Metabolism and Enzymes

You open the laboratory door, enter hurriedly, and sit next to your lab partner, James. You are already 5 minutes late and Prof. Wilson has started the class. James whispers that Prof. Wilson is revising some of the concepts you learnt in the lecture this week before going into the specifics of the lab practical. 

Prof. Wilson: Remember, metabolism is the totality of chemical reactions that occur within the cells of living organisms to sustain life. It will provide our cells with energy to perform our daily tasks. Our body is so efficient and so complex at the same time (he says pointing to the poster on the wall)!

Website: Metabolism diagram

Prof. Wilson continues.

Prof. Wilson: As part of a metabolic pathway, a starting molecule undergoes some changes in a series of metabolic reactions, to end up producing a different molecule at the end of the reaction.

You: This sounds so time-consuming, Prof. How is our body so efficient as you mentioned earlier? Is there something that can speed up these reactions?

Prof. Wilson: Yes, enzymes! An enzyme is made up of protein macromolecules, which increase the rate (speed) of metabolic reactions without itself being changed in the process! It’s like a “helping hand” to the process. Each step is catalyzed by a specific enzyme. Enzymes are specific as they have unique three-dimensional structures for each reaction. They even take a similar name as the starting molecule (reactant) they bind to, such as lactase enzyme for lactose as a reactant. Remember, enzymes can catalyze both anabolic and catabolic reactions. 

[Anabolic pathways use up energy to build complex larger molecules from simpler smaller molecules. 

Catabolic pathways lead to release of energy from breaking down complex large molecules into simple smaller molecules.]