Key area 6- Metabolic Pathways Flashcards
What is a metabolic pathway?
.They are integrated and controlled pathways of enzyme-catalysed reactions within a cell
.They can have reversible steps, irreversible steps, and alternative routes
.They can be anabolic or catabolic
What is an anabolic reaction?
.They build up large molecules from small molecules
.It requires energy
.For example, the synthesis of polypeptides from amino acids
What is a catabolic reaction?
.They break down large molecules into smaller molecules
.This releases energy
.For example, in glycolysis
, glucose is broken down to pyruvate
What are metabolic pathways controlled by?
.They are controlled by the presence or absence of particular enzymes and the regulation of the rate of reaction by key enzymes
.Most metabolic reactions are reversible and the presence of a substrate or the removal of a product will drive a sequence of reactions in a particular direction
What is the activation energy?
.It is the energy needed to break chemical bonds in the reactant chemicals
What are the stages of the induced fit of the active site on the enzyme?
.The active site of an enzyme is not a rigid structure. It is flexible and dynamic
.When a molecule of a substrate enters the active site, the shape of the active site changes slightly to better fit the substrate after the substrate binds- this is called induced fit
.Induced fit ensures that the active site comes into very close contact with the molecules of substrate and increases the chance of the reaction taking place therefore making the reaction take place more easily
.The substrate molecules have a high affinity for the active site and the subsequent products have a low affinity allowing them to leave the active site
.After the reaction is over, the product is released and the active site returns to its normal shape and the enzyme is free to attach to more substrate molecules
Why does an enzyme only bind to one substrate?
.Because the enzyme’s active site is specific to a substrate
.They show a high affinity for each other
What does an enzyme require to function efficiently?
.Temperature
.pH
.Substrate concentration/correct substrate
.Enzyme concentration
.Product concentration
.Presence of inhibitor
What is the relationship between enzymes and substrate concentration?
.As substrate concentration increases, rate of reaction increases and then the rate of reaction remains constant as the active sites are all occupied because the enzyme concentration is the limiting factor
What is an inhibitor?
.A substance that decreases the rate of an enzyme controlled reaction
What is a competitive inhibitor?
.It has a similar molecular structure to the substrate
.It competes with the substrate for the active sites on the enzyme
.It binds to the active sites therefore preventing the substrate from binding so the rate of reaction decreases
.This competitive inhibition can be reversed by increasing the substrate concentration
What is a non-competitive inhibitor?
.It binds away from the active site but changes the shape of the active site therefore preventing the substrate from binding
.This non-competitive inhibition cannot be reversed by increasing the substrate concentration
What is feedback inhibition?
.It occurs when the end-product in a metabolic pathway reaches a critical concentration
.This end-product inhibits an earlier enzyme, blocking the pathway, and so prevents further synthesis of the end-product
