Select your language

Suggested languages for you:
Log In Start studying!
StudySmarter - The all-in-one study app.
4.8 • +11k Ratings
More than 3 Million Downloads
Free
|
|

All-in-one learning app

  • Flashcards
  • NotesNotes
  • ExplanationsExplanations
  • Study Planner
  • Textbook solutions
Start studying

Fatty Acids

Save Save
Print Print
Edit Edit
Sign up to use all features for free. Sign up now
Fatty Acids

Fatty acids, along with glycerol, are building blocks of lipids in our bodies and food. The first thing that comes to your mind when you read fatty acids may be that they are fat or made of fat. They are, in fact, the building blocks of fats and other lipids such as waxes. The structure of fatty acids allows for the different types to emerge: saturated and unsaturated fatty acids.

Fatty acids are acids belonging to the carboxylic acid group, meaning they consist of a carboxyl group ⎼COOH (carbon-oxygen-hydrogen).

The structure of fatty acids

Fatty acids are, like the lipids that they build, organic molecules. This means they contain carbon and hydrogen. They contain oxygen as well.

They are often referred to as long molecules, as they consist of a long, straight chain of carbon and hydrogen atoms, with a carboxyl acid group (―COOH) at one end and a methyl group at the other. The simple formula is RCOOH, where R is the hydrocarbon chain, including the methyl group. The R-group may be saturated or unsaturated.

In addition, fatty acids can vary in terms of the length of the hydrocarbon chain (12 to 20 carbon atoms).

The sheer length of the hydrocarbon chain means that there are many carbon and hydrogen atoms but far fewer oxygen atoms as a part of the COOH. This makes these fatty acids hydrophobic.

The two types of fatty acids

There are two different types of fatty acids: saturated and unsaturated.

Saturated fatty acids

Saturated fatty acids have only single bonds between carbon atoms in the hydrocarbon chain. As you already know, carbon can form four bonds with other atoms. You also know that the hydrocarbon chain is composed of carbon atoms, to which hydrogen atoms attach. They attach to two of the four bonds of carbon atoms. This means that there are a lot of hydrogen atoms attached to each carbon, so you can say that there is a maximum number of hydrogen atoms in the chain and that the fatty acid is saturated with hydrogen.

Saturated fatty acids are primarily present in food and products from animal sources, such as beef, lamb, butter, cream, etc., and oils derived from plant sources, such as coconut and palm oil.

They are solid at room temperature because the hydrocarbon chain is straight, which in turn allows molecules of saturated fatty acids to pack closely together.

The most common saturated fatty acid is palmitic acid.

Figure 1

Unsaturated fatty acids

Unsaturated fatty acids have single bonds between carbon atoms but double bonds as well. As there are double bonds between some carbon atoms in the hydrocarbon chain, not as many hydrogen atoms can attach to carbon atoms. So you can say that these fatty acids are not saturated or unsaturated with hydrogen.

Double bonds make them liquid at room temperature. As they cause the molecule to bend, they prevent unsaturated fatty acids from packing together as closely as saturated fatty acids.

Depending on how many double bonds are present, there are two different types: mono-unsaturated and poly-unsaturated.

Mono-unsaturated fatty acids

Mono-unsaturated fatty acids have only one double bond between two carbon atoms in the hydrocarbon chain.

Figure 2

Poly-unsaturated fatty acids

Poly-unsaturated fatty acids have two or more double bonds between carbon atoms in the hydrocarbon chain.

Figure 3

Essential fatty acids

In your lipids and fatty acids studies, you will undoubtedly come across essential fatty acids. They are called essential because they are extremely important for our health, especially the heart and the brain, but they cannot be synthesized (made) by our body. Therefore, we need to consume food high in essential fats: fish and other seafood, seeds such as hemp and pumpkin seeds, leafy vegetables, etc.

In humans, there are two: alpha-linolenic acid or ALA and linoleic acid or LA.

ALA is an omega-3, while LA is an omega-6 fatty acid. Both are poly-unsaturated.

