Overview of the Organic Molecules
Cells contain a few types of small organic molecules. All organic molecules are made from Carbon, Hydrogen, and
Oxygen. Nitrogen, Phosphorus, and Sulfur are found in some. Some examples may be familiar to you.
1. Sugars – simple sugars are sweet. EX: glucose, fructose, galactose, ribose, deoxyribose
2. Amino Acids – there are 20 different types including Tryptophan, Lysine, Phenylalanine. All include Nitrogen in
their structure. A few have Sulfur.
3. Fatty Acids – there are a variety of these. May be classified as ‘saturated’ or ‘un-saturated’ on food labels.
4. Sterols – These are the building blocks of steroid hormones.
5. Nucleotides – You won’t recognize any of them. All include Nitrogen and Phosporus in their structure.
These molecules are small enough so that they can be moved in and out of the cell.
Cells can carry out chemical reactions in which the small molecules listed above are joined together in specific ways to
make larger molecules. These molecules form 4 major categories.
1. Carbohydrates are made from sugars. There are 3 categories depending upon the size:
a. MonoSaccharide = 1 sugar
EX: Glucose is the fuel for the cell. Produced by plants during Photosynthesis.
b. DiSaccharide = 2 sugars linked together
Disaccharides are sweet.
EX: sucrose=glucose+fructose. Sucrose is transported throughout body of the plant
c. PolySaccharide = 100s or 1000s of sugars linked into chains or branched chains
Polysaccharides are not sweet.
EX: starch (plant energy storage molecule), cellulose (plant cell wall), Glycogen (animal energy storage)
2. Proteins (aka Polypeptides) are made from 2 or more (usually 100s) amino acids linked into straight chains.
Functions are quite varied. This is the class of molecules that does most of the cell’s work and forms much of its
structure. There are 1000s of different types of proteins. Each has a specific job. Their activities include:
a. form fibers such as in tendons, or hair that are outside the cell
b. move materials around inside cell (motors)
c. move materials across cell membranes (pumps)
d. form fibers inside cells (cell skeleton)
e. carry out chemical reactions (Enzymes). Each enzyme can only make one specific chemical reaction take
place so there are thousands of different enzymes in every cell at any point in time.
3. Lipids include all the molecules that will not dissolve in water. They are made from a variety of small molecules
including Fatty Acids and Sterol. There are 4 categories.
a. Fats/Oils = Glycerol + 3 fatty acids. Glycerol is a sugar
Store energy. Insulation against cold.
b. Phospholipids = Glycerol + 2 Fatty Acids + Phosphate
One of the major molecules in a cell’s plasma membrane. EX: Lecithin
c. Steroids = Sterol modified in slight ways to make different molecules.
Includes cholesterol and the steroid hormones such as estrogen & testosterone
d. Waxes - Waterproof surfaces
4. Nucleic Acids are made from Nucleotides. There are 2 major types: DNA and RNA.
DNA is the genetic material. The DNA controls how a cell makes proteins. Chromosomes are structures, made
from DNA and proteins, which form in cells when they reproduce.
RNA molecules play various roles in the synthesis of protein by the cell.
Molecules such as polysaccharides, proteins, and nucleic acids which are made by linking many small molecules of the
same type together into chains are called Polymers. The small molecules used to make a polymer are referred to as
Monomers. Since these polymers are often very large, they are commonly referred to as Macromolecules.
Cells are constantly linking together monomers to make (=synthesis) macromolecules. Cells are also constantly breaking
apart the macromolecules into their monomers (= digestion). Both processes, macromolecular synthesis and digestion,
require specific Enzymes. If the enzymes are not present, the reactions will not occur.
Polymer
SYNTHESIS
Monomer
DIGESTION
Summary of the Macromolecules
Polymer
SYNTHESIS
DIGESTION
Monomer
---------------------------------------------------------------------------------------------------------------------------Polysaccharides
Monosaccharide
Disaccharide
Polysaccharide
SYNTHESIS
DIGESTION
---------------------------------------------------------------------------------------------------------------------------Proteins = Polypeptide
Amino Acids
DiPeptide
Protein=Polypeptide
SYNTHESIS
DIGESTION
---------------------------------------------------------------------------------------------------------------------------Nucleic Acids
Nucleic Acid
SYNTHESIS
DIGESTION
Nucleotide
---------------------------------------------------------------------------------------------------------------------------Lipids
Fats and Oils (aka Triglycerides)
Steroid
Fatty Acid
Fatty Acid
Fatty Acid
Fatty Acid
Fatty Acid
Fatty Acid
Glycerol
Glycerol