A) atp is produced by cellular respiration in your human body cells. there are a variety of enzymes that work to produce atp, but one of those enzymes is called phosphofructokinase-1. this enzyme is sensitive to blood acidity. blood can become more acidic if a patient is in respiratory distress. 4. variable affecting enzyme function:

An enzyme is sensitive to the environmental conditions. It is affected by various chemical and physical factors. Changes in the environmental factors denatures the enzyme.

4 Variable affecting an enzyme function are as follows:
1. pH: An enzyme is affected by change in pH. Every enzyme has its own specific pH at which it works ideally. 
2. Temperature: An enzyme works best at ideal temperature. Increase or decrease in the temperature causes denaturation of enzyme.
3. ATP: Increase or decrease in the amount of ATP also affects the function of an enzyme.
4. Product: Increase or decrease in the amount of product also affects the ideal functioning of an enzyme. 

Blood acidity is a variable which affects the functioning of the enzyme phosphofructokinase-1. Blood acidity can increase if a patient is in respiratory distress, making respiratory distress another variable which effects the functioning of the enzyme.