Protein Metabolism
Overview Of Metabolsim
Protein catabolism is the breakdown of proteins into amino acids and simple derivative compounds, for transport into the cell through the plasma membrane and ultimately for the polymerisation into newproteins via the use of ribonucleic acids (RNA) and ribosomes.
Protein anabolism is the process by which protein are formed from amino acids (aka anabolic amino acid synthesis).
Protein catabolism is the breakdown of proteins into amino acids and simple derivative compounds, for transport into the cell through the plasma membrane and ultimately for the polymerisation into newproteins via the use of ribonucleic acids (RNA) and ribosomes.
Protein anabolism is the process by which protein are formed from amino acids (aka anabolic amino acid synthesis).
Protein Anabolism
During protein metabolism, some protein is converted to glucose in a process called gluconeogenesis, the formation of glucose from non-carbohydrate sources.
The basic difference between protein and carbohydrate is that while carbohydrates are made out of simple sugars (carbon, hydrogen, and oxygen), protein is made from amino acids (carbon, hydrogen, oxygen, nitrogen, and sufur). The nitrogen is a basic component of the protein's amino acids and accounts for 13 to 20% of the total mass.
The first step in protein metabolism is to break it into its constituent amino acids. These are absorbed into the blood stream.
The second step is to break down the amino acids into their constituent parts--catabolism, if you want to get technical about it. This removes the nitrogen or amino group from the amino acids. The process is called deamination.
Deamination breaks the amino group down into ammonia and what is termed the carbon skeleton. Ammonia is converted to urea, filtered through the kidneys, and excreted in urine. The carbon skeleton--which is composed of carbon, hydrogen, and oxygen--can then by used either for protein synthesis, energy production (ATP), or converted to glucose by gluconeogenesis.
Most authorities believe that the amount of protein converted to glucose is quite small, except under conditions of intense exercise or metablic starvation. Under these conditions amino acids produce the major source of glucose for blood sugar maintenance.
During protein metabolism, some protein is converted to glucose in a process called gluconeogenesis, the formation of glucose from non-carbohydrate sources.
The basic difference between protein and carbohydrate is that while carbohydrates are made out of simple sugars (carbon, hydrogen, and oxygen), protein is made from amino acids (carbon, hydrogen, oxygen, nitrogen, and sufur). The nitrogen is a basic component of the protein's amino acids and accounts for 13 to 20% of the total mass.
The first step in protein metabolism is to break it into its constituent amino acids. These are absorbed into the blood stream.
The second step is to break down the amino acids into their constituent parts--catabolism, if you want to get technical about it. This removes the nitrogen or amino group from the amino acids. The process is called deamination.
Deamination breaks the amino group down into ammonia and what is termed the carbon skeleton. Ammonia is converted to urea, filtered through the kidneys, and excreted in urine. The carbon skeleton--which is composed of carbon, hydrogen, and oxygen--can then by used either for protein synthesis, energy production (ATP), or converted to glucose by gluconeogenesis.
Most authorities believe that the amount of protein converted to glucose is quite small, except under conditions of intense exercise or metablic starvation. Under these conditions amino acids produce the major source of glucose for blood sugar maintenance.
- Protein anabolism is a process of building up of the proteins.
- With the involvement of enzymes and Ribonucleic acid (RNA) amino acids combine with their amino group in peptide linkages and forms long chain proteins which is called protein anabolism.
- Protein anabolism is necessary for body muscle building, strength growth and recovery.
- Adenosinetriphosphate (ATP) is one of the essential conduits that help in bringing together the smaller amino acids in to proteins.
- These are assisted by growth hormones called anabolic steroids. which will act as stimulants for the growth of proteins and in turn the muscles.
- Protein anabolism is essential to reduce fat and increase the muscular strength.
Protein catabolsim
Remember that proteins are polymers. They are large and just like lipids need to be broken down into smaller pieces before being transported into the cell. A class of extracellular enzymes called proteases break down proteins into peptides (short polymers of amino acids). There are many different proteases synthesized by cells and each of them have a different specificity. The ones used in catabolism tend to be nonspecific and attack many different peptide bonds between amino acids.
The small peptides produced can then be transported into the cell where they are further degraded into amino acids. Several of the amino acids are structurally so similar to important intermediates in the TCA cycle and other major metabolic pathways that it is a simple matter to convert them into "central metabolites". In most cases this involves removal of the amino group (deamination). Below is listed some deaminations and the products produced.
Amino Acid-Reaction-Product
glutamate-oxidative deamination-2-oxoglutarate
aspartate-oxidative deamination-oxaloacetate
alanine-oxidative deamination-pyruvate
serine-deamination-pyruvate
valine-oxidative deamination-2-oxoisovalerate
leucine-oxidative deamination-2-oxoisocaproateWhereas 2-oxoglutarate, oxaloacetate and pyruvate are central metabolites and can be easily metabolized, 2-oxoisovalerate and 2-oxoisocaproate are not and must be handled by specific catabolic pathways. Eventually these pathways lead into glycolysis or the TCA cycle.
The specific catabolic products produced depend upon the amino acid and it is not useful to study all twenty pathways. The general pattern to understand is that proteins are broken into amino acids by proteases. The amino acids are attacked by various pathways that then feed into the TCA cycle to generate energy.