Biological Molecules

9.What type of bond holds the two strands of DNA together?

10.A student adds Benedict's solution to a food sample and heats it. The colour remains blue. What does this indicate?

11.If one strand of DNA has the base sequence A C G T, what is the sequence on the complementary strand?

12.In the emulsion test for lipids, what is added to the food sample before adding cold water?

13.A student tests four food samples with iodine solution and Biuret solution: | Sample | Iodine test | Biuret test | |---|---|---| | A | Blue-black | Blue | | B | Orange-brown | Violet | | C | Blue-black | Violet | | D | Orange-brown | Blue | Which sample contains both protein and starch?

14.A student adds Benedict's solution to a food sample and heats it. The colour changes from blue to brick red. Which conclusion is correct?

15.A food sample is tested with DCPIP solution. The blue colour disappears. Which nutrient is present?

16.A triglyceride molecule is composed of one glycerol molecule and three fatty acid chains. What is the ratio of glycerol to fatty acid molecules in a triglyceride?

17.Which of the following is a disaccharide?

18.Which elements are found in all proteins?

19.In the general structure of an amino acid, which part is described as the R group?

20.In a triglyceride molecule, one glycerol molecule is bonded to three fatty acid chains by ester bonds. Which part forms the central backbone of the molecule?

21.A sample of DNA contains 30% adenine. What percentage of guanine is present?

22.A student tests a food sample with iodine solution and observes a blue-black colour. She then tests the same sample with Benedict's solution and heats it, but the colour remains blue. What does this indicate?

23.In the ethanol emulsion test for lipids, what is the positive result?

24.Which row correctly matches the food test with its positive result?

25.A student adds DCPIP to a sample of orange juice. The blue colour disappears. What does this indicate?

26.A food sample is tested with Biuret solution and turns violet. Which nutrient is present?

27.A student tested a food sample and obtained the following results: iodine test – blue-black; Benedict's test (after heating) – brick-red; Biuret test – blue; emulsion test – cloudy white. Which nutrients are present?

28.A student performed the ethanol emulsion test on a sample of butter. After shaking with ethanol and adding cold water, a cloudy white emulsion formed. What does this result indicate?

29.A sample of DNA has the base sequence A C G T on one strand. What is the sequence on the complementary strand?

30.Which of the following is the basic unit of a carbohydrate?

31.All proteins are made from long chains of amino acids.

32.Which food test uses ethanol and cold water to detect the presence of lipids?

33.DNA is made up of nucleotides that contain a phosphate, a deoxyribose sugar, and a base.

34.Which of these is a polysaccharide?

35.What colour change indicates a positive result for the Benedict's test for reducing sugars?

36.Put the following in order of size from smallest to largest: amino acid, protein, gene, nucleus.

37.Match each food test to the correct positive result.

38.Complete the sentence about DNA base pairing.

39.Name the two types of molecule that make up the 'backbone' of a DNA strand.

40.Describe how you would test a food sample for the presence of protein. Include the reagent used, the method, and the positive result.