Metabolic Pathways Flashcards
What forms a metabolic pathway?
In many reactions, one chemical is changed to another, then to another via a series of enzyme controlled steps
What does anabolic pathways do?
Synthesise larger molecules from smaller ones and require energy
What does catabolic pathways do?
Break larger molecules down to smaller ones and release energy
What steps can catabolic and anabolic pathways have?
Reversible and Irreversible
Metabolic pathways can also contain what?
Alternative routes usually occurring when there is plentiful supply of one metabolite in a pathway
Each step in a metabolic pathway is driven by what?
A particular enzyme and a particular gene that codes for each enzyme, so as long as the enzymes proteins are correctly functioning, the pathway proceeds
Enzyme action is controlled by what?
By the presence or absence of particular enzymes and regulated by the rate of reaction of key enzymes
What do enzymes have (in terms of active site)?
The enzymes active sites have a high affinity for substance molecules, and when the two combine, the reactants are orientated to the active site, the activation energy is lowered and the products, which have a lower affinity for the active site, are then released.
The active site is not a rigid structure as when the substance enters the active site, it changes slightly making it fit and substrate molecule snugly - known as induced fit
What is the effect of substrate concentration?
At low concentrations of a substrate, reaction rate is low due to too few substrate molecules to make full use of all active sites
Increase in substrate results in an increase in reaction rate as more of the active site are in use
Eventually a further increase in substrate concentration will have no more effect on reaction rate as all the active sites are in use
As some reactions are reversible the presence of substrate or product can drive the direction of the reaction
What do inhibitors do?
Control metabolic pathways by decreasing the rate of enzyme action
What do competitive inhibitors do?
Bind to the active site preventing the substrate binding but can be overcome by increasing the substrate concentration as there are then higher chance of enzyme-substrate interaction
What do non-competitive inhibitors do?
They become attached to a non-active site causing a change in shape of active site and cannot ne reversed by increasing substrate concentration
What do feedback inhibitors do?
Happens as the concentration of end product binds up and reaches critical concentration, it inhibits an earlier enzyme, blocking the pathway and so prevents further synthesis of the end product
