Lipogenesis is the process your body uses to convert carbohydrates into fatty acids, which are the building blocks of fats. Fat is an efficient way for your body to store energy.
Learn about the importance of acetyl-CoA and insulin in lipogenesis.
For your early ancestors, the ability to store fat was a wonderful thing because the ability to store fat meant survival during periods when food was scarce. Today, food is abundant, so this ability to store fat is not as appreciated as it once was. In fact, it’s an important factor in the obesity epidemic that haunts those of us living in the 21st century.Inside your body, fatty acids, which are basically the building blocks of fat, join together and form a type of fat known as triglycerides. Most of the fat on your body is stored as triglycerides, so when you pinch an inch around your midsection, you are essentially pinching triglycerides.
The fatty acids needed to make triglycerides come from digesting the fatty foods you eat, but they can also be made in your body from the carbohydrates you eat. This conversion of carbohydrates to fatty acids is the basis of lipogenesis. This is an easy term to recall if you remember that the prefix ‘lipo’ refers to lipid, which is another name for fat, and ‘genesis’ refers to creation, so lipogenesis is literally the process of lipid creation.
Unless you are following a low-carb diet, the bulk of your daily diet likely comes from carbohydrates. Carbohydrates are found in a lot of foods, like bread, pasta, vegetables and fruits. When you eat carbs, your body gets to work breaking them down into simple sugars, such as glucose, which easily passes into your bloodstream. The first thing your body will do with blood glucose is burn it up for energy.
Extra glucose that your body doesn’t need for immediate energy will go into storage. A small amount will be stored as glycogen, which is a stored form of glucose in your muscles and liver. Once this storage area is filled up, the remaining glucose gets converted to fat, which is essentially long-term energy storage.It is kind of like glucose is a car looking for a parking place. The first glucose cars that arrive get the best spots right up next to the action. The next group of cars has to park a bit farther away in the liver and muscles, the glycogen parking lot.
Whereas the last glucose cars to arrive need to travel to the long-term energy storage lot, known as body fat. And they have to travel to this long-term parking area via the lipogenesis access road. While it doesn’t seem convenient to make carbs go through this conversion so they can be stored as fat, your body doesn’t mind. In fact, it likes to store energy as fat because lipids can store more energy, or calories, per gram than carbohydrates. We see that every gram of fat contains 9 calories/gram, whereas carbohydrates only hold 4 calories/gram.
So believe it or not, fat is the most compact and efficient storage form when it comes to energy.
Lipogenesis takes place in the cytoplasm of your fat cells and liver cells. The process begins with acetyl-CoA, also referred to as acetyl coenzyme A, which is a molecule that is formed from the metabolism of glucose. The process proceeds with the help of fatty acid synthase, which is a complex of enzymes that catalyze the conversion of acetyl-CoA to fatty acid. This is a fairly easy term to recall if you break down the word ‘synthase.
‘ The prefix makes up part of the word synthesis, which means ‘making,’ and the suffix ‘ase’ is often used in biochemistry to indicate that the substances are ‘enzymes.’ Therefore, fatty acid synthase is literally ‘fatty acid making enzymes.’Insulin, which is a hormone produced in the pancreas, helps direct when lipogenesis should occur. Insulin is released when your body senses the presence of rising blood sugar, or blood glucose, levels. When you eat a big carbohydrate meal, you get a big insulin response, which tells your body there’s a lot of glucose molecules that need moved out of your blood, pronto.
Some of this glucose is burned, some is stored as glycogen, and the rest turns into fat. So we can say that insulin helps open up the doorway to lipogenesis and fat storage.
Let’s review. Fatty acids are the building blocks of fat. They join together to form triglycerides, which you think of as stored body fat.
Fatty acids can be made in your body through the process of lipogenesis, which is the conversion of carbohydrates to fatty acids.Carbohydrates that you eat get broken down into glucose, which is either burned or stored. Some is stored in your muscles and liver as glycogen, and the rest is converted via lipogenesis and stored as fat.Lipogenesis begins with acetyl-CoA, which is a molecule that is formed from the metabolism of glucose.
The process proceeds with the help of fatty acid synthase, which is a complex of enzymes that catalyze the conversion of acetyl-CoA to fatty acid. Lipogenesis is directed and regulated by insulin, which is a hormone produced in the pancreas.
After reviewing this lesson, you should have the ability to:
- Identify the function of fatty acids in the body
- Explain what happens to carbohydrates in the body
- Describe the process of lipogenesis and the role of acetyl-CoA and insulin in this process