3 marks
Table 1
| hydrogen | |
| water | |
| sulfur | |
| silicon | |
| titanium | |
| nitrogen | |
| carbon |
Place a tick (✓) in the boxes next to the chemical elements that are found naturally in living organisms.
1 mark1 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
.
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 | |
| bread |
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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2 marksTable 1 contains some statements about biological molecules.
Table 1
| Correct? (✓) | |
| They contain carbon, hydrogen and oxygen only | |
| All are sugars | |
| They are all formed from long chains of glucose molecules | |
| They are the principal energy source in the animal diet | |
| They include starch, cellulose and triglycerides | |
| They form solids at room temperature but melt into liquids when warmer | |
| The sequence of the building blocks determines their function |
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 |
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 marks
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 marks
Table 2
| food sample | iodine test result |
| Bagel | |
| Eggs | |
| Fish | |
| Rice | |
| Grapefruit |
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