Now, in a saturated fat, the fatty acids have all single covalent bonds (Figure 9), all single lines between the H’s and the C’s, and, C's and C's. (Note: A carbon atom can only have four lines attached to it, Carbon atoms are tetravalent). This is named this way because no more hydrogen atoms can be added, the same way a sponge saturated with water- cannot hold anymore water.

Now when we deal with unsaturated fats (the poly unsaturated and mono unsaturated), it means that there is either one (mono) or several (poly) double bonds located between the carbon atoms somewhere along the Fatty Acid. The unsaturated likewise refers to the the ability of the fatty acids to hold more Hydrogen atoms (H), because each carbon only needs one bond between another carbon. Figure 10 is a section of a polyunsaturated fat, because there are two double bonds between separate carbons.

Trans fats are geometrically similar to those of the unsaturated fats. Trans fats do have double bonds that exist between the carbons as well. But the difference between the unsaturated fats and trans fats lie in the position of the surrounding hydrogen atoms. One is a “cis” configuration, and the other is a trans configuration. The “cis” configuration is when the hydrogen atoms of the joined carbons are on the same side, this configuration makes it a unsaturated fat. When the hydrogen atoms are on opposite sides, this is known as a “trans” configuration, hence the name, means it is a trans fat.

Notice how the cis configuration creates a bent line and the trans configuration a curved line. This difference in molecular shapes is what causes the mono- and polyunsaturated fats to remain liquid at room temperature, and the trans fat more solid at room temperature.

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