Metabolism

Question 1

1st Law of Thermo Dynamics

Answer 1

• Total energy within a system is constant i.e. energy can neither be created or destroyed
  
  • In the body: Eintake (food) = Eexpended + Estored (weight gain)
  • Eexpended is due to basal metabolism and activities
  • Excess energy is stored as fat
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Question 2

Leptin

Answer 2

Hormone that controls how much we eat, affects brain and makes us think we are full.
Eat a lot more if missing.

Question 3

Measuring Energy

Answer 3

• Can measure by combusting in bomb calorimeter.
• Not all energy in food is available (lost in faeces, nitrogen not oxidised etc. adjust for these factors)
  Energy output for:
• fat = 38 kj/g
• Carbohydrates = 17kj/g
• Protein = 17 kj/g
• Ethanol = 29 kj/g

Question 4

Direct calorimetry

Answer 4

measuring heat output of an individual in a whole body colorimeter.
- Good for determining BMR

Question 5

Indirect calorimetry

Answer 5

Based on O2 consumption and CO2 output measured in respirometer.

• Allows calculation of energy expenditure in a range of activities.
• Respiration exchange ratio(RER) = CO2 produced/O2 consumed.

Question 6

Basal Metabolism

Answer 6

• Energy required for maintenance of life (Muscle contraction, nerve conduction etc.)
• Defined as energy expenditure at rest
• Differ based on gender, age, body size and composition, genetics etc.
• Increased by athletic training, late pregnancy, fever, Hyperthyroidism.
• Decreased by malnutrition, sleep, drugs, Hypothyroidism