A kind of molecule
Are hydrocarbons rare?
Nope. Both carbon and hydrogen were common in nebulae, in exploded stars. So hydrocarbon molecules are very common in space. Many of these molecules are small, like methane. But others are very big. Many hydrocarbons involve hundreds of atoms. Carbon atoms hook together easily. So carbon can easily make long chains of carbon atoms. It’s easy for big molecules to form using carbon as a building block.
One protein molecule can include hundreds of amino acids. They hook together in many different ways, even in the same molecule.
All living cells are made out of those protein molecules. So all living cells are also made out of hydrocarbons. That includes your body, fish, sweet potatoes, and trees. It includes cheese, and seaweed. All those things are made of hydrocarbon molecules.
Anything that was once alive is also made of hydrocarbons. That includes things like oil (made out of plants that died billions of years ago), gasoline and plastic (made out of oil). It also includes rubber, wood, food, alcohol, and many medicines like antibiotics.