Final answer:
The Basal metabolic rate (BMR) is the energy expended to maintain resting functions like respiration and circulation, accounting for about 70-75% of daily energy use.
Step-by-step explanation:
The energy we expend just to maintain our resting functions, such as respiration and circulation, is known as the Basal metabolic rate (BMR). This is the total energy conversion rate of a person at rest, essential for sustaining life's processes including heart rate, kidney function, and more. The BMR can vary based on factors such as age, gender, body weight, and muscle mass, and represents about 70-75% of our total daily energy expenditure. It is measured under specific conditions: a person being at rest, in a comfortable temperature and humidity, awake but not engaged in activity, and having fasted for 10-12 hours. *BMR* is directly proportional to oxygen consumption, as the metabolic processes are an oxidizing of food, and typically, around 20 kJ of energy is produced for every liter of oxygen consumed by the body.