Phosphofructokinase (PFK) is an important enzyme in virtually all living cells. It performs the committed step in the glycolytic pathway, namely, the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate. Glycolysis is a pathway that uses glucose to maintain a steady amount of ATP, the major energy carrier in living cells. Phosphofructokinase is a multisubunit protein. In such proteins, the subunits may behave cooperatively; that is, the activity of one subunit influences the activity of all the other subunits. Proteins that exhibit this behavior are known as allosteric proteins.
What is a 'Variable Cost'. A variable cost is a corporate expense that varies with production output. Variable costs are those costs that vary depending on a company's production volume; they rise as production increases and fall as production decreases. Variable costs differ from fixed costs such as rent, advertising, insurance and office supplies, which tend to remain the same regardless of production output.
Formula of Variable Cost. The formula to calculate variable cost is: Total Variable Cost = Total Quantity of Output * Variable Cost Per Unit of Output. To recognize variable costs, it is important to understand how to categorize costs.Variable costs are those which do not remain constant, specifically when production activities fluctuate.his cost per unit is the variable cost of each variable unit produced, or in other words the additional cost incurred for the production of each spark plug. For example, if the business produced 1,000 more units, it would expect to incur additional production costs of $180.