Yeast, a cellular model. Yeast is a simple living being that functions in practically the same way as human cells. It is an historical subject of fundamental research to understand cellular and genetic phenomena. It is a representative model of all eukaryotic cells.
Covenant. An agreement, contract, or written promise between two individuals that frequently constitutes a pledge to do or refrain from doing something. The individual making the promise or agreement is known as the covenantor, and the individual to whom such promise is made is called the covenantee.
An obligation is a legal relationship whereby a person, called the obligor, is bound to render a performance in favor of another, called the obligee. Performance may consist of giving, doing, or not doing something. In a contractual sense, an obligor is the debtor.