metabolic pathways 1.6 Flashcards
metabolic pathways
integrated and controlled pathways of enzymes catalysed reactions within a cell
the 2 types of metabolic pathways
catabolic and anabolic
catabolic reactions
breakdown large molecules into smaller molecules and release energy
anabolic reactions
build up large molecules from smaller molecules and require energy
what do reversible and irreversible steps allow in metabolic pathways
allow the process to be controlled precisely
what do alternative routes in metabolic pathways allow
allow steps in the pathway to be bypassed
what controls metabolic pathways
by the presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes (controlling the activity of key enzymes)
activation energy
the energy needed to break chemical bonds in the reactants
what is the rate of chemical reactions indicated by
the amount of chemical change that occurs per unit of time
what’s the transition stage
when the reactant molecules have absorbed enough energy (normally heat energy) to make them unstable, their bonds break and the reaction can now occur
enzymes
biological catalysts which speed up the rate of reactions by lowering the activation energy
induced fit
-when the substrate binds at the active site it changes shape slightly to better fit the substrate
-this lowers the activation energy by weakening the chemical bonds of the substrate molecules
-the subsequent products of the reaction have a low affinity for the active site
affinity
chemical attraction
what type of affinity does the substrate have for the active site
a high affinity
what determines the orientation of reactants
the shape of the active site when a reaction involves two or more substrates
what happens when the substrate concentration increases
the rate of reaction also increases until all of the enzymes active sites are occupied by substrate molecules and then the rate of reaction remains at a steady rate
what effects the direction of enzyme reactions
substrate and product concentration
what happens if product concentration is too high
the enzymes can work in reverse to convert some of it back to the substrate
competitive inhibitors
-bind at the active site preventing the substrate from binding
-similar shape to substrate
-can be reversed by increasing substrate concentration so that it outnumbers the competitive inhibitors
non competitive inhibitors
-bind away from the active site but change the shape of the active site preventing the substrate from binding
-cannot be reversed by increasing substrate concentration
feedback inhibition
-occurs when the end product in the metabolic pathway reaches critical condition
-the end product the inhibits an earlier enzyme blocking the pathway, preventing further synthesis of the end product
