Biology 101 Chapter 3

The Molecules of Life


Organic compounds and organic chemistry:

Organic Compounds = any compound that contains carbon and hydrogen

Organic Chemistry = the study of organic compounds


Why carbon?

1.   4 (max) covalent bonds

2.   hydrocarbons (only contain C and H)

3.   carbon skeletons


Functional groups: main parts designated with the letter R

       Ex. Amine group of amino acids


Large molecules from small molecules:

Monomer = individual small units (like a link in a chain)

Polymer = many small units joined together in a long line (like a whole chain)

Macromolecules = very large polymers


Dehydration Synthesis: chemical process whereby monomers, smaller molecules, are linked to form polymers.  Also called addition or condensation reactions.


Hydrolysis: process whereby polymers are broken down into individual monomers.  A lytic or tear down reaction.

Most Organic Molecules are put into Four Major Classes

** (1) Carbohydrates (the sugars)



** (2) Lipids (fats, oils and waxes)



** (3) Proteins



** (4) Nucleic Acids (DNA + RNA)




The Carbohydrates

·      Ranges from simple sugars to complex carbs

     I.      The Monosaccharides:

o    Simple sugars, the monomers of carbs

o    3-7 carbon atom molecules

o    Example: Glucose

§      Simplest sugar

§      Most important to us

§      C6H12O6

o    Another ex: Fructose

o    End in “ose”

Function: fuel for cells



 II.      The Disaccharides:

o    2 simple sugars joined together

o    Ex: Sucrose, Lactose, and Maltose

Function: fuel for cells


III.      The Polysaccharides:

o    Very, very large + complex, polymers

o    Multiple units (5 – several thousand)

o    Maybe branched

o    Ex: Starch, Cellulose, Glycogen

Functions: food storage; structural




·      Widely diverse group

·      Hydrocarbon rings or chains

·      Nonpolar, hydrophobic (water-fearing)

·      Types:

1)  Fatty acids

2) Neutral fats

3) Phospholipids

4) Sterols

5) Waxes


     I.      Fatty Acids:

·      A hydrocarbon chain with a carboxyl group end

·      Very long (15-30 carbon atoms)


 II.      Neutral Fats: (fats and oils)

·      Consist of 1, 2 or 3 fatty acid molecules attached to a glycerol molecule base

·      Includes the Triglycerides

·      Structure:


III.      Phospholipids:

·      Structural lipids

·      Main component of cell membranes

·      Similar to fats but contain phosphorus

·      Structure:


IV.      Sterols:

·      Carbon skeleton of 4 fused rings

·      Regulate cellular and body functions

·      Ex: cholesterol and hormones

·      Structure:


V.      Waxes:

·      Fatty acid linked to an alcohol

·      Extremely hydrophobic


Special Terms:

Saturated = animal fats, solid at room temp., unhealthy


Unsaturated = vegetable fats + oils, liquid, “healthy”


·      Large polymers, true macromolecules

·      Millions of kinds, largest group of organics

·      Includes the enzymes

·      All proteins are encoded by DNA (proteins are the only thing coded for by DNA)

·      Made up of smaller monomers called Amino Acids

·      Only 20 different amino acids (a.a.) make up protein

·      Sequence of a.a. determines structure of protein

·      Protein structure determines function of protein

·      Peptide bonds and polypeptides

·      4 levels of protein structure:

1)  Primary: sequence of a.a.




2) Secondary: initial coiling/folding of chain




3) Tertiary: subsequent coiling, overall 3D shape




4) Quaternary: interaction among several proteins and minerals in a larger complex.  Ex. Hemoglobin


The Nucleic Acids

·      Polymers, macromolecules

·      Serve as “blueprints” for life, genetic code

·      Monomers called nucleotides

·      2 types of nucleic acid

1.  DNA = deoxyribonucleic acid

2.  RNA = ribonucleic acid


Nucleotide Structure: 3 parts

1)  Five carbon sugar ribose

2) Phosphate group

3) Nitrogenous base


Nucleic Acid Structure:

·      Sugar phosphate backbone

·      Helical shape

·      Double stranded

·      Bases face toward center, bases of opposite strands (if present) hydrogen bond together

·      Four bases make up code (A, T, C and G)

·      DNA structure and the base pairing rule


Characteristics of DNA vs. RNA

              DNA                                        RNA

Sugar deoxyribose                   sugar ribose

Double stranded                      single stranded

Four bases                               uracil in place of thymine