Biology 101 - Biochemical Basics Part 5

A specific molecule that an enzyme acts upon, usually via interactions with the enzyme's active site. For example, starch is the substrate of salivary amylase. This means that amylase, an enzyme, catalyzes a reaction involving starch as a reactant.

It is the structural component where enzyme-substrate interactions take place. In other words, the active site is the catalytic region of an enzyme. It is structured to facilitate the binding of its substrate, often through the presence of certain amino acid residues.

It posits that a substrate will fit perfectly into the active site of its corresponding enzyme, without any conformational changes taking place. In this model, the active site is the 'lock' and its complementary substrate is the 'key.'

It posits that active sites are flexible. When a substrate approaches the enzyme, the conformation of the active site will change to better fit the substrate. The induced fit model is a more recent adaptation of the lock-and-key model.

A region of an enzyme, separate from the active site, where molecules can bind and affect enzyme function. Allosteric binding can either facilitate or inhibit the binding of substrate to the active site.

It binds to an enzyme on its active site, inhibiting the reaction. Specifically, these inhibitors compete with the substrate and block it from binding the active site.

It binds to an enzyme on a region outside of its active site, inhibiting the reaction. Specifically, these inhibitors bind an allosteric site, inducing a structural change in the enzyme that decreases its efficiency. Substrates can still enter the enzyme's active site.

Disaccharides. Maltase breaks down maltose into two glucose molecules. Sucrase cleaves sucrose into glucose and fructose, and lactase breaks down lactose into glucose and galactose.

This molecule is adenosine triphosphate (ATP), the major form of cellular energy. ATP consists of three phosphate groups bound to the ribonucleoside adenosine. The cleavage of the third phosphate bond facilitates the release of energy, which the cell harnesses to drive biological processes.

Phosphoanhydride bonds. These phosphoanhydride bonds exist between phosphate groups on molecules like ATP (shown) and ADP. The name of these bonds comes from the reaction that forms them: dehydration (removal of H2O). Predictably, they can be broken by the reverse reaction, hydrolysis (addition of H2O).