Two other omega-3 acids are of great importance for our bodies: eicosapentaenoic (EPA) and docosahexaenoic (DHA). Our bodies can produce these by converting the ALA but in a very limited amount.

The names are quite complicated, and you are not required to learn them by heart. They are mentioned here only to familiarise you with the acronyms ALA, LA, EPA, and DHA.

You may wonder why these acids are called omega-3 and omega-6. This is because, in the long hydrocarbon chain, the carbon atoms are numbered 1, 2, 3, etc. They are numbered starting from the end that has the methyl group. The last letter of the Greek alphabet, the omega (ω), is used to indicate the double bonds in the chain.

The similarities and differences between saturated and unsaturated fatty acids

Fatty AcidsSaturatedUnsaturated
mono-unsaturatedpoly-unsaturated
Structure
Long hydrocarbon chain with a methyl group + a carboxyl group = RCOOH
Long hydrocarbon chain with a methyl group + a carboxyl group = RCOOH
Long hydrocarbon chain with a methyl group + a carboxyl group = RCOOH
Hydrocarbon chainstraightbentbent
Bondssingle bondsone double bondmultiple double bonds
State at room temperaturesolidliquidliquid
Visual of the structure

Figure 1

Figure 2

Figure 3

Fatty Acids - Key takeaways

  • Fatty acids are, along with glycerol, building blocks of lipids.

  • Fatty acids consist of a long, straight chain of carbon and hydrogen atoms, with a carboxyl acid group (―COOH) at one end and a methyl group CH3 at the other. The simple formula is RCOOH, where R is the hydrocarbon chain. The R-group may be saturated or unsaturated.

  • Saturated fatty acids have only single bonds between carbon atoms in the hydrocarbon chain. These acids are solid at room temperature. A straight hydrocarbon chain allows for them to pack together closely.

  • Unsaturated fatty acids have single bonds between carbon atoms but double bonds as well. They are liquid at room temperature due to the bend in the hydrocarbon chain caused by double bonds.

  • Mono-unsaturated fatty acids have only one double bond between two carbon atoms in the hydrocarbon chain. Poly-unsaturated fatty acids have two or more double bonds between carbon atoms in the hydrocarbon chain.

  • Essential fatty acids are extremely important for our health, especially the heart and the brain, but they cannot be synthesised (made) by our body. Alpha-linolenic acid or ALA and linoleic acid or LA are essential fatty acids. ALA is an omega-3, while LA is an omega-6 fatty acid.

Frequently Asked Questions about Fatty Acids

Fatty acids consist of a long, straight chain of carbon and hydrogen atoms, with a carboxyl acid group (―COOH) at one end and a methyl group -CH3 at the other.

The three main types of fatty acids are saturated, mono-unsaturated, and poly-unsaturated.

Fatty acids are used for the formation of lipids. They are building blocks of lipids, which are essential biological macromolecules. 

Palmitic acid (saturated), alpha-linolenic acid or ALA (omega-3) and linoleic acid or  LA (omega-6).

Essential fatty acids are polyunsaturated fatty acids vital for our health, especially the heart and the brain, but they cannot be synthesised (made) by our body. Therefore, we need to consume food high in essential fats: fish and other seafood, hemp and pumpkin seeds, leafy vegetables, etc. In humans, there are two: alpha-linolenic acid or ALA and linoleic acid or LA. ALA is an omega-3, while LA is an omega-6 fatty acid. Two other omega-3 acids of great importance for our bodies are: eicosapentaenoic (EPA) and docosahexaenoic (DHA). 

Final Fatty Acids Quiz

Question

What is the definition of fatty acids?

Show answer

Answer

Fatty acids are, along with glycerol, building blocks of lipids. They are acids belonging to the carboxylic acid group, meaning they consist of a carboxyl group ⎼COOH (carbon-oxygen-hydrogen).

Show question

Question

Why are fatty acids referred to as long molecules?

Show answer

Answer

 Fatty acids are referred to as long molecules because they have a long, straight chain of carbon and hydrogen atoms.

Show question

Question

Are fatty acids hydrophobic?

