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Questions and Answers
What does metabolism represent?
What does metabolism represent?
Which of the following is a catabolic reaction?
Which of the following is a catabolic reaction?
What is the main energy currency stored during catabolic reactions?
What is the main energy currency stored during catabolic reactions?
Which form of energy is responsible for maintaining body temperature?
Which form of energy is responsible for maintaining body temperature?
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An anabolic reaction involves:
An anabolic reaction involves:
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What defines metabolic rate?
What defines metabolic rate?
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Study Notes
Metabolism
- Chemical reactions within body cells.
- Two main types: catabolic and anabolic.
Catabolic Reactions
- Break down complex food molecules (proteins, fats, carbohydrates).
- Produce simpler molecules and energy:
- Chemical energy (ATP): used for muscle contraction, cellular processes.
- Heat energy: maintains body temperature.
Anabolic Reactions
- Synthesize complex molecules from smaller ones.
- Proteins from amino acids.
- Fats from fatty acids.
- Glucose from lactic acid.
Metabolic Rate
- Amount of heat released per hour during chemical reactions.
- Measured in calories (kilocalories or Calories): heat to raise 1 kg water by 1°C.
- Energy equivalent of O2:
- Carbohydrates: 5 calories/liter O2
- Fat: 4.7 calories/liter O2
- Protein: 4.5 calories/liter O2
- Mixed food: 4.8 calories/liter O2
Measuring Metabolic Rate
- Direct Calorimetry: measures heat lost by a subject in a calorimeter.
- Indirect Calorimetry: calculates heat produced from O2 consumption (MR = O2 utilized (liters/hour) × 4.8).
Energy Balance
- In healthy adults, energy intake equals energy output.
- Energy output includes:
- Internal work: metabolic functions, digestion, temperature regulation.
- External work: physical activity.
Specific Dynamic Action of Food (SDA) / Thermal Effect of Food (TEF)
- Energy used to digest, absorb, and metabolize food.
- Contributes to daily calorie expenditure.
- Starts one hour after eating, lasts 4-12 hours.
- Factors affecting TEF: age (decreases with age), physical activity (increases TEF), meal size, composition, frequency, processing, and external temperature.
- Proteins have the highest TEF.
- TEF is directly proportional to food intake.
- TEF decreases at low temperatures and increases at high temperatures.
Total Energy Expenditure
- Includes internal and external work plus TEF.
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Description
Test your knowledge on metabolism and its key processes including catabolic and anabolic reactions. Explore how these reactions contribute to energy production and metabolic rate measurement. Perfect for students learning about cellular biology.
