1. Joseph A. Castellano, Ph.D.
Compounds of Life
Biological Molecules By
Joseph A. Castellano, Ph.D.
RESEED Silicon Valley
Reference: Focus on Physical Science, Glencoe/McGraw-Hill,
Columbus, Ohio, 2007, Pages This textbook is used in
many California Middle Schools.

2. Biological Molecules
Biological molecules present in all living organisms include lipids (fats and oils), proteins, nucleic acids and carbohydrates.
Proteins, nucleic acids and carbohydrates are large natural polymer molecules in all living organisms that share the same few monomers:
- Amino acids make proteins
- Nucleotides make nucleic acids (DNA)
- Sugars make complex carbohydrates

3. Nucleic Acids
A nucleic acid is a biomolecule found in all plant, animal and human cells.
RNA (ribonucleic acid) and DNA (deoxyribonucleic acid) store cellular information in all living cells in the form of a “genetic code.”
Every person’s genetic code is different. The code in your cells determine the color of your eyes and hair as well as every other feature of your body that is unique to you and only you.

4. Nucleotide Monomers
The nucleic acid DNA is composed of monomers called nucleotides.
A nucleotide is composed of a nitrogen base, a sugar and a phosphate group:
Cytosine
(a nitrogen base)
Nucleotide Monomer

5. Nucleic Acid Polymers
The nucleic acid polymer, DNA, is composed of nucleotides that have the same four nitrogen bases:
- Adenine - Guanine - Cytosine - Thymine
Scientists identify these four by the first letter of their names: A, G, C, T.
A single DNA molecule can have thousands of these nucleotides arranged in any number of sequences (ATGCTGCA, etc.); the exact sequence is the genetic code and is different for each person.

6. DNA Chemical Structure
The dotted lines show
hydrogen bonds, which
hold the two strands of
nucleic acids together
in a coil-like
arrangement
called a “double helix.”
Methane

7. DNA Molecular Model
Methane

8. Lipids
Lipids are fats and oils that contain carbon, hydrogen and oxygen atoms.
Like hydrocarbons, lipids are non-polar compounds that are not soluble in water.
Some lipids are long carbon chain, carboxylic acids often called fatty acids.
Neutral lipids in animal fats are fatty acids combined with glycerol to form compounds called fatty esters.

9. Lipids – Fats and Oils
Fatty acid lipids can be saturated molecules with only single bonds between carbon atoms. Bacon contains the solid saturated fatty acid, stearic acid.
Fatty acids with one or more double bonds between carbons are called unsaturated and are usually liquid. Olive oil contains the unsaturated lipid, oleic acid.

10. Carbohydrates
A carbohydrate is an organic compound that contains the elements carbon, hydrogen, and oxygen. Carbo- stands for carbon and hydrate for water.
Simple Carbohydrates are sugars. There are many different kinds of sugars. Some can bought in boxes from the grocery store, but many are also present naturally in foods such as fruits and milk.
Carbohydrates are used by cells to store and release energy.

11. Simple Carbohydrates
The simplest carbohydrate is glucose. The molecular formula is:
C6H12O6
The structural formula for glucose shows how the atoms are arranged.
Carbohydrates with only one carbon
ring are called monosaccharides

12. Complex Carbohydrates
A complex carbohydrate is a long chain polymer made up of simple carbohydrate monomers.
Starch, cellulose and glycogen are all built from glucose monomers, but the monomers are arranged differently in each case.
Starch and cellulose are found in plants, while glycogen is present in liver and muscle cells.
Complex carbohydrates have many carbon rings,
so they are called polysaccharides.

13. Polymers from Glucose Cellulose Glycogen Glucose Plants, Trees,
Fruits, Vegetables
Straight Polymer Chain Backbone
Glucose
Cellulose
Animal & Human
Liver & Muscles
Branched Polymer Chain Backbone
Glycogen

14. Proteins
Proteins are long chain polymer molecules formed by connecting amino acids together.
Glycine is the simplest of the 20 common amino acids that occur in nature.

15. Proteins
Proteins are made in human cells by a complex process involving DNA.
The DNA directs the amino acids to combine with each other in a very specific sequence to produce the desired protein for each organ.
For example, the protein collagen makes up skin while hemoglobin is the protein in blood that carries oxygen to our cells.
Other proteins contract muscle tissue and fight viruses and bacteria that invade us.

16. Protein Structure
Proteins in nature have a helical structure, like a coil.
The dashed lines in this protein molecular model represent “hydrogen bonds” that hold the atoms in the coil-like structure.

17. Summary
All living organisms are composed of biological molecules that contain carbon, hydrogen, oxygen, nitrogen and sometimes sulfur and phosphorous.
Nucleic acids, proteins, lipids and carbohydrates are the main compounds of life.
Biological molecules are formed from amino acids, sugars, long chain “fatty acids” and nucleotides.
Research on biological molecules leads to an understanding of the causes and cure of human diseases.

18. This presentation was produced as a public service to help middle school and high school science teachers develop experiments, presentations and demonstrations that can be used in their classes.
More science experiments and demonstrations are available on the RESEED Silicon Valley web site:
RESEED (Retirees Enhancing Science Education through Experiments and Demonstrations) is a program aimed at stimulating greater interest in science by middle school students.