unit 2 KA1 - metabolic pathways Flashcards
what are metabolic pathways
metabolic pathways are integrated and controlled pathways of enzyme-catalysed reactions within a cell. they can have reversible, irreversible and alternative routes. the reactions within these pathways can be anabolic or catabolic.
what are anabolic reactions
these are reactions that build up large molecules from small molecules and require energy. example includes proteins being built up from amino acids.
what are catabolic reactions
these are reactions that break down large molecules into smaller molecules and release energy. examples include the process of food digestion, where different enzymes break down food particles so they can be absorbed by the small intestine.
describe the structure of the cell membrane
bilayer of phospholipids, with protein pores, pumps and enzymes embedded in the membrane.
role of pores in the cell membrane
form channels which allow larger molecules to diffuse through the membrane (in or out) from HC to LC
role of pumps in the membrane
move molecules and ions from LC to HC. need energy.
what controls metabolic pathways
metabolic pathways are controlled by the presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes.
describe induced fit
induced fit occurs when the active site changes shape to better fit the substrate after the substrate binds
why do products detach from the enzyme? mention affinity.
the substrate molecule(s) have a high affinity for the active sit and the subsequent products have a low affinity, allowing them to leave the active site.
what is the effect of substrate and product concentration on the direction of enzyme reactions
some 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
how do competitive inhibitors work
they bind at the active site preventing the substrate from binding. they can be reversed by increasing substrate concentration
how do non-competitive inhibitors work
they bind away from the active site but conformationally change the shape of the active site preventing the substrate from binding. non-competitive inhibition cannot be reversed by increasing substrate concentration.
how does feedback inhibtion work
this occurs when the end-product in the metabolic pathway reaches a critical concentration. the end-product then inhibits an earlier enzyme, blocking the pathway, and so prevents further synthesis of the end-product.
