8C Physiology - Digestive System
The digestive system is composed of organs which have the ability to break food down into
small molecules. These molecules are then absorbed into the bloodstream. Enzymes are
involved in digestion as it aids the breakdown of food molecules by catalysing the substrate.
All enzymes are biological catalysts.
Practicals of Food Tests:
(starch, proteins, lipids, reducing and non-reducing sugars, vitamin C content)
Test for Lipids (Emulsion Test):
The aim of this experiment is to test the presence of lipids in a biscuit, crisps and a kiwi.
(In a molecular structure, Lipids consist of a chain of hydrocarbons and oxygen. Lipids are
foods containing fats and oils.)
Apparatus:
Biscuit
Crisps
Kiwi
Filter paper
Ethanol
Pestle & Mortar
6 x test tubes
Test tube rack
Pipette
Spatula
Method:
1. Using a pestle and mortar, I crushed up the biscuit and crisps, into a fine powder. As
the kiwi was liquid, I left this step out.
2. Next, I transferred the biscuits, crisps and kiwi samples into individual test tubes.
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3. Next, into each test tube, I added 2 of ethanol, and shook the test tube thoroughly,
to evenly spread the ethanol through the food samples.
4. Next, I allowed the solid to settle for three minutes, to allow the liquid to be extracted.
5. Then I decanted the liquid from the three test tubes into separate test tubes.
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6. Then, I added 2 of deionized water to the second test tube, and made
observations.
Results of the experiment:
, Food sample: Observation Conclusion
Biscuit After observing the liquid from the biscuit, I The cloudy ethanol
determined that the ethanol had turned indicated that there are
cloudy. lipids present in the biscuit
Crisps After observing the liquid from the biscuit, I The cloudy ethanol
determined that the ethanol had turned indicated to me that there
cloudy. are lipids present in the
crisps.
Kiwi After observing the liquid from the kiwi, I The clear ethanol indicated
determined that the ethanol had remained to me that there were no
clear lipids present in the kiwi.
This image shows the
ethanol colour of the biscuit,
crips and kiwi.
Test for Vitamin C (DCPIP Test):
The aim of this experiment is to test if an orange, bell pepper and a kiwi contain Vitamin C.
Apparatus:
Slice of Orange
Slice of bell pepper
Slice of kiwi
Cotton ball
Watercolour paper
Beaker
DCPIP
Method:
, 1. To begin, I obtained a slice of the orange, bell pepper and kiwi
2. Then, I used a cotton ball to add some DCPIP to the water colour paper.
3. Then I arranged the food samples on the paper, ensuring they were spread across
the paper, facing the freshly cut side on the paper
4. I left the food samples for 15 minutes and observed the bright blue colour of the
DCPIP disappear on the paper.
Results of this experiment:
Food Sample: Observation: Conclusion:
Orange After observing the orange, I The disappeared DCPIP indicated to
determined that the colour of me that there is Vitamin C present in
the DCPIP had disappeared the orange.
surrounding the orange and
underneath it.
Bell pepper After observing the bell pepper, The disappeared DCPIP indicated to
I determined that the colour of me that there is Vitamin C present in
the DCPIP had disappeared the bell pepper.
surrounding the bell pepper
and underneath it.
Kiwi After observing the kiwi, I The disappeared DCPIP indicated to
determined that the colour of me that there is Vitamin C present in
the DCPIP had disappeared the kiwi.
surrounding the kiwi and
underneath it.
This image shows the DCPIP had
disappeared underneath and around
the orange, bell pepper and kiwi.
Protein Test (Biuret Test):
The aim of this experiment is to test if egg, orange and banana smoothie and spinach
contain proteins.
