Home Economics Revision

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  • Topic: Fatty acid, Fat, Fatty acids
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  • Published : May 27, 2013
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Revision Questions – Nutrients
Lipids
1. Lipids are made up of 3 fatty acids and a glycerol molecule, referred to as a triglyceride. Glycerol is an alcohol with 3 hydroxyl groups (OH). A fatty acid attaches itself to each hydroxyl group with the elimination of 3 water molecules (condensation). The fatty acids vary and determine the properties of a lipid.

2. Saturated fatty acids:
* Each carbon has a full quota of hydrogen atoms.
* There are no double bonds.
* Solid at room temperature.
* Generally from animal sources (e.g.) butyric acid (butter). Mono-unsaturated fatty acids:
* All carbon atoms are not saturated with hydrogen.
* There is one double bond.
* Soft/liquid at room temperature.
* Generally come from plant sources and fish (e.g.) oleic acid (corn oil).

Polyunsaturated fatty acids:
* All carbon atoms are not saturated with hydrogen.
* More than one double bond (many).
* Generally soft/liquid at room temperature.
* Generally from plant sources and fish (e.g.) linoleic acid (2 double bonds), linolenic acid (3 double bonds) and arachidonic acid (4 double bonds).

3. (i) Essential fatty acids: Cannot be manufactured by the body, therefore they must be obtained from food. The polyunsaturated fatty acids, linoleic, linolenic and arachidonic acids, are referred to as essential fatty acids. Linoleic is the most important because linolenic and arachidonic acids can be synthesized from linoleic acid. They are essential for growth and also counteract the hardening effect of cholesterol on the arteries. (ii) Cis- and Trans-Fatty Acids:

* Polyunsaturated fatty acids are called cis-fatty acids when the hydrogen atoms on either side of the double bonds are both above or below the carbon chain. * Polyunsaturated fatty acids are called trans-fatty acids when the hydrogen atom on either side by the double bond are on opposite sides of the carbon chain. (LDL deposits cholesterol on the walls of the...
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