The key difference between cis and trans fat is that in cis fats, the two H atoms are present on the same side of the double bond while in trans fats, two H atoms are present on the opposite sides of the double bond.
Fats or fatty acids are carboxylic acids comprised of a straight chain of an even number of carbon atoms, with hydrogen atoms along the length of the chain and a carboxyl group at the other end. These long aliphatic chains are either saturated or unsaturated. Saturated fatty acids do not have carbon-carbon double bonds, while unsaturated fatty acids have double bonds between carbon atoms. When a double bond occurs in the middle of the chain, it can either be cis or trans. In cis fats, the double bond forms with the two hydrogen atoms on the same side of the double bond. In trans fats, the double bond forms with the two hydrogen atoms on opposite sides of the double bond.
CONTENTS
1. Overview and Key Difference
2. What is Cis Fat
3. What is Trans Fat
4. Similarities Between Cis and Trans Fat
5. Side by Side Comparison – Cis vs Trans Fat in Tabular Form
6. Summary
What is Cis Fat?
Cis fat is a form of unsaturated fatty acids. In cis fats, two hydrogen atoms are on the same side of the double bond of the fatty acid’s carbon chain backbone. Cis fats are bent chains. Therefore, they are less stable compared to trans fats. Moreover, cis bonds form high energy configuration. During hydrogenation, some of the cis bonds in fatty acids are transformed into trans bonds, resulting in trans fatty acids.
Figure 01: Cis and Trans Fat
What is Trans Fat?
Trans fats or trans fatty acids are a type of unsaturated fatty acids. In trans fats, two hydrogen atoms are found on opposite sides of the double bond of the fatty acid’s carbon chain backbone. Therefore, in trans fats, each end of the double bond will have a single hydrogen atom sticking off to the side. In comparison to cis fats, trans fats are stable, and they help to preserve foods. Trans fats occur naturally only to a small degree. Hence, they are created through hydrogenation. Milk, butter and meat contain naturally occurring trans fats while doughnuts, cakes, pie crusts, frozen foods such as pizza, cookies, crackers, stick margarine, peanut butter, dairy creamers, powdered sauces and dressings and powdered hot cocoa contain artificial trans fats.
Figure 02: Trans Fat Foods
Trans fats contribute to the increase of low-density lipoprotein cholesterol, which can increase the risk of cardiovascular diseases. Hence, it is necessary to minimize the intake of trans fats.
What are the Similarities Between Cis and Trans Fat?
- Cis and trans fat are two subtypes of fatty acids.
- They have the exact same molecular structure.
- Their number of carbon, hydrogen and oxygen atoms are the same and in the same order.
- They have a double bond in the middle of the molecule.
- During the process of hydrogenation, some cis bonds in fatty acids are transformed into trans bonds, resulting in trans fatty acids.
- Saturated fatty acids have higher melting points than both trans and cis fatty acids
What is the Difference Between Cis and Trans Fat?
Cis fats have two hydrogen atoms on the same side of the double bond. Trans fats have two hydrogen atoms on the opposite sides of the double bond. So, on the chemical aspect, this is the key difference between cis and trans fat. Moreover, another important difference between cis and trans fat is that trans fats are thermodynamically more stable than cis fats. Furthermore, trans fats have a higher melting point than cis fats.
Below infographic shows more differences between cis and trans fat in tabular form for side by side comparison.
Summary – Cis vs Trans Fat
Cis and trans fats are two forms of unsaturated fatty acids. In cis fats, two hydrogen atoms are on the same side of the double bond. Therefore, the cis bond forms a bent chain. In trans fats, two hydrogen atoms are on the opposite sides of the double bond. Moreover, a trans bond forms a straight chain. Trans fats are geometric isomers of cis fats. Thus, this is the summary of the difference between cis and trans fat.
Reference:
1. Marchand, V. “Trans Fats: What Physicians Should Know.” Paediatrics & Child Health, Pulsus Group Inc, July 2010, Available here.
Image Courtesy:
1. “Cis trans” (CC BY 2.5) via Commons Wikimedia
2. “2253349” (CC0) via Pixabay