Metabolic pathways are integrated and controlled pathways of enzyme-catalysed reactions within a cell.

Metabolic pathways can have reversible steps, irreversible steps and alternative routes.

Reactions within metabolic pathways can be anabolic or catabolic.

Anabolic reactions build up large molecules from small molecules and require energy.

Catabolic reactions break down large molecules into smaller molecules and release energy.

Protein pores, pumps and enzymes are embedded in membranes.

The active site of an enzyme creates an energetically favourable environment for the reaction to take place and lowers the activation energy.

Induced fit occurs when the active site changes shape to better fit the substrate after the substrate binds.

The substrate molecule(s) have a high affinity for the active site and the subsequent products have a low affinity, allowing them to leave the active site.

Metabolic pathways are controlled by the presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes.

Some metabolic reactions are reversible.

As some metabolic reactions are reversible, the presence of a substrate or the removal of a product will drive a sequence of reactions in a particular direction.

As substrate concentration is increased, the rate of enzyme reactions also increases until the enzyme concentration becomes a limiting factor.

Competitive inhibitors bind at the active site preventing the substrate from binding.

Competitive inhibition can be reversed by increasing substrate concentration.