Video Transcript
What is a defining feature of an
organic molecule found in a living organism? (A) It does not contain hydrogen
atoms. (B) It contains carbon and hydrogen
linked together. (C) It contains hydrogen bonds. Or (D) it cannot be broken down
into smaller subunits.
This question asks us about organic
molecules, which include biological macromolecules. The prefix macro- means large, so
these are large molecules made up of smaller subunits.
There are four groups of biological
macromolecule: nucleic acids, proteins, lipids, and carbohydrates. They are all very important
molecules in the cell. For instance, you may have learned
that DNA, a nucleic acid, contains the genetic code that has all of the instructions
for protein production. Proteins, on the other hand, are
especially important for enzymatic processes, fighting infection, and providing
structure. Carbohydrates are important sources
of energy. Glucose is the primary substrate in
cellular respiration, and glycogen is the glucose storage molecule of animals.
Nucleic acids, proteins, and
polysaccharides, complex carbohydrates, are called polymers since they are made up
of single, repeating monomer subunits. Poly- means many, mono- means one,
and “mer” means unit.
Lipids are not made up of repeating
units, so they are not regarded as polymers, but they are still macromolecules. While all of these molecules have
different functions, they all share something in common. They are considered organic because
they possess atoms of carbon that are bonded to atoms of hydrogen. This is true for all organic
molecules.
On the other hand, there are some
compounds in cells that are considered inorganic. What does this mean? Here, the prefix in- means not, so
these molecules are not organic and do not contain carbon–hydrogen bonds. Examples of inorganic molecules
include water and oxygen gas.
Now that we have reviewed the
difference between organic and inorganic molecules in cells, we can return to our
question. We now know that the correct answer
is (B). The defining feature of an organic
molecule found in a living organism is that it contains carbon and hydrogen linked
together.
