Nutritional physiology - lectures week 4

Week 4: Whole body metabolism & thermoregulation
Energetic efficiency of metabolic conversions (heat as byproduct)




Regulation
- Options
- Consequence
- Limitations

Thermodynamics
1. Law of