Introduction to Fatty Acid Metabolism

Summary

This lecture explores fatty acid metabolism, focusing on their role as fuel, membrane components, protein modifiers, and hormone precursors. It outlines the processes of fatty acid breakdown, which involves oxidation, hydration, and cleavage, ultimately generating ATP. The synthesis of fatty acids is the reverse, involving reduction, dehydration, and condensation, using activated acyl units and malonyl units to build longer chains. Understanding both breakdown and synthesis processes helps explain how cells regulate energy and construct essential biomolecules.

Takeaways

• 😀 Fatty acids are biological molecules consisting of a long hydrocarbon chain and a terminal carboxylate group, which gives them both hydrophobic and hydrophilic properties.
• 😀 Fatty acids serve four major roles in cells: as fuel molecules, building blocks for cell membranes, modifiers of proteins, and precursors for hormones.
• 😀 The breakdown of fatty acids involves four main steps: oxidation, hydration, oxidation again, and cleavage, which shorten the fatty acid chain by two carbons per cycle.
• 😀 The breakdown process extracts electrons through oxidation, forms double bonds, and results in the creation of acetyl-CoA units that enter the citric acid cycle to generate ATP.
• 😀 In fatty acid synthesis, the process is the reverse of breakdown, involving condensation, reduction, dehydration, and reduction again to elongate the fatty acid chain by two carbons per cycle.
• 😀 Fatty acid synthesis uses activated acetyl-CoA and malonyl-CoA units to build fatty acids, starting with a condensation reaction to join two-carbon units.
• 😀 The breakdown of fatty acids produces high-energy ATP molecules by using acetyl-CoA units in the citric acid cycle, contributing to cellular energy production.
• 😀 Fatty acids are oxidized during breakdown to generate energy, while they are reduced during synthesis to build larger molecules.
• 😀 The breakdown of fatty acids is an oxidative process that releases acetyl-CoA units, while synthesis is a reductive process that builds fatty acids from these units.
• 😀 Both fatty acid breakdown and synthesis involve cyclical steps, but the steps are mirror images of each other, with oxidation and reduction steps reversed.

Q & A

What are fatty acids and what key features do they have?

Fatty acids are biological molecules consisting of a long hydrocarbon chain and a terminal carboxylate group. The carboxylate group gives them hydrophilic (polar) properties, while the long hydrocarbon chain makes them hydrophobic (non-polar).

What are the four main functions of fatty acids in the body?

1. Fatty acids serve as fuel molecules for ATP generation. 2. They are used to build components of cell membranes, such as glycolipids and phospholipids. 3. Fatty acids can modify proteins, diversifying their functionality. 4. Fatty acids are used to synthesize hormones and other intracellular messenger molecules.

How does the process of fatty acid breakdown work?

Fatty acid breakdown occurs through a cycle consisting of four main steps: 1. Oxidation (removal of electrons, forming a double bond), 2. Hydration (adding a hydroxy group to the molecule), 3. Another oxidation (converting the hydroxy group to a carbonyl group), and 4. Cleavage (splitting the molecule to form acetyl-CoA units). Each cycle removes two carbon atoms from the fatty acid chain.

What is the role of coenzyme A in fatty acid breakdown?

Coenzyme A attaches to the fatty acid to activate it, making it more reactive and ready for the oxidation process. It also participates in the cleavage step, where it helps split the fatty acid into two-carbon acetyl-CoA units.

What happens to the acetyl-CoA units produced during fatty acid breakdown?

The acetyl-CoA units enter the citric acid cycle (Krebs cycle), where they are used to generate ATP, which is a high-energy molecule used by cells for various processes.

What are the key differences between fatty acid breakdown and synthesis?

Fatty acid breakdown is an oxidative process that shortens the fatty acid chain by two carbons per cycle, while fatty acid synthesis is a reductive process that lengthens the fatty acid chain by two carbons per cycle. The two processes are mirror images of each other, with breakdown involving oxidation and synthesis involving reduction.

What is the first step in fatty acid synthesis, and how does it differ from breakdown?

The first step in fatty acid synthesis is a condensation reaction between activated acetyl-CoA and malonyl-CoA units, which forms a new carbon-carbon bond. This is the opposite of the first step in fatty acid breakdown, which is oxidation (removing electrons to form a double bond).

How does the reduction process play a role in fatty acid synthesis?

During fatty acid synthesis, after condensation, a reduction step occurs where the ketone group in the molecule is converted into an alcohol group by adding electrons and hydrogen atoms. This is the reverse of the oxidation step in breakdown.

What is the role of dehydration in fatty acid synthesis?

In fatty acid synthesis, after the reduction step, a dehydration reaction removes a water molecule, forming a double bond. This is the opposite of the hydration step in fatty acid breakdown, where a hydroxy group is added.

Why is fatty acid metabolism essential for the body?

Fatty acid metabolism is essential because it provides energy (ATP) through breakdown, supports the construction of cellular structures (such as membranes), aids in protein modification, and is involved in hormone and intracellular signaling molecule synthesis.