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Questions and Answers
What is the metabolic rate?
What is the metabolic rate?
The metabolic rate is the rate of oxidation of glucose within the body.
How many Kcal are produced from the oxidation of one mole of glucose?
How many Kcal are produced from the oxidation of one mole of glucose?
One mole of glucose produces 686 Kcal.
What is the amount of energy released per gram of glucose?
What is the amount of energy released per gram of glucose?
The energy released per gram of glucose is 3.8 Kcal/gm.
Define the respiratory quotient.
Define the respiratory quotient.
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What is the liters of O2 used per gram of glucose?
What is the liters of O2 used per gram of glucose?
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What is energy in simple terms?
What is energy in simple terms?
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State the first law of thermodynamics related to energy.
State the first law of thermodynamics related to energy.
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How does the human body relate to the conservation of energy?
How does the human body relate to the conservation of energy?
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What is the primary unit of energy in the International System of Units (S.I.)?
What is the primary unit of energy in the International System of Units (S.I.)?
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How is energy content in food typically measured?
How is energy content in food typically measured?
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Study Notes
Energy Changes in the Body
- The body produces energy through the oxidation of glucose.
- The oxidation of one mole of glucose produces 686 Kcal.
- The metabolic rate refers to the rate at which glucose is oxidized within the body.
Useful Quantities for Glucose Metabolism
- 3.8 Kcal of energy is released per gram of glucose.
- 5.1 Kcal of energy is released per liter of oxygen used.
- 0.75 liters of oxygen is used per gram of glucose.
- 0.75 liters of carbon dioxide is produced per gram of glucose.
Respiratory Quotient
- The respiratory quotient is the ratio of carbon dioxide produced to oxygen used.
- A normal person has a respiratory quotient of 1.
Energy
- Energy is defined as the ability to do work.
- Different forms of energy exist in the universe: mechanical, thermal, chemical, electrical, and nuclear.
Conservation of Energy
- Energy cannot be created or destroyed but can transform from one form to another.
- This is also known as the 1st law of thermodynamics.
Conservation of Energy in the Body
- The human body is considered an energy converter and obeys the law of conservation of energy.
- Input energy (food and body fat) is converted to output energy (work and heat loss).
Body Energy Usage
- The body utilizes food energy for:
- Operating organs.
- Maintaining constant body temperature.
- Performing work.
Units of Energy
- The joule (J) is the international system (S.I.) unit of energy.
- The erg is the French system unit of energy.
- 1 J = 10⁷ erg
- The calorie (cal) is the unit used by nutritionists to measure the energy value stored in food.
- 1 cal = 4.18 J
- 1 Cal = 1 Kcal
Factors Affecting Metabolic Rate
- The metabolic rate increases with increased physical activity.
- The metabolic rate is temperature dependent, increasing by about 10% for every 1°C increase in body temperature.
Basal Metabolic Rate (BMR)
- BMR refers to the energy needed for minimum body functions.
- BMR is approximately 92 Kcal/hr or 107 J/s (Watt).
- BMR is primarily affected by thyroid function.
- Hyperthyroidism leads to higher BMR.
- Hypothyroidism leads to lower BMR.
Maintaining Body Weight
- A constant body weight is achieved when food intake equals the energy output needed for BMR and physical activity.
- Consuming less food leads to weight loss and starvation if prolonged.
- Consuming more food leads to weight gain and obesity if prolonged.
- Fats contain the highest energy value, providing 9.3 Kcal per gram.
- Weight loss can occur by burning stored fats through diet or increased physical activity.
Work
- Chemical energy in the body is converted into external mechanical work and life-preserving functions.
- Work is calculated as the product of force and displacement: W = Force x Displacement.
- The unit of work is also the joule (J).
Power
- Power is the time rate of doing work: P = W/t.
- The S.I unit of power is the Watt (J/s).
Efficiency of the Body as a Machine
- The body's efficiency is calculated as the ratio of work done to energy consumed: E = Work done / Energy consumed.
- Muscle efficiency in external work rarely exceeds 20%.
- Climbing stairs or walking uphill work is calculated as W = mgh where mg is body weight and h is the height.
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Description
This quiz covers the fundamental concepts of energy production and metabolism in the human body, specifically focusing on glucose oxidation. Key topics include the metabolic rate, useful quantities for glucose metabolism, and the respiratory quotient, as well as the principles of energy conservation. Test your understanding of these essential biological processes.
