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Fat

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Fat is a fundamental biological substance found in almost all living beings. In chemistry and biology, fat refers to any ester of fatty acids. It is often used as a synonym for lipids. Lipids are substances that are insoluble in water but soluble in non-polar solvents. Fats are one of the three main macronutrient groups in the human diet. The other two groups are carbohydrates and proteins. Fats serve as a very dense source of energy for animals. One gram of fat provides about nine food calories when metabolized. This is more than twice the energy found in one gram of carbohydrates, which provides about four calories.

Fat triglyceride shorthand formula
Fat triglyceride shorthand formula

The most common type of fat is the triglyceride. A triglyceride is a molecule formed from one glycerol and three fatty acids. This occurs through a process called esterification. In this condensation reaction, the fatty acids connect to the glycerol. This connection forms an ester bridge and eliminates a water molecule.

Trimyristin-3D-vdW
Trimyristin-3D-vdW

Other types of lipids include monoglycerides and diglycerides. These have only one or two fatty acids attached to the glycerol. There are also phospholipids, which have a phosphoric acid group instead of a third fatty acid. Some lipids, like sterols or cholesterol, belong to this broader category of biological substances.

Fat triglyceride shorthand formula
Fat triglyceride shorthand formula

Digesting fat is a complex, multi-step process that happens in the intestines. When you eat fat, the body must break it down to absorb it. The pancreas secretes enzymes called lipases into the intestine. These lipases act on the ester bonds of the triglycerides. This process is known as lipolysis. Lipolysis splits the triglycerides into free fatty acids and monoacylglycerols. Once broken down, these pieces move into the absorptive enterocyte cells. These cells line the intestines. Inside the enterocytes, the body rebuilds the triglycerides. It then packages them with cholesterol and proteins into carriers called chylomicrons.

Fat composition in foods
Fat composition in foods

After they are built, chylomicrons are released from the cells. They enter the lymph system and travel toward the large vessels near the heart. Eventually, they mix into the bloodstream. Different tissues can then capture these chylomicrons to use the fat for energy. Triglycerides cannot pass through cell membranes on their own. Specialized enzymes called lipoprotein lipases on the blood vessel walls must break them down. This releases the fatty acids and glycerol. These components are then taken up by cells using fatty acid transport proteins, or FATPs.

Blood values sorted by mass and molar concentration
Blood values sorted by mass and molar concentration

Animals use adipose tissue to store metabolic energy for long periods. Adipose tissue is also known as fatty tissue. It contains specialized cells called adipocytes. These cells store fat that comes from the diet or from the liver. When the body experiences energy stress, these cells degrade their stored fat. This supplies fatty acids and glycerol to the circulation. This process is regulated by hormones like insulin, glucagon, and epinephrine. Adipose tissue also secretes a hormone called leptin.

Fatmouse
Fatmouse

Fat also provides thermal insulation and protects organs from shock. It can even act as a buffer against diseases by diluting unsafe substances in the blood.

Dietary fats are categorized by their chemical structure into saturated and unsaturated fats. Animal products like beef, butter, and cheese mostly contain saturated fatty acids. Plant oils like olive oil, avocado, and nuts generally contain more unsaturated acids. Some plants, like coconut and palm kernel oil, are exceptions.

Fatchart
Fatchart

The human body cannot produce all the fats it needs. It must consume two essential fatty acids: alpha-linolenic acid and linoleic acid. These are vital for health. Many health organizations, including the World Health Organization, suggest replacing saturated fats with unsaturated fats. This can reduce the risk of cardiovascular diseases and diabetes.

Margaryn 022
Margaryn 022

Nutritionists often study different dietary patterns, such as the Mediterranean diet. This diet includes more total fat than Northern European diets. However, it focuses on unsaturated fats from fish and olive oil. Studies suggest this diet may reduce the risk of cancer and neurodegenerative diseases. While some suggest avoiding saturated fats entirely, others warn against replacing them with refined carbohydrates. This is because refined carbohydrates carry a high risk of obesity and heart disease. Understanding the balance of these fats is a key part of modern nutritional science.

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🖼️ Images & Media (9)
File:Trimyristin-3D-vdW.png
Trimyristin-3D-vdW.png
File:Fat composition in foods.svg
Fat composition in foods.svg
File:Fatmouse.jpg
Fatmouse.jpg
File:Fat triglyceride shorthand formula.svg
Fat triglyceride shorthand formula.svg
File:Fatchart.svg
Fatchart.svg
File:Fat triglyceride shorthand formula.PNG
Fat triglyceride shorthand formula.PNG
File:Margaryn 022.jpg
Margaryn 022.jpg
File:Crisco Cookbook 1912.jpg
Crisco Cookbook 1912.jpg
File:Blood values sorted by mass and molar concentration.png
Blood values sorted by mass and molar...
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