Polysaccharide
Generally in an enzyme-catalyzed reaction, the reactant is called the substrate, which in association with the enzyme forms the product.
the cell membrane
the cell membrane
The first reaction of glycolysis, where glucose is phosphorylated (a phosphate group is added) to give glucose - 6 - phosphate requires ATP. This reaction is catalyzed by the enzyme hexokinase
Lactose intolerance is the inability to efficiently convert lactose into glucose and galactose, a reaction catalyzed by the enzyme lactase. (A rule of thumb for enzyme nomenclature is that many enzyme names typically take most of the name of their substrate and slap an "-ase" at the end.)
Substrates
In a chemical reaction, the starting materials are called the reactants.
The chemicals at the start of a reaction are always called the reactants.The chemicals at the end of a reaction are always called the products.
The reactants.
Irreversible :D
Reactants are the starting components in a chemical reaction. Since you did not mention what chemical reaction you are referring to, there can be no further detail on the question.
a reversible reaction