Biology 9700 · AS & A Level · Testing for biological molecules

Testing for biological molecules — practice question

The olive plant, Olea europaea, is cultivated in many regions of the world. Its fruits (olives) and the oil obtained from them (olive oil) provide food for humans. Triglycerides are the main lipid type in olive oil. They are made in the olive plant from glycerol and fatty acids. Scientists can examine samples of different olive oils to determine: - the fatty acids used to make the triglycerides - the composition of the different triglycerides present.
(a(i))[1]

Table 1.1 gives the C:D value for oleic acid. In Table 1.1, enter the values for D for each of the other four fatty acids shown.

(a(ii))[1]

Within the first column of Table 1.1, place a circle around every fatty acid that is saturated.

(a(iii))[1]

State which part of the chemical structure, labelled X, is missing from Table 1.1.

(a(iv))[2]

The analysis of the triglycerides in the different olive oil samples showed that: - olive oil contains many different triglycerides - the composition of each olive oil is different, but the same few triglycerides occur in all olive oils. Using Table 1.1 and the structure of triglycerides, suggest explanations for these findings.

(b)[2]

Glycerol dissolves in water. Triglycerides do not dissolve in water. Explain why water is a good solvent for some substances such as glycerol, but a poor solvent for substances such as triglycerides.

(c)[1]

Phloem is the plant tissue that transports organic substances, such as fatty acids, from one part of a plant to another. It consists of more than one cell type. Name the type of cell that forms the transport vessels of phloem tissue.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: The correct double-bond numbers for each fatty acid are: palmitic acid $0$, linoleic acid $2$, stearic acid $0$, palmitoleic acid $1$

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