Biological Molecules (Cambridge (CIE) IGCSE Biology)

This 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.

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. 

Table 1 contains some statements about biological molecules.

Table 1

Place ticks (✓) in Table 1 to indicate statements that apply to carbohydrates.

Compare the chemical elements found in carbohydrates and proteins.

Fig. 1 shows the structure of glucose.

Fig. 1

Fig. 2 shows the structure of another sugar.

Fig. 2

Identify the sugar depicted in Fig. 2. Explain your choice of answer.

Fig. 3 shows groups of biological molecules and the building blocks that make them up.

Fig. 3

Join the boxes in an appropriate manner using straight lines. 

Fig. 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

Fig. 2 shows the chemical structure of an amino acid called serine.

Fig. 2

(i)

 Draw a label line to indicate serine's central carbon with an X on Fig. 2.

[1]

(ii)  

Draw a line around the R group of serine on Fig. 2.

[1]

Table 1 contains some statements about the fate of proteins in an animal's body.

Table 1

Place these events into a logical chronological order.

Describe the test that would be used to show a positive result for the presence of protein in a sample of food.

Extended only

State the type of bonding that holds DNA bases together in base pairs. 

Extended only

Fig. 1 shows the base sequence on one strand of DNA. 

Fig. 1

Complete Fig.1 to show the base sequence of the opposite strand of DNA.

Extended only

Fig. 2 shows outlines that represent the bases of DNA.

Fig. 2

Use your knowledge of base-pairing to label each one with the letter that each could represent.

Note: there is more than one possible correct answer. 

The following are all aspects of the structure and organisation of an organ such as the liver.

• Chromosome

• Tissue

• Base

• DNA double helix

• Nucleus

• Cell

• Nucleotide

Using an imaginary powerful microscope with a full zoom function, list the order in which the above structures would become visible when zooming in on a piece of liver tissue. 

Table 1 shows four samples of food that were tested for glucose (reducing sugar) using the Benedict's test. 

Table 1

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. 

Explain the purpose of the test tube containing just water in the experiment shown in Fig. 1.

Explain why the test for lipids is known as an emulsion test.

Predict the colour changes (if any) of the iodine test on the food samples shown in Table 2.

Table 2