Biology Processes
Chemistry of Life
Goals: Describe the structure and function of the four major organic molecules, be able to identify
molecular classes based on structure, explain how molecules will be affected as they form and/or
combine with other molecules.
Carbohydrates:
Structure: Named because of the C:H:O ratio. It is 1:2:1. The H:O ratio in water is 2:1, so Carbohydrates
are named carbonated water. Note; they do not behave as such as the term “carbohydrate” only refers
to their structure.
Monosaccharides- Mono meaning “one,” Saccharide meaning “sugar.” Literally translated as
One-Sugar. A monosaccharide is a single chemical unit that is either used by itself or part of a polymer.
Polysaccharides- A Polymer composed of linked monosaccharides. Poly meaning “many,” a
polymer is large molecule composed of many chemical linked (usually through a covalent bondremember those?) monomer subunits. For example, glucose, C6H12O6 is a monosaccharide monomer.
It can be used on its own, or it can be linked together many, many times to form the polysaccharide
polymer known as starch. If you like French Fries, then you like polymerized glucose.
Functions: Carbohydrates are used as both structural components as well as for the storage and release
of energy.
Almost all plants are composed of a substance called cellulose. Cellulose is a carbohydrate that is
produced by the plant following photosynthesis. It is used to make up the stems and internal tissues of
the plant, as well as parts of the leaves. Animals also used carbohydrates for structure. The skin in
particular contains large amounts of collagen, a type of carbohydrate.
As an energy molecule, carbohydrates are used by both autotrophic (make their own energy through a
variety of chemical processes) and heterotrophic (must consume another organism for energy)
organisms. Carbohydrates are great at storing energy because of the number of bonds between C and
H. The energy release occurs during chemical processes that break the C-H bonds and reform them with
C-O and H-O. The breaking and forming of new bonds releases a tremendous amount of energy, as
evident when you burn propane, butane, methane, octane, etc. Carbohydrates and those other organic
hydrocarbons are very different in overall structure, but fairly similar in their chemical makeup, so they
respond in roughly the same way.
Lipids:
Commonly referred to as fats and oils, lipids are also important organic molecules.
Structure: Lipids contain two important parts. They are composed of a hydrophilic “head” region
consisting of a glycerol unit, and hydrophobic fatty acid “tails.” The types of bonds in the tails, as well as
the number of tails will determine the physical properties of the lipid. Mono-glycerides will have one
tail, di-glycerides will have two tails, and tri-glycerides (the ones your doctor yells at you about) have
three tails. If the fatty acid tail is fully saturated with H atoms, then it will be solid at room temperature.
If it is not fully saturated with H atoms due to a double bond between two or more C atoms, then it will
be liquid at room temperature. Think vegetable oil used for deep frying (Oreos anyone?) vs bacon
grease left on the stove overnight. In the morning, one will still be liquid, while the other is solid, or
semi solid.
Functions: Lipids are used for three major purposes. They are major structural components of most
cells as they make up the cellular membrane. Because of their structure, only a few atoms different
from gasoline-in fact people can successfully convert vegetable oil into diesel fuel- lipids contain large
amounts of energy. They are also used extensively in the endocrine system to make hormones called
steroids.
Proteins:
Often very large polymers made from linked amino acids, these molecules have major structural and
functional uses in living organisms. They are extremely important molecules.
Structure: All proteins are composed of chemical linked subunits called amino acids. An amino acid
contains the three chemical functional groups, amino group, carboxyl group, and the “R” group. While
all amino acids contain the same amino and carboxyl group, it is the “R” functional group that gives the
amino acid its identity. There are 20 amino acids, and the nearly infinite combination of those amino
acids into large proteins is what makes up the vast majority of living tissues.
Function: Proteins can be structural in the organism, especially in animals and fungi. Muscle is
especially high in protein, as are most other major organs in the body.
Proteins also form special chemicals called enzymes. These chemicals are responsible for controlling the
rate at which many different chemical reactions occur, breaking down waste products within the cell,
and fighting off cellular invaders. These are very important molecules for survival.
Nucleic Acids:
DNA and RNA, pretty much the reason for the existence of life.
Structure: Like proteins, nucleic acids are polymers. Whereas proteins are composed of linked chains of
amino acids, nucleic acids are composed of nucleotide monomers. Like amino acids, nucleic acids also
have the important subunits. All nucleotides contain a five carbon ribose sugar, a phosphate group, and
one of four functional groups (adenine, thiamine, guanine, and cytosine). If the particular nucleic acid
one is studying is DNA, then the nucleotides will be arranged in various sequences and in a double
stranded, helical (twisted) manner. If it is RNA being studied, the nucleotides will still be arranged in
various sequences, but will be single stranded and non-helical.
Function: DNA and RNA together makeup the chemical that contains all of the information that makes
an organism, and organism. The particular sequences of the A,T,C, and G nucleotides make up the
instructions for literally all of the proteins in your body, and in pretty much the body of every other
living organism. So your hair color, eye color, metabolism, ability to fight disease, ability to digest milk,
and whether or not you will get ALS (ice bucket anyone?) are all due to the particular genetic sequences
that you possess.
Chemistry:
We will play with some models of these different molecules, but as a rule, almost any time an organic
molecule is formed by polymerization, two locations on two different monomers are affected. The first
group is an H group. During polymerization, an H atom is released, leaving a free electron on one of the
C atoms of the monomer. The other location affected is an OH group at the other end of the monomer.
This group breaks away from one of the C atoms of the monomer freeing up another electron. These
free electrons allow other monomers to bind to the original monomer, and leave us with a free H, and
OH. Guess what happens? H+OH=HOH, or H-O-H, or H 2 O, more commonly known as water. So if you
aren’t really thinking a future in Organic Chemistry is for you, just remember this; Anytime two or more
organic monomers join to form a polymer, water is formed as a byproduct.
That’s it for chemistry of life notes. Seriously, save these, and take them with you to college. They will
help greatly with first year biology classes. I should know, I’ve been there and done that.