Amino AcidsMost amino acids have the following structural properties:
A carbon (the alpha carbon) bonded to four different groups:
- A hydrogen atom (H)
- A Carboxyl group (-COOH)
- An Amino group (-NH2)
- A "variable" group
Polypeptide ChainsAmino acids are joined together through dehydration synthesis to form a peptide bond. When a number of amino acids are linked together by peptide bonds, a polypeptide chain is formed. One or more polypeptide chains twisted into a 3-D shape forms a protein.
Protein StructureThere are two general classes of protein molecules: globular proteins and fibrous proteins. Globular proteins are generally compact, soluble, and spherical in shape. Fibrous proteins are typically elongated and insoluble. Globular and fibrous proteins may exhibit one or more of four types of protein structure. The four structure types are primary, secondary, tertiary, and quaternary structure. A protein's structure determines its function. For instance, structural proteins such as collagen and keratin are fibrous and stringy. Globular proteins like hemoglobin, on the other hand, are folded and compact. Hemoglobin, found in red blood cells, is an iron containing protein that binds oxygen molecules. Its compact structure is ideal for traveling through narrow blood vessels.
Protein SynthesisProteins are synthesized in the body through a process called translation. Translation occurs in the cytoplasm and involves the rendering of genetic codes that are assembled during DNA transcription into proteins. Cell structures called ribosomes help translate these genetic codes into polypeptide chains. The polypeptide chains undergo several modifications before becoming fully functioning proteins.