Building Blocks of Proteins
Proteins play a vital role in our human body structure and are found in every organism in this
ecosystem. Amino acid are the “building blocks of protein “. Proteins control most of the metabolic, sensory, reproductive and biosynthetic
activities within the cell. Protein is made from one or two polypeptide chains and each chain is
built from small molecules of amino acids. Proteins play a vital role in storage, movement,
and support for cells for cells in human body. It also helps in digestion of food. Enzymes are
proteins which help in digestion by increasing speed of chemical reactions in our body.
These are called digestive enzymes.
BASIC BUILDING BLOCKS OF PROTEINS
The basic building blocks of proteins is amino acids. The food we eat contain protein having 20 amino acids link together within our body to form large molecules of protein. Amino acids possess a great diversity of nature in proteins. They contain carboxyl, an amine group, along with side chain to each amino acid. Amino acids have carbon atom attach to lysine and carbon atoms are ordered are alpha, beta, gamma. They are made up of carbon, hydrogen, oxygen, nitrogen, and sulfur. Thus, these are required for protein formation in the body.
AMINO ACIDS: BUILDING BLOCK
The basic structure of amino acid follows a similar pattern. They contain carbon atom in the center surrounded by three chemical groups. One carboxyl groups and second amine group and third is R-group which can be a single hydrogen atom. Amino acids, especially glutamic acid which act as a flavor enhancer. In stomach proteins are broken down into amino acids then are digested. Hence, amino acids are the substances which are never excreted out through urine under normal circumstances in any healthy individual. 1.0 gram of protein may yield 5.65 kcal energy.
DISCOVERY OF AMINO ACIDS
The two scientists Harold Urey and John Haldane were both responsible for the discovery of amino acids. Scientist Stanley Miller
analyzed the compound settled during the said experiment and he discovers that organic compound mainly amino acid. Glycine, Glutamic acid, Aspartic acid, Alanic are the
amino acids discovered by Stanley Miller.
AMINO ACIDS FUNCTIONS
They play a vital role in growth and development or repair of the body. All enzymes are proteins except ribozymes. They are the building blocks of the body. Proteins are the polymer of amino acids. The main source of proteins is fish, egg, milk etc. Amino acids for growth and repair of the body. Acts as enzymes or biological catalyst in metabolic reactions. Antibodies are proteins, which works for the defense of the body. Collagen protein is present in bones, tendons, cartilage and transports fatty acids and lipids in the blood. Haemoglobin, visual pigments, cytochromes are proteins. The proteins have a significant role in the structural and functional organization of the cell. The structural proteins constitute many cellular components and extracellular parts like cuticle, fibers, sensory, reproductive and biosynthetic activities within the cell.
GETTING AMINO ACIDS FROM YOUR DIET
Our body can manufacture 11 amino acids on its own if necessary. The remaining 9 amino acids are only available in your diet.
Proteins from animal source give you essential amino acids and also from plants sources. You can get the protein your diet regularly. Protein-rich foods
are Egg, Fish, Meat, Salmon, Milk etc. They contain all essential amino acids which are good for your health.
Polypeptides are the simplest form of protein. Long, linear chains are bond together by amino acid
which is 2000 amino acids long. Order of chain determines the structure and shape of a polypeptide
chain. When amino acids are bonded together by peptide bond they create polypeptide backbone
extending out from one of the amino acids. A ribosome is a site where protein synthesis occurs.
The information for the sequence of amino acids is present in the sequence of nitrogenous bases
of mRNA. The initiation of the polypeptide chain in prokaryotes is always brought out by the amino
acid. Methionine which is regularly coded by codon AUG but rarely also by GUG (for valine) as also
PROCESS OF PROTEIN SYNTHESIS
Central Dogma – The process of synthesis of proteins involves one of the central dogma of the molecular biology. This path for the flow of genetic information has been termed by crick (1956) as the central dogma. According to this, genetic information flows from nucleic acid to protein. We know that DNA is stably inherited fro, parents to offsprings. According to central dogma, the flow of information takes place from DNA to RNA and from RNA to proteins.
The synthesis of DNA on RNA template in RNA tumor viruses was demonstrated by two American Scientists, H.Temin, and D.Baltimore. The discovery was considered significant for understanding cancer. The above discovery introduced the concept of central dogma in reverse. According to this information, flow is not necessarily from DNA to RNA but maybe from RNA to DNA also.
TYPES OF PROTEINS
1. Histones – These are basic proteins of unique importance in the packaging of eukaryotic DNA. They have low molecular
weight and a high portion of positively charged amino acids which help to bind the proteins.
The positively charged R-groups of histone amino acids bind strongly to the negatively charged phosphate groups of
DNA. This binding result help in the formation of a helical form of DNA molecule so that length of the molecule is reduced considerably without
2. Non-Histone Proteins – These are high molecular weight acid or neutral proteins associated with the
nucleoprotein fibers. There is three major type of histone proteins – 1. Structural proteins which provide
the axis or scaffold of the chromosome. 2. Enzymatic proteins which act as an enzyme and help
in replication of DNA and transcription process. 3. Regulatory proteins which regulate the gene action.