All metabolic reactions in a cell are catalyzed by which of the following?

Enzymes are a type of protein. They catalyze (cause or accelerate) different reactions and processes. Almost all cellular function is catalyzed by some type of enzyme.
Amino acids are what make up proteins. Proteins are polymers of 20 amino acids.
Phospholipids are a type of lipid. They consist of two fatty acids bonded to a phosphate group. The phosphate group is polar and soluble in water whereas the hydrocarbon tail of the fatty acids is nonpolar and non-soluble in water. This quality is important in the function of cellular membranes, including the plasma membrane, as the molecules organize themselves in a way that creates a barrier to protect the cell.
Steroids are a type of lipid. They are a component of membranes and an essential part of many hormones and drugs.