Video Transcript
The diagram provided shows the conversion of amino acids into a polypeptide chain and the breakdown of a polypeptide chain into amino acids. Which of the following options correctly describes the nature of these two reactions? Option (A) reaction X is a catabolic reaction, and reaction Y is an anabolic reaction. Or option (B) reaction X is an anabolic reaction, and reaction Y is a catabolic reaction.
To answer this question, let’s first understand what some of the key terms mean. The question is asking us to identify which of reactions X and Y is anabolic and which is catabolic. Anabolic reactions are metabolic reactions that synthesize large molecules from smaller ones. One example is the formation of proteins. This occurs by the joining of many small molecular subunits called amino acids. Bonds called peptide bonds form between separate amino acids, joining them together to form a polypeptide chain. This reaction is anabolic because a large molecule is made from smaller ones.
In contrast, catabolic reactions are metabolic reactions that break down large molecules into smaller components. In our example, the peptide bonds between amino acids will break separating them, leaving us with many individual amino acids. This is an example of a catabolic reaction because a large molecule has been broken down into smaller components. Let’s bring back the definition of anabolic reactions and have another look at our question.
Our question is asking us to identify out of reactions X and Y which is anabolic and which is catabolic. Reaction X shows single amino acids joining to form a polypeptide chain, while reaction Y shows the bonds between individual amino acids breaking, therefore breaking down the polypeptide chain into its amino acid components. Reaction X shows a large molecule being synthesized from smaller ones and is therefore an example of an anabolic reaction. Reaction Y shows the breakdown of a large molecule into smaller components and is therefore an example of a catabolic reaction.
We now have enough information to answer our question. Option (B) describes reaction X as an anabolic reaction and reaction Y as a catabolic reaction and is therefore our correct answer.
