Questions on Lipids

1. The structural formulas of some fatty acids can be found in Section 34 of the IB chemistry data booklet.

(a) Explain why linolenic acid is known as an omega-3 fatty acid.

(b) Describe the type of reaction taking place when propane-1,2,3-triol (glycerol) reacts with linolenic acid.

(c) Draw the structure of the triglyceride formed from glycerol and linolenic acid.

(d) State and explain whether this triglyceride is a solid or a liquid at room temperature.

(e) The triglyceride has the molecular formula C₅₇H₉₂O₆ and has a relative molecular mass of 873.5. What mass of the triglyceride will react exactly with 25.38 g of iodine?

2. (a) Explain why cholesterol (see Section 34 of the data booklet) is known as a steroid.

(b) Another steroid is estradiol.

Suggest a simple chemical test which you could use to distinguish between cholesterol and estradiol.

3. The diagrams show two different structures for linoleic acid.

Explain the basic difference between the two structures. The second one may be present in fried foods. Explain how it is formed and describe why it can be more hazardous to health than the first one.

Lipids questions