Food tests

The passage describes carbohydrates used in different organisms. Complete the passage by writing a suitable word in each blank space.

Carbohydrates contain the elements carbon, hydrogen and_........ .

Plant cell walls are made of the carbohydrate,_........ . Plants store carbohydrate as starch. The starch in plant cells is_........ so it has no osmotic effect on the cell. The simple test for starch is to add a few drops of_........ solution to a sample. If the test is positive, the solution changes colour from_........ to_........ .

The storage carbohydrate in animals is_........ , which is found mainly in the muscles and in the_........ . If the blood glucose concentration increases then the hormone,_........ , is released by the_........ . This causes the conversion of blood glucose into the storage carbohydrate.

The diagram shows the alimentary canal of a rabbit with some parts labelled.

The table lists descriptions of some parts of the alimentary canal. Complete the table by giving the correct part from the diagram to match each description. One has been done for you.

Explain how the liver helps digestion in the alimentary canal.

Rabbits eat grass. The diagram shows the cell wall of a leaf cell from a grass plant. Complete the diagram by drawing and labelling other structures in this leaf cell.

Grass cell walls are made of cellulose. Rabbits cannot digest cellulose. Bacteria living in the large intestine of rabbits can digest cellulose into glucose. Rabbits eat their own faeces to obtain this glucose.

Give two differences between the structure of bacterial cells and the structure of plant cells.

Describe a test to show that rabbit faeces contain glucose.

A student investigates the movement of substances from the gut into the blood using a model. The Visking tubing bag represents the gut and water represents the blood. Visking tubing is permeable to small molecules.

The student puts different solutions of various substances into the bag. After 20 minutes he carries out food tests on the water.

Complete the table to show the results obtained by the student. One has been done for you.

Explain how the volume of the bag would change when it only contains starch solution.

Describe the test the student should use to find out if glucose is present in the water.

Explain how you could use this apparatus to investigate the effect of bile on the digestion of lipid.

Students carried out an experiment about kidney function. Their teacher provided them with three samples of artificial urine.

• one sample contained the same composition as urine from a person with normal kidneys

• one sample contained the same composition as urine from a person with diabetes, who is unable to produce insulin

• one sample contained the same composition as urine from a person with high blood pressure

The students tested the samples for glucose and for protein. The table shows their results.

High blood pressure occurs when the heart has to pump very hard to force blood through narrow arteries.

Use information from the table and your own knowledge to explain which sample could be from a person with high blood pressure.

Use information from the table and your own knowledge to explain which sample could be from a person with diabetes.

Describe the test for glucose.

Suggest why the teacher uses artificial urine rather than real urine in this experiment.

A student is given two samples of carbohydrates. He tests to see if one is glucose and the other one is starch. Describe the two chemical tests he should use to identify each carbohydrate.

Different groups of organism store carbohydrate as different molecules. Complete the table to show an example from each group of organisms and the molecule they use to store carbohydrate.