Because living things are made of chemicals and there are millions of chemical reactions taking place in the body every second. The majority of the body is made of water which is h2o ( hydrogen and oxygen) which are just simple molecules and elements. All cells and all living organisms are made of atoms.
All around us, living things or inorganic things are chemical compounds.
The study of the chemistry of living organisms is called organic chemistry.
Taxonomy is an important tool for better understanding the unity among living organisms because it helps to classify all living things. It tells the structural differences of organisms.
I believe the answer you are looking for is carbon. While it is not a molecule, Carbon is the focus of organic chemistry and is a major component of living things. The most important molecules in Biology are considered to be proteins, carbohydrates, nucleic acids, lipids and water, but they cannot be considered the focus of organic chemistry.
Chemical principles are important in modern cell biology because all living cells are made up of chemicals and many chemical processes occur in various living organisms. Chemistry is the one science in which all the other sciences are based. In biology you learn about living organisms and their composition. Organisms are alive because of chemistry - Why we breathe oxygen, how we make energy, elimination of waste products, cellular respiration, etc. All of these are based on how living organisms use chemistry to live.Biology is the study of biological organisms and processes. All biological organisms and processes are created, maintained and changed through chemical processes and are made up of chemical compounds. Without an understanding organic chemistry one cannot accurately and fully understand biology.
carbon
Various branches of science deal with non-living things, but you may be thinking of Chemistry - which is usually split into Organic Chemistry and Inorganic Chemistry. Inorganic would deal with the chemistry of non-living things.
organic chemistry
Carbon.
The study of Physical science is basicaly the study of non living things like earth science, chemistry, Astronomy, and physics
bones are important to living things because it protects plants
Oxygen is the most important factor for living things.