How does your body generate the heat for body temperature?


The energy to generate heat has to come from somewhere. Is it the friction of the blood pumping through the veins and tissues in your body? Is there some kind of chemical heat generation at the cellular level? Where does the heat come from?

In: 28

The heat comes from the energy in the food you eat. Your body burns calories to generate heat. You burn around 2000 calories a day just by existing.

We use the expression to “burn calories” for a reason: your cells are harnessing the very same combustion process as fire to turn the food you eat into energy. In addition to the chemical energy created by your cells in this reaction, thermal (heat) energy is also released.

Your body burns sugar to make energy, including heat. That’s not just a euphemism: the chemical process of converting sugar to energy is the same in your body as it is if you set it on fire. Sugar breaks down in the presence of oxygen to make carbon dioxide and energy.

Think of food as a mix of atoms that are bound together in ways that store energy. Your body breaks down the food, and captures some of the energy to do work (build other molecules, move things) but the rest of the energy is released as heat. When your body is cold, it can break down the food in such a way that more heat is released and less energy is captured to do work.

For example, sugar is a molecule made of carbon, hydrogen and oxygen. The way those atoms are joined together stores energy – especially the carbon-carbon connections (bonds) and the carbon-hydrogen connections. When the sugar is broken down, the products are carbon dioxide (CO2) and water (H2O). All of the carbon-carbon and carbon-hydrogen bonds have released their energy.

Ultimately, it is sunlight that heats the body, because sunlight is used in photosynthesis to convert water and carbon dioxide into sugars. Plants use energy from sunlight to create the complex energy storage molecules that we use for food.

Breaking the food down happens in every cell in your body, in the mitochondria. The food is first broken into small molecules in your stomach and intestine, and then the smaller molecules are transported through the blood to your cells. They can also be stored, for example as fat, for later use. Fats have lots of high energy carbon-carbon and carbon-hydrogen bonds.

Breaking down foods we eat releases energy, so does the breakdown of ANY molecule. the energy is stored in the chemical bonds and released.

In order for you to stay alive, our bodies constantly break and re-make this chemical called ATP. It’s used for literally everything. Every muscle contraction, for your heart to beat, every process your conscious mind isn’t aware of, all require the breakdown of ATP.

So we break down ATP and the energy released is used for many different things, including the manufacture of more ATP. (Breaking bonds releases energy, making bonds requires energy).

Our efficiency for using this energy is pretty bad. We only utilize roughly 30% of the energy released from the breakdown of an ATP. That remaining 70% is lost to heat