Subsequent amino acids will be added onto the carboxylic acid terminal of the growing protein. Within protein structures, this amide linkage is known as the peptide bond. The primary sequence of a protein is linked together using dehydration synthesis that combine the carboxylic acid of the upstream amino acid with the amine functional group of the downstream amino acid to form an amide linkage. This specific ordering of amino acids is known as the protein’s primary sequence. Thus, as the amino acids are linked together to form a specific protein, they are placed within a very specific order that is dictated by the genetic information contained within the RNA. Within cellular systems, proteins are linked together by a complex system of RNA and proteins called the ribosome. The basic structure of an amino acid is shown below:įigure 11.2 General Structure of an Alpha Amino Acid They differ from one another only at the R-group postion. Within living organisms there are 20 amino acids used as protein building blocks.
In the diagram below, this group is designated as an R-group. In addition to the amine and the carboxylic acid, the alpha carbon is also attached to a hydrogen and one additional group that can vary in size and length. The alpha designation is used to indicate that these two functional groups are separated from one another by one carbon group. As their name implies they contain a carboxylic acid functional group and an amine functional group. The major building block of proteins are called alpha amino acids. You will find that the major macromolecules are held together by the same chemical linkages that you’ve been exploring in Chapters 9 and 10, and rely heavily on dehydration synthesis for their formation, and hydrolysis for their breakdown.įigure 11.1: The Molecular building blocks of life are made from organic compounds.įun Video Tutorial Introducing the Major Macromoleculesīiological Molecules – You Are What You Eat: Crash Course Biology #3.ġ1.2 Protein Structure and Function Amino Acids and Primary Protein Structure This chapter will focus on an introduction to the structure and function of these macromolecules. Recall that the monomer units for building the nucleic acids, DNA and RNA, are the nucleotide bases, whereas the monomers for proteins are amino acids, for carbohydrates are sugar residues, and for lipids are fatty acids or acetyl groups. In Chapter 6, you were introduced to the polymers of life and their building block structures, as shown below in Figure 11.1. All of the major macromolecule classes are similar, in that, they are large polymers that are assembled from small repeating monomer subunits. These are the carbohydrates, lipids (or fats), proteins, and nucleic acids. Within all lifeforms on Earth, from the tiniest bacterium to the giant sperm whale, there are four major classes of organic macromolecules that are always found and are essential to life. 11.1 Introduction: The Four Major Macromolecules
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