Proteins - are one of the most diverse and complex organic molecules. Proteins control the chemistry of the cell. Genes produce proteins. There are literally thousands of different kinds of proteins. Proteins are made from building blocks called amino acids . There are 20 different types of amino acids. Proteins vary in length from 40 to 500 amino acids long.An amino acid is composed of a central carbon. Attached the central carbon are four groups. One of the four components attached to the carbon is hydrogen. The second group attached to the carbon is a carboxyl group . It is the carboxyl group that makes the amino acid an acid.
A third group that is attached to the central carbon is an amine group . This group can ionize and is a base. The fourth group that is attached to the central carbon is a variable group (R ). There are twenty amino acids and each one has a different variable

group.
Amino acids are put together forming a polypeptide chain . Peptide bonds hold the amino acids together..These bonds are called peptide bonds. When a peptide bond is formed, a molecule of water is removed ( dehydration synthesis ). The sequencing of amino acids is known as its primary structure . The substituting of one amino acid for another can have serious consequences. For example sickle cell anemia results when one amino acid is substituted with another one. Very seldom does a polypeptide chain stay as a straight molecule. Usually it folds on itself forming a three dimensional structure. The proteins' structure is usually a key to its function. Hydrogen bonding between the hydrogen on the amine group and oxygen on the carboxyl group allows for secondary structure to exist. There are two main types of secondary structure, beta pleated sheets and alpha helices .Seldom will polypeptide chains remain folded just once. Instead, the protein folds on itself again, forming the tertiary structure of the protein. This is myoglobin, demonstrating tertiary structure.
Tertiary structure is held together by R group interactions-ionic bonding, covalent bonding, bonding, hydrogen bonding and hydrophobic interactions.
Proteins can have more than one polypeptide chain in their structure.
When they do, the protein demonstrates quaternary structure . Below is hemoglobin, which is composed of four polypeptide chains. Each chain has an iron atom on it.Functions for Proteins

Proteins are the "workers" in the cell.
-Structural Proteins (hair, horns, etc.)
-Storage Proteins (albumin, casein)
-Sensory Proteins (rhodopsin)
-Hormonal Proteins (insulin)
-Contractile Proteins (muscles)
-Antibodies
-Enzymes
-Receptor Proteins
Note- Unlike carbohydrates and lipids, the "blue prints" for proteins are coded for by genes or
DNA. Proteins are actually made on the ribosome during a process called protein synthesis.
(How original). Lipids and carbohydrate synthesis are controlled by enzymes which are proteins.In 1869, Johann Friedrich Miescher discovered DNA.
Nucleic Acids are some of the largest molecules in the cell. There are two type of nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) . Nucleic acids are involved in carrying genetic information from one cell to the next. Nucleic acids direct the production of proteins in a cell. Nucleic acids are made of monomers called nucleotides .
A nucleotide consists of a pentose sugar , a nitrogenous base and a phosphate group . The pentose sugar used in RNA is ribose , but the sugar used in DNA is deoxyribose which is missing an atom of oxygen
The phosphate group is responsible for make DNA and RNA an acid. The phosphate group is connected to carbon #5.
There are five different nitrogenous bases. Adenine, guanine, and cytosine are used by both DNA and RNA. Thymine is used by only DNA and RNA uses uracil in place of thymine. The single ring nitrogenous base is a pyrimidine and the double ring nitrogenous base is a purine . Nucleic acids are made by bonding the phosphate of one nucleotide to the sugar of the next nucleotide. Each added nucleotide bonds with carbon #3 of the last nucleotide on the chain. This results in a backbone with a repeating pattern of sugar-phosphate-sugar- phosphate.
Along this backbone are the nitrogenous base extending outward. RNA is usually single stranded but DNA is double stranded and is analogous to a ladder. The sides of the ladder are alternation sugars and phosphate groups running antiparallel. The rungs of ladder are nitrogenous bases. Adenine base pairs with thymine and cytosine base pairs with guanine.