Amino Acids Structure

Join now

If you're ready to pass your A-Level Biology exams, become a member now to get complete access to our entire library of revision materials.

Join over 22,000 learners who have passed their exams thanks to us!

Sign up below to get instant access!

Join now →

Or try a sample...

Not ready to purchase the revision kit yet? No problem. If you want to see what we offer before purchasing, we have a free membership with sample revision materials.

Signup as a free member below and you'll be brought back to this page to try the sample materials before you buy.

Download the samples →
  • The structure of living organisms is made up of gradual levels. These levels begin with the systems, then the organs, tissues, cells and finally the organelles. If we follow up this structural sequence, we will find that the cells of any living organism are made up of organic and inorganic molecules, and each of these molecules is made up of atoms.
  • Inorganic molecules in living organisms, such as water and salts, often do not contain carbon atoms. Organic molecules, such as carbohydrates, lipids, proteins, and nucleic acids, are large molecules containing carbon and hydrogen and are known as biological macromolecules.
  • Biological macromolecules are large-sized organic compounds made up of smaller molecules. All these compounds contain the carbon element and they are vital for the life of living organisms.
  • Most biological macromolecules are called ‘polymers’. Polymers are made up of a combination of smaller molecules, called monomers, through a process called polymerization.
  • Proteins are biological macromolecules made up of smaller molecules called amino acids. The amino acids are the monomers of the protein polymers. Chemically, each amino acid is composed of four groups attached to a carbon atom. The first group is a basic group called amino group NH2. The second group is an acidic group called carboxylic group COOH. These two groups are the functional groups in the amino acid. The third group is a hydrogen atom, and the last group is terminal group R, which is a chain of carbon atoms. The R group differs from one amino acid to another.proteins-amino-acids
  • All the amino acids (except for glycine) are chiral molecules. That is, they exist in two, optically active, asymmetric forms called ‘enantiomers’ that are the mirror image of each other. This property is conceptually similar to the spatial relationship of the left hand to the right hand. One enantiomer is designated D and the other, L. It is important to note that the amino acids found in proteins almost always possess only the L-configuration. This reflects the fact that the enzymes responsible for protein synthesis have evolved to utilize only the L-enantiomers. Reflecting this near universality, the prefix L is usually omitted. Some D-amino acids are found in microorganisms, particularly in the cell walls of bacteria and in several antibiotics. However, these are not synthesized in the ribosome.
  • Proteins are made up of repeated units of amino acids that link with each other by peptide bonds. You can see these bonds between the carboxyl groups of an amino acid and the amino group of another amino acid. Water is removed in this combination.
  • The combination of two amino acids is called a ‘dipeptide compound ‘. A protein chain formed of several amino acids is called a ‘polypeptide’. When protein is being formed, the amino acids do not have to be the same. This means there are many ways to form proteins, depending on the types, order and number of amino acids in the chain.
  • About 20 amino acids participate in building the proteins such as glycine, alanine and valine. Those 20 amino acids can be classified based on lots of different features. One of them is whether or not people can acquire them through the diet. Scientists recognize three types based on this feature: the non-essential, essential, and conditionally essential amino acids.
  • However, the classifications of ‘essential’ and ‘non-essential’ don’t actually reflect their importance, as all 20 of the amino acids are necessary for human health. The eight that are labeled as essential (or indispensable) can’t be produced by the body and therefore should be supplied by food. The essential amino acids are leucine, isoleucine, lysine, threonine, methionine, phenylalanine, valine, and tryptophan. The amino acid histidine is considered semi-essential, as the human body doesn’t always need dietary sources of it. Meanwhile, conditionally essential amino acids aren’t usually required in the human diet but are able to become essential under some circumstances.
  • Non-essential amino acids are produced by the human body either out of the essential amino acids or from normal protein breakdown. These include asparagine, alanine, arginine, aspartic acid, cysteine, glutamic acid, glutamine, proline, glycine, tyrosine, and serine.

Save