Show answer

Answer

Yes, fatty acids are hydrophobic, which means they are insoluble in water.

Show question

Question

What are the two different types of fatty acids? Fill in the gaps:

There are two different types of fatty acids: s_______ and u_________.

Show answer

Answer

Saturated and unsaturated.

Show question

Question

What kind of bonds do saturated fatty acids have between carbon atoms?

Show answer

Answer

Saturated fatty acids have single bonds between carbon atoms.

Show question

Question

Why do we say that this type of fatty acid is saturated?


Show answer

Answer

We say they are saturated with hydrogen atoms, as hydrogen atoms attach to two of four bonds of carbon atoms.

Show question

Question

Are saturated fatty acids solid or liquid at room temperature?

Show answer

Answer

Solid

Show question

Question

What kind of bonds do unsaturated fatty acids have between carbon atoms?

Show answer

Answer

Unsaturated fatty acids have single and double carbon-carbon bonds.

Show question

Question

Why do we say that some fatty acids are unsaturated?

Show answer

Answer

It is because unsaturated fatty acids have fewer hydrogen atoms as there is only one bond per double-bonded carbon atom, instead of two bonds, to which they can attach. We can say that these fatty acids are unsaturated with hydrogen.

Show question

Question

Why are unsaturated fatty acids liquid at room temperature?

Show answer

Answer

Unsaturated fatty acids are liquid at room temperature because the double bonds cause the molecule to bend, which prevents molecules from packing together as closely as saturated fatty acids.

Show question

Question

Depending on how many double bonds in an unsaturated fatty acid, what are the two different types?

Show answer

Answer

Mono-unsaturated and poly-unsaturated fatty acids.

Show question

Question

How many double bonds between carbon atoms does a mono-unsaturated fatty acid have? 

Show answer

Answer

A mono-unsaturated fatty acid has one double bond.

Show question

Question

How many double bonds are there in a poly-unsaturated fatty acid?

Show answer

Answer

There are two or more double bonds in poly-unsaturated fatty acids.

Show question

Question

What are the two essential fatty acids?

Show answer

Answer

Alpha-linolenic acid or ALA and linoleic acid or LA.

Show question

Question

Fill in the gaps. Chose from the options below. 


All fatty acids have ________. The hydrocarbon chain in saturated fatty acids is ______ and in unsaturated it is _____.

Monounsaturated fatty acids have ______ and polyunsaturated have _______ in the hydrocarbon chain.

Saturated fatty acids are ________ and unsaturated __________ at room temperature. 


  • two or more double bonds
  • a long hydrocarbon chain with a methyl group + a carboxyl group =RCOOH
  • one double bond
  • bent
  • liquid
  • solid
  • straight 

Show answer

Answer

All fatty acids have a long hydrocarbon chain with a methyl group + a carboxyl group =RCOOH.

The hydrocarbon chain in saturated fatty acids is straight and in unsaturated it is bent.

Monounsaturated fatty acids have one double bond and polyunsaturated have two or more double bonds in the hydrocarbon chain.

Saturated fatty acids are solid and unsaturated are liquid at room temperature.

Show question

60%

of the users don't pass the Fatty Acids quiz! Will you pass the quiz?

Start Quiz

Discover the right content for your subjects

No need to cheat if you have everything you need to succeed! Packed into one app!

Study Plan

Be perfectly prepared on time with an individual plan.

Quizzes

Test your knowledge with gamified quizzes.

Flashcards

Create and find flashcards in record time.

Notes

Create beautiful notes faster than ever before.

Study Sets

Have all your study materials in one place.

Documents

Upload unlimited documents and save them online.

Study Analytics

Identify your study strength and weaknesses.

Weekly Goals

Set individual study goals and earn points reaching them.

Smart Reminders

Stop procrastinating with our study reminders.

Rewards

Earn points, unlock badges and level up while studying.

Magic Marker

Create flashcards in notes completely automatically.

Smart Formatting

Create the most beautiful study materials using our templates.

Sign up to highlight and take notes. It’s 100% free.