Question

If a bacterium uses beta-oxidation to catabolize a molecule of the fatty acid arachidic acid, which contains 20 carbon atoms, how many acetyl-CoA molecules will be generated?

Short answer

Given that the arachidic acid molecule is broken down into acetyl-CoA molecules naught by beta-oxidation, and considering that each acetyl-CoA molecule is made of two carbon atoms, then the total number of acetyl-CoA molecules that can be generated from one arachidic acid molecule is 20/2 = 10. So, 10 acetyl-CoA molecules will be produced.

Step-by-step solution

Understand the breakdown of fatty acids

Beta-oxidation is a chemical process where fatty acids are broken down into acetyl-CoA. The most crucial point to know is that each acetyl-CoA molecule has two carbon atoms.

Know the carbon number in arachidic acid molecule

Arachidic acid is made up of 20 carbon atoms.

Calculate the number of acetyl-CoA molecules

To find how many acetyl-CoA molecules will be created, divide the total number of carbon atoms in arachidic acid (20) by the number of carbon atoms present in each acetyl-CoA molecule (2). Therefore the equation is 20/2.

Key concepts

Fatty Acid Catabolism

Fatty acid catabolism refers to the process by which fatty acids are broken down in the body to generate energy. This process is crucial for providing energy to cells, especially during fasting or strenuous activities when glucose supplies might be low.

The primary pathway for fatty acid catabolism is known as beta-oxidation.
It's called "beta" because the reaction removes two carbon atoms from the beta position of the fatty acid chain and transforms them into acetyl-CoA.

This sequential removal occurs in a series of four key steps:

• Dehydrogenation: The fatty acid chain undergoes oxidation, removing two hydrogen atoms.
• Hydration: A molecule of water is added to the chain.
• Oxidation: Further removal of hydrogen atoms takes place.
• Thiolysis: The chain is split, releasing an acetyl-CoA unit while shortening the fatty acid chain.

This process is repeated cyclically, and each cycle produces one acetyl-CoA, reducing the fatty acid chain by two carbon atoms at a time.

Understanding fatty acid catabolism is essential as it highlights how the body taps into fat stores to supply continuous energy.

Arachidic Acid

Arachidic acid is a type of saturated fatty acid that is found naturally in peanut oil and other oils.
It has a chemical composition with 20 carbon atoms in its structure.

This makes it a long-chain fatty acid, and due to its saturation, it does not contain any double bonds between its carbon atoms.

Arachidic acid plays a role in the metabolism within organisms that can break it down for energy.
By undergoing beta-oxidation, arachidic acid is effectively reduced to shorter molecules that are crucial for various cellular functions.

Additionally, understanding the structure and metabolism of arachidic acid allows us to comprehend how different types of fats are processed and utilized in the body.

Acetyl-CoA Production

Acetyl-CoA is a pivotal molecule in metabolism, serving as a building block for numerous biochemical reactions in the cell.
It is produced not only from fatty acid catabolism but also from carbohydrates and protein breakdown.

During beta-oxidation, every two-carbon segment of a fatty acid is cleaved to generate one acetyl-CoA molecule. For arachidic acid, with its 20 carbon atoms, this means it can be entirely converted into acetyl-CoA units.

The math is straightforward:

• Arachidic acid has 20 carbon atoms.
• Since each acetyl-CoA contains 2 carbon atoms, dividing 20 by 2 gives us 10 acetyl-CoA molecules.

The acetyl-CoA thus produced is used in various pathways, most notably feeding into the citric acid cycle or Krebs cycle to generate ATP, which is the main energy currency of the cell. Understanding acetyl-CoA production is crucial for appreciating how the body efficiently converts stored molecules into usable energy.