Response to Dr Kesel's letter to the editor:

The status of a reversible reaction is conveniently assessed by evaluating its reaction quotient (Q). For a reversible reaction described by m A + n B ⇌ x C + y D, the reaction quotient is derived directly from the stoichiometry of the balanced equation as

Biochemical reactions are occurring constantly in cells, converting starting substances to different products, usually with the help of enzymes that speed the reactions. Without enzymes, it would take far too long for most reactions to occur to be useful to the cell!

Overview

Overview

Nearly all the energy used by cells comes from the bonds that make up complex organic compounds. These organic compounds are broken down into simpler molecules, such as glucose. As a result, cells extract energy from glucose over many chemical reactions—a process called cellular respiration.
Cellular respiration can occur aerobically (with oxygen) or anaerobically (without oxygen). In the presence of oxygen, cellular respiration starts with glycolysis and continues with pyruvate oxidation, the...

In most cases, excessive hormone production is prevented by negative feedback—a loop that starts with a stimulus inducing the release of a particular substance, like a hormone, to maintain a certain level before triggering a signal that results in a decrease in further release of the hormone.