Download What Are the Major Chemical Elements Found in

What Are the Major Chemical Elements Found
in Cells in Biology?
by David H. Nguyen, Demand Media
The Classroom » School Subjects » What Are the Major Chemical Elements Found in Cells in Biology?
The cells of living things are made mainly of four
elements: carbon, hydrogen, oxygen and nitrogen.
They make up 96% of the atoms that are in living
things, so they would be considered major
chemicals. However, depending on how you define
major, other elements that only make up a few
percent of cells can top the list. If major also
means essential for life, then “trace elements” are
very major though they make up just 0.5% of the
atoms in an organism.
Carbon atoms can link together to
form many shapes.
The Big Four
Carbon, hydrogen, oxygen and nitrogen are
known as the main “organic” elements because
they form the building blocks that make life
possible. Among the four, carbon is perhaps the
most special, since it can form bonds with itself
and makes molecules that have many different
shapes. Carbon molecules can be short chains, long
chains, bent chains, branching chains and ring
shapes. The four classes of macromolecules that
make life possible (protein, carbohydrates, lipids,
and nucleic acids) are all made of carbon, along
with the other three main organic elements.
Aside from the big four mentioned above, the next major elements would be
phosphorus, sulfur, sodium, chlorine, potassium, calcium and magnesium. These
make up 3.5% of living things. Phosphorus helps connect individual units of DNA
into a long chain. Sulfur forms bridges between different parts of a protein, which
help give the protein its 3D shape. Sodium, chlorine, potassium and calcium are
essential for nerve cells to send electrical signals to other cells. And some enzymes
require magnesium to work.
Trace Elements
Trace elements are present at low levels in organisms and make up just 0.5% of
living cells. However, living things would not be able to survive without trace
elements. Trace elements include iron, iodine, manganese, molybdenum,
selenium, silicon, tin, vanadium, boron, chromium, cobalt, copper and fluorine.
Iron is found in red blood cells and helps to carry oxygen in the blood stream.
Iodine is important for making different forms of thyroid hormone, which
regulates growth and energy levels in humans. Many of the trace elements are
required by enzymes in order to make chemical reactions happen.
The Importance of Water
Water is made of two hydrogen atoms bond to an oxygen atom. Though water
exists as separate molecules and does not form physical connections with proteins,
lipids, carbohydrates and nucleic acids, it is essential for life. The molecules that
make life possible only work if they are dissolved in water. Enzymes speed up
chemical reactions, lipids serve as energy stores and sugars are easily broken down
to make energy, but all of this is possible because these molecules are floating in a
watery environment. The hydrogen and oxygen in water are two of the big four
elements of life, but these two serve a distinct purpose as water, compared with
the purposes they serve when they are part of the carbon-containing organic
molecules.