3 marksTable 1 lists a number of chemical substances.
Table 1
hydrogen |
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water |
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sulfur |
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silicon |
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titanium |
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nitrogen |
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carbon |
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Place a tick (✓) in the boxes next to the chemical elements that are found naturally in living organisms.
1 markName a group of biological molecules that contain carbon, hydrogen and oxygen only.
1 markName the molecule that, in certain fats, binds to three fatty acid molecules.
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5 marksFig. 1 shows five food tests and the food groups that those tests are designed to be used for.
Fig. 1
Using five straight lines, link each food test to the food group that the test is used for.
2 marksDescribe the colour change that is observed when a sample of food has tested positive in the Benedict's test.
3 marks(i) Describe two safety precautions that need to be taken when performing the Benedict's test on a sample of food.
[2]
(ii) Describe one additional safety precaution when performing the ethanol emulsion test on a sample of food.
[1]
2 marksA student tested a sample of three different foods for starch.
The student's partial results are shown in Table 1.
Table 1
food sample | colour of test sample after testing |
lasagne | blue/black |
fish |
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bread |
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Complete Table 1 to predict the results that would be obtained.
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1 markA student processed a sample of food into an aqueous solution and tested it with a test solution. The test solution changed from blue to violet.
Name the solution used in this test.
1 markState the food group that the experiment in part (a) showed a positive result for.
1 markA sample of butter was shaken with ethanol, followed by an equal volume of cold water.
Predict the appearance of the mixture after the addition of water.
2 marksA sample of freshly-squeezed orange juice was mixed with DCPIP solution.
Predict the result of this food test, and explain your prediction.
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7 marksThis question is about biological molecules.
Choose words or phrases from the list to complete the sentences.
Each word or phrase may be used once, more than once, or not at all.
calcium | carbon | carbon dioxide | carbohydrate |
cellulose | chloroplasts | fat | glycerol |
glycogen | iron | methane | nitrogen |
oxygen | protein | starch |
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Fats are composed of the elements .............................................. , hydrogen and .............................................. only. All proteins contain these three elements and the element .............................................. .
Glucose is a type of ............................................... . Animals store excess glucose as .............................................. in the liver.
Plants store excess glucose as .............................................. . Plants also convert glucose to .............................................. which is used to make cell walls.
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2 marksTable 1 contains some statements about biological molecules.
Table 1
| Correct? (✓) |
They contain carbon, hydrogen and oxygen only |
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All are sugars |
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They are all formed from long chains of glucose molecules |
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They are the principal energy source in the animal diet |
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They include starch, cellulose and triglycerides |
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They form solids at room temperature but melt into liquids when warmer |
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The sequence of the building blocks determines their function |
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Place ticks (✓) in Table 1 to indicate statements that apply to carbohydrates.
3 marksCompare the chemical elements found in carbohydrates and proteins.
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2 marksFig. 1 shows the components of fats and oils as shapes.
Using these shapes, sketch the appearance of a triglyceride molecule that would be found in fats and oils.
Fig. 1
3 marksTable 1 contains some statements about the fate of proteins in an animal's body.
Table 1
A. | Protein undergoes chemical digestion |
B. | Amino acids circulate in the blood |
C. | Food is ingested |
D. | Peptides are put together in protein synthesis |
E. | Peptides are synthesised |
Place these events into a logical chronological order.
1st | ➙ | 2nd | ➙ | 3rd | ➙ | 4th | ➙ | 5th |
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2 marksDescribe the test that would be used to show a positive result for the presence of protein in a sample of food.
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2 marksTable 1 shows four samples of food that were tested for glucose (reducing sugar) using the Benedict's test.
Table 1
test number | contents |
1 | Water |
2 | Potato juice |
3 | Dilute orange juice |
4 | Glucose sports drink e.g. Lucozade™ |
The results are shown in Fig.1
Fig. 1
The Benedict's test is referred to as being semi-quantitative.
Use the information provided in Table 1 and Fig. 1 to suggest what the term 'semi-quantitative' means.
2 marksExplain the purpose of the test tube containing just water in the experiment shown in Fig. 1.
2 marksExplain why the test for lipids is known as an emulsion test.
3 marksPredict the colour changes (if any) of the iodine test on the food samples shown in Table 2.
Table 2
food sample | iodine test result |
Bagel |
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Eggs |
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Fish |
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Rice |
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Grapefruit |
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