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.
In economics, total cost is made up of variable costs + fixed costs. Variable costs (VC) are costs that change based on how many goods you produce or how much of a service you use. Fixed costs (FC) are costs that don't change from month to month and don't vary based on activities or the number of goods used.The formula to calculate total cost is the following: TC (total cost) = TFC (total fixed cost) + TVC (total variable cost). To unlock this lesson you must be a Study.com Member.he formula to calculate total cost is the following: TC (total cost) = TFC (total fixed cost) + TVC (total variable cost). To unlock this lesson you must be a Study.com Member.