Fat cells are the basic building blocks of adipose tissue. Fat (or fat) Tissue is found throughout the human body and is concentrated under the skin, between muscles, and around internal organs.

The main functions of fat cells are to store lipids for energy, to produce and secrete hormones, and to release thermal energy from lipids.

Fat cells are the basic units of adipose tissue
What are the functions of fat cells?

What are fat cells?

Fat cells (AKA Adipocytes or Fat cells) are the cells that make it up Adipose tissue. Their main functions are to store energy in the form of Lipids and create an insulating layer under the skin to maintain body heat. Adipose tissue isolates, cushions and protects the internal organs as well.

Where are fat cells found?

Fat cells are mainly located under the skin, between muscles, and around internal organs. Adipose tissue under the skin is known as subcutaneous fat, and it acts mainly as an insulating layer and energy storage. Fat tissue between the muscles and the internal organs is called visceral fat. Visceral fat also helps isolate the body and prevent heat loss, while acting as a shock absorber to cushion and protect the organs.

Fat cells are found in many parts of the human body
Subcutaneous fat is under the skin; visceral fat surrounds the internal organs

Types of fat cells

There are three main types of adipocytes in vertebrates; There are white fat cells, brown fat cells, and beige fat cells. Different types of fat cells are found in different regions of the body and have different functions in relation to each other.

White fat cells

Most of the fat in the human body is white adipose tissue. White fat cells are highly specialized in fat storage and contain large lipid droplets. Because of this, they act as the body’s main reserve of energy.

White adipose tissue also makes up most of the insulating layer that lies under the skin and surrounds the internal organs. This layer is important for maintaining body heat and thus for regulating body temperature.

There are three types of fat cells in the human body
Adipocytes can be brown, beige, or white

Brown fat cells

Brown adipose tissue also stores energy, but unlike white fat cells, brown fat cells specialize in releasing energy in the form of heat. This process (known as Thermogenesis) turns on in response to low outside temperatures and helps maintain body temperature in cold conditions.

Brown fat cells are typically smaller than white fat cells and may contain multiple small lipid droplets (instead of the single large droplet found in white adipocytes). They are also endowed with abundant mitochondria, which is what gives these cells their brown color. During thermogenesis, the mitochondria in brown fat cells convert the chemical energy stored in lipids into thermal energy. The heat is released from the fat cell and dissipated through the body tissue in order to maintain or increase the overall temperature.

Brown adipose tissue is found in certain regions of the body, including between the neck muscles and shoulder blades, along the spinal cord, above the collarbone, and sometimes around the internal organs.

Brown fat cells and white fat cells have different functions
Brown fat cells are smaller than white fat cells

Beige fat cells

Beige adipocytes are halfway between white and brown fat cells and have characteristics of both. Located in similar areas to white fat cells, they act like white adipocytes until activated by low temperatures. When this happens, they go through a process called “tanning” and begin to behave like brown adipocytes (that is, they begin to burn lipids for energy).

Function of fat cells

Adipocytes specialize in storing fat and function primarily as a reserve of fuel for the body. However, fat cells also have two other key functions, namely releasing hormones and generating heat.

Energy storage

White fat cells act as long-term energy stores and specialize in storing lipids in the form of Triglycerides. They are the body’s safety net against hunger and release fatty acids and glycerine as fuel for the rest of the body during times of fasting.

When we consume excess calories, our bodies store more fats and the size of the lipid droplets in fat cells increases. This gradually leads to an increase in the mass of adipose tissue and can contribute to obesity.

The storage and release of fatty acids by white blood cells is controlled by Hormones, as Insulin. The release of pancreatic insulin stimulates fat cells to take up and store triglycerides, while a drop in insulin levels causes fat cells to release their fatty acids.

Fat cells act as long-term energy stores
Fat cells are specially adapted to store triglycerides

Release of hormones

Adipose tissue is more than just an energy-storing mass. It also acts as a endocrine Organ, which means that it synthesizes and releases hormones. These hormones affect a variety of biological processes in the body, including regulating food intake and controlling insulin sensitivity.

Heat production

Like white adipocytes, brown fat cells store lipids for energy. However, they also have their own unique function, and this is thermogenesis: the use of lipids to generate heat.

Brown adipose tissue protects vertebrates from the cold and is “switched on” when exposed to low temperatures. When this happens, the abundant mitochondria in brown fat cells are triggered to increase their oxidation of fatty acids, a process that “wastes” chemical energy as heat. The heat generated by thermogenesis is dissipated via the tissue surrounding the brown fat cells and helps maintain the body temperature of the organism.

Brown fat cells have functions that go beyond storing energy
Brown fat cells use thermogenesis to generate heat

Structure of fat cells

Brown or white, all fat cells consist of a large lipid droplet surrounded by a thin layer of cytoplasm and a plasma membrane. Each cell also contains organelles, including a nucleus, Golgi apparatus, endoplasmic reticulum, ribosomes, and mitochondria. Brown fat cells contain many more mitochondria than white fat cells, which is what gives their lipid droplets their darker color.

The structure of a fat cell
Fat cells contain a large droplet of lipid


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