What is the Difference Between Choline and Acetylcholine

The main difference between choline and acetylcholine is that choline is a nutrient present in animals and plants, whereas acetylcholine is a neurotransmitter present in animals.

There is a significant difference between these two chemical compounds in terms of mass, chemical formula, structure, occurrence, uses, and properties. However, choline is a precursor for acetylcholine.

Key Areas Covered  

1. What is Choline 
     – Definition, Structure, Function
2. What is Acetylcholine
     – Definition, Structure, Function
3. Relationship Between Choline and Acetylcholine
     – Outline of Common Features
4. Difference Between Choline and Acetylcholine
     – Comparison of Key Differences

Key Terms

Choline, Acetylcholine

What is Choline

Choline is an essential nutrient present in animals and plants. It is also available as a dietary supplement. Choline is neither a vitamin nor a mineral, but it is an organic compound that is water-soluble. The molecular formula of choline is C₅H₁₄NO. Its molar mass is 104.1708 g/mol. Choline provides methyl groups which are needed for many steps in metabolic reactions. The liver produces choline as phosphatidylcholine in small quantities, but the body needs more choline. Hence, the required amount should be taken from outside. In fact, humans obtain the majority of choline from their diet.

The most common sources of choline in foods are sphingomyelin and phosphatidylcholine, which are fat-soluble phospholipids. Choline sources also include water-soluble compounds phosphocholine and glycerophosphocholine. It is also available as free choline. Mucosal and pancreatic enzymes release free choline from half of the fat-soluble forms and from some water-soluble forms. In the small intestine,  phosphocholine, glycerophosphocholine, and free choline get absorbed. After the absorption, they enter the liver and get stored there. Eventually, they get phosphorylated and distributed throughout the body to be used in making cell membranes. Plant cells and animal cells need choline to maintain their structural integrity of the cells. Another function of choline is to produce acetylcholine, which is a neurotransmitter. Choline is also associated with brain development in its early stages, lipid transport, lipid metabolism, cell membrane signalling, and modulating gene expression.

What is Acetylcholine

Acetylcholine is a chemical compound that functions as a neurotransmitter. The molecular formula of acetylcholine is C₇NH₁₆O₂+, and its IUPAC name is 2-Acetoxy-N,N,N-trimethylethanaminium. The molar mass of acetylcholine is 146.2074 g/mol. Acetylcholine is made up of two parts: acetyl coenzyme A and choline. A reaction between choline and acetyl coenzyme A with the help of choline acetyltransferase forms the acetylcholine molecules. They are made at the end of the nerve cells and are stored in the vesicles at the end of cholinergic neurons.

Acetylcholine is an excitatory neurotransmitter, exciting the nerve cells and causing the nerve cell to fire off messages. In fact, it is the main neurotransmitter of the parasympathetic nervous system, the part of the autonomic nervous system that dilates blood vessels and contracts smooth muscles. Acetylcholine exhibits inhibitory or excitatory responses due to its ability to block a response or stimulate a response.

Moreover, acetylcholine has numerous functions in the body. In motor neurons, it stimulates the contraction of muscles. Almost all movements in the body use acetylcholine as a neurotransmitter. It also plays a role in brain functions such as REM sleep, arousal, attention, and neuroplasticity. It also takes part in promoting a slower heart rate and increasing body secretions. As acetylcholine helps with movements in the body,  consuming drugs that affect acetylcholine can cause various movement disruptions and even paralysis. Disruption of acetylcholine may also lead to Alzheimer’s disease.

Relationship Between Choline and Acetylcholine

• Choline is a precursor for acetylcholine.
• In other words, a reaction between choline and acetyl coenzyme A in the body forms acetylcholine.

Difference Between Choline and Acetylcholine

Definition

Choline is a nutrient that is present in animals and plants, whereas acetylcholine is a neurotransmitter present in animals.

Molecular Formula

Choline has a molecular formula of C₅H₁₄NO, whereas acetylcholine has a formula of C₇NH₁₆O₂+.

Molar Mass

The molar mass of choline is 104.1708g/mol, while the molar mass of acetylcholine is 146.2074g/mol.

Function

Choline provides methyl groups necessary for many steps in metabolic reactions and produces acetylcholine. Meanwhile, acetylcholine is an excitatory neurotransmitter, exciting the nerve cells and causing the nerve cell to fire off messages.

Structure

Choline is an ethanolamine, whereas acetylcholine is an ester.

Conclusion

In brief, choline and acetylcholine differ according to the changes in their structures, functions, and properties. Choline is a precursor for acetylcholine. Acetylcholine acts as a neurotransmitter that is vital for the movements of the body. The main difference between choline and acetylcholine is that choline is a nutrient present in animals and plants, whereas acetylcholine is a neurotransmitter present in animals.

Reference:

1. “Acetylcholine.” PubChem. National Library of Medicine. 
2. “Choline.” PubChem. National Library of Medicine. 

Image Courtesy:

1. “Choline-skeletal” By NeuroFall2021 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Acetylcholine190” By Benjah-bmm27 – Own work (Public Domain) via Commons Wikimedia