too much salt can halt its rising action.
Therefore bread dough recipes usually contain a little salt and a little sugar for balance.
Fats can also inhibit the fungi, and you’ll note that breads that have butter in them, especially salted butter may not have the same rise due to the butter’s presence.
If we add more sugar I think that….
If we add more yeast I think that…
When the yeast is mixed with sugar and water, dough is created and
when it is left to ‘prove’ the yeast reproduces and makes CO2 which makes
the dough ‘rise’.
Preserving FoodIn order to prevent food
‘going off’, it can be preserved/stored in the
following ways.Freezing
DehydratingCanningPickling
Freezing Dehydrating
Canning Pickling
We cannot survive without some micro-
organisms!Microbes are essential to
life on earth.
Without any microbes, we would be left with
mountains of waste material that wouldn’t
decay.
Helpful Micro-organisms
What A Lotta Rot!
Average rotting times for some household waste products are:Orange peel and banana skin:
2 years!!
Crisp Packet:
20 years!!Aluminium Drinks Can:
100 years!!
Glass bottle:1000 000
years!!!Plastic Bottle:
Possibly never if not
biodegradable!!!
Will it Rot or Not?!
Draw a dustbin and inside it draw those items that are not easily biodegradable. Outside the bin, draw those items that are biodegradable.
Another word for a material that will rot is…..BIODEGRADABLE
MouldWhen you
see mouldy food, you are seeing colonies
(groups) of microbes.
Investigating Micro-OrganismsOur Challenge:
Discover the conditions microbes require to grow well.Explain whether the evidence shows that microbes are living things.
Mould Investigation PlannerQuestion
Equipment
We Will Keep Constant We Will Change
Method
Mould Investigation FindingsDescribe what the
results of the investigation show.
What conditions do micro-organisms
prefer? How do you know?
Are micro-organisms living things?
How do you know?
Research TasksCompile a factfile on
either:1. Louis Pasteur 2. Anton Van Leewenhoek
3. Alexander FlemingWrite an information text on:
4. Preserving Food5. Good Microbes!
We cannot survive without some micro-
organisms!Microbes are essential to
life on earth.
Without any microbes, we would be left with
mountains of waste material that wouldn’t
decay.
Helpful Micro-organisms
Food/Personal Hygiene
Task 1: Complete a powerpoint
explaining all about helpful micro –
organisms!
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