The text discusses three forms of enzyme inhibition: uncompetitive inhibition, competitive inhibition, and irreversible inhibition.(a) Describe how an enzyme inhibitor of each type works.(b) What kinds of bonds are formed between an enzymeand each of these three kinds of inhibitors?
Electron Transport Chain
The electron transport chain, also known as the electron transport system, is a group of proteins that transfer electrons through a membrane within mitochondria to create a gradient of protons that drives adenosine triphosphate (ATP)synthesis. The cell uses ATP as an energy source for metabolic processes and cellular functions. ETC involves series of reactions that convert redox energy from NADH (nicotinamide adenine dinucleotide (NAD) + hydrogen (H)) and FADH2(flavin adenine dinucleotide (FAD)) oxidation into proton-motive force(PMF), which is then used to synthesize ATP through conformational changes in the ATP synthase complex, a process known as oxidative phosphorylation.
Metabolism
Picture a campfire. It keeps the body warm on a cold night and provides light. To ensure that the fire keeps burning, fuel needs to be added(pieces of wood in this case). When a small piece is added, the fire burns bright for a bit and then dies down unless more wood is added. But, if too many pieces are placed at a time, the fire escalates and burns for a longer time, without actually burning away all the pieces that have been added. Many of them, especially the larger chunks or damp pieces, remain unburnt.
Cellular Respiration
Cellular respiration is the cellular process involved in the generation of adenosine triphosphate (ATP) molecules from the organic nutritional source obtained from the diet. It is a universal process observed in all types of life forms. The glucose (chemical formula C6H12O6) molecules are the preferred raw material for cell respiration as it possesses a simple structure and is highly efficient in nature.
The text discusses three forms of enzyme inhibition: uncompetitive inhibition, competitive inhibition, and irreversible inhibition.
(a) Describe how an enzyme inhibitor of each type works.
(b) What kinds of bonds are formed between an enzyme
and each of these three kinds of inhibitors?
Enzyme
- Coined by Kuhne in 1878.
- Popularly known as biological catalysts.
- Metabolic and cellular reactions are largely enzymatically catalyzed which otherwise will complete in many years if they are not catalyzed by enzymes.
- For example, The digestion of a single food meal in the stomach will occur in years if not enzymatically catalyzed.
- The rate of enzyme-catalyzed reaction or the rate at which product is formed is studied under enzyme kinetics
Inhibition
- It is the process in which enzyme activity is adversely affected, either partially or completely in the presence of a molecule known as an inhibitor.
- The rate of the formation of products is affected by the combination of an inhibitor to the enzyme.
- The inhibitor may or may not bind to the enzyme's active site.
- The inhibitor may or may not resemble the substrate structurally.
- Inhibition is of two types: Reversible and irreversible inhibition.
Competitive Inhibition
- It is a type of reversible inhibition
- Here, the inhibitor resembles the substrate.
- The inhibitor competes with the substrate for binding at the active site of an enzyme.
- The strength of inhibition depends upon the concentrations of substrate and inhibitors.
- By increasing the concentration of substrate, inhibition can be reversed. In this case, Vmax remains the same but Km will increase as compared to a normal enzyme-substrate association.
Uncompetitive Inhibition
- It is also a reversible inhibition.
- Here, the inhibitor binds to an allosteric site of an enzyme.
- In this case, binding occurs with the Enzyme-substrate complex only not the free enzyme.
- In this case, Vmax and Km decrease in the presence of inhibitors.
Irreversible Inhibition
- It is a type of inhibition that can't be reversed or there is a slow dissociation of the inhibitor from the enzyme.
- There is a tight association of inhibitors at the enzyme's active site.
- An enzyme is almost inactive in the presence of inhibitors.
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