Structure of cholesterol: What it is, function, and types – Medical News Today

Cholesterol is a waxy, fat-like substance that:

• is white or faint yellow
• is almost odorless
• has a solid rather than liquid consistency

The body needs cholesterol to maintain a person’s health, but only in limited amounts.

Although the liver makes its own cholesterol, people can also consume it through animal foods such as meat, poultry, fish, eggs, and dairy.

The body makes all the cholesterol it needs, so health experts recommend eating as little dietary cholesterol as possible. Research links diets with less cholesterol to a lower risk of cardiovascular disease.

The chemical formula of cholesterol is C₂₇H₄₆O. This means it consists of 27 atoms of carbon, 46 atoms of hydrogen, and one atom of oxygen.

Cholesterol’s structure consists of:

• a central sterol nucleus of four hydrocarbon rings, which are hydrogen and carbon atoms with a circular arrangement
• a hydrocarbon tail, a chain of hydrogen and carbon atoms at the end of a molecule
• a hydroxyl group, which is one hydrogen atom bonded to one oxygen atom

The four hydrocarbon rings join together in the middle of the compound. The hydrocarbon tail attaches to one end, and the hydroxyl group attaches to the other.

Both the sterol nucleus and hydrocarbon tail do not mix with water, so this structure cannot travel through the bloodstream alone. For this reason, cholesterol combines with proteins to create lipoproteins, which can travel through the blood to reach cells that need them.

Although people generally believe cholesterol is harmful, it has several important roles, including:

• A cell membrane component: Cholesterol is an important part of the cell membrane structure. It changes the fluid in the membrane, which can affect the internal cell environment. It also fosters transportation within the cell.
• A digestive aid: Cholesterol is a component of bile salt. The digestive system uses this to absorb fat-soluble vitamins A, D, E, and K.
• A precursor for important bodily substances: The body uses cholesterol to make:
  • vitamin D, which plays a role in bone health
  • steroid hormones, such as cortisol, which help the body respond to stress
  • reproductive system hormones such as estrogen and testosterone

Cholesterol also plays a role in the immune system and brain synapses. These are points of contact between nerve cells in the brain.

There are two primary types of cholesterol: low-density lipoprotein (LDL) and high-density lipoprotein (HDL). While people often refer to LDL as “bad” cholesterol, HDL is known as “good” cholesterol.

Most of the body’s cholesterol is LDL. High levels of LDL can cause fatty deposits called plaque to accumulate in the walls of blood vessels. Over time, this can cause the narrowing of the arteries, blocking blood flow and increasing a person’s risk of heart attack and stroke.

High LDL may stem from a combination of genetic factors and lifestyle habits.

Conversely, HDL reduces the buildup of plaque in blood vessels. It absorbs cholesterol and brings it to the liver, which removes it from the body.

Having high levels of HDL can reduce a person’s risk of a heart attack and stroke.

The structure of cholesterol consists of a central portion of four hydrocarbon rings that join together with a hydrocarbon tail on one end and a hydroxy group on the other. Because the structure does not mix well with water, proteins combine with cholesterol to form lipoproteins, allowing them to travel through the bloodstream.

While cholesterol serves essential functions, the body makes all that it needs. Therefore, experts recommend consuming as little dietary cholesterol as possible.