October 06 [Mon], 2014, 16:53
This week we looked more into Fungi, mainly looking at the works of yeast.

When the word Fungi is mentioned, I have always thought this only meant about the different mushrooms however through this weeks lesson I found that the term points to three main types of organisms. These are: single celled organisms (yeast) and multi-cellular organisms (moulds and mushrooms). The organisms 'respire' to gain energy, the term is often confused with breathing however it referes to the process of gaining energy from food with carbon dioxide as their waste product.
food equation:
Glucose (Sugar/food) + Oxygen --Respiration--> Carbon Dioxide + Energy (Heat)

Experiement 1) Dough Racers - to investigate how the products of respiration by micro-organisms are needed to make the dough rise. Additionally the effects of temprature on the process.
Variables: temprature

-2 Beakers
-some ice
-hot water
-3 plastic/paper cups
in each cup:
-6tsp flour
-1tsp sugar
-10ml water
-1tsp Yeast suspention
-cling film

1) put the ingredients in the cup and knead thoroghly so that the dough and make sure all three doughs are about the same softness and thickness then cling film each.
2) fill in 1 beaker with ice and some water, the other with how water.
3) then place 1 cup of dough into the beaker so it the dough sits in the cold water.
4) similarly place another cup of dough into the hot water
5) observe for 15 minutes and record the data.

becareful with the amount of water you add as it may cause the dough to become too watery or too dry like these..


The dough in the hot beaker seemed to have rise quite well compared to the cold dough. however the results could be replicated for further reliability. As all of our dough did not rise to what we had expected.

Expeiment 2) Balloon bottles - to investigate the effect of the mass of sugar on respiration by yeast.
Variable: Amount of sugar (none, 2.5tsp, 5tsp)

-3 bottles
-3 balloons
-dry yeast

1) place each amount of sugar into each bottle (none, 2.5tsp, 5tsp), 1tsp of dry yeast and 10ml of water.
2) shake well and place the ballon of the mouth of the bottle
3) observe and record the results

our experiment did not succeed. we suspect that there was not enough water in the solution for the yeast to react and as a result osmosis occured and killed off the reaction. *osmosis- too high sugar concentration and the water inside the yeast being replaced and become unable to function.

this is another groups results:

best : medium amount of sugar
worst: too much sugar
Therefore we found out that yeast needs sugar for it to respire. however like humans yeasts have a storage of sugar (glucose) in their bodies thus they are able to repire and we are able to see the reactions in the bottle with no sugar content. On the other hand when there is too much sugar in the solution this slows down or even kills off the yeast cells and prevent them from respiring.

Follow up experiment.. as we found out how yeast works.
expeiment 3) Juice Fermenters - investigating the sugar content in fruit juices
varable: different juices

-3 differnt type of juices (Grape, Strawberry and rhubarb, cranberry and raspberry)
-dry yeast
-3 bottles

1) pour in 100ml of each juice into separate bottles, 1tsp of yeast and close the lid.
2) shake well
3) observe and record the findings


Strawberry and rhubarb had the most sugar content in the 3 juices.
we had a discussion of which one had the most as we also found out in the previous experiment that too much sugar would cause osmosis, however because it is juice which would be less likely to have over dose of sugar we concluded that the one with the most froth (most production of CO2) would be the one with the most sugar content. We could do this experiment with the children and work on healthy eating.

yeast is also used for brewing
when they do not have enough oxygen they would respire anaerobically as a result produces alcohol
Glucose --anaerobic respiration--> ethanol + carbon dioxide (+ energy released)
animals also have similar reactions: glucose → lactic acid (+ energy released) eg) an animal being chased by a preditor. lactic acid is the reason you get muscle pains the day after a extensive work out!

other uses of Fungi is decomposition;
both bacteria and fungi cause decay by relasing enzymes to break down dead matter. this is extensively used in making compost and fertilizers.

there are also Harmful fungis that we need to watch out for..
some fungis live on living organisms and infects the organisms.
eg) athlete's foot, oral thrush in babies
most cases anti-fungal medication works to get rid of these harful fungis.

we also prepared another experiement to show the effect of these medications
experiment 4) yeast - investigating the effects of anti-fungal creams

- agar
- yeast
- anti-fungal cream

1) make a yeast agar
2) divide it into three sections with a pen on the case of agar.
3) place two filtered paper with different anti-fungal cream on
4) observe and record the findings

we have control, athlete's foot cream and thrush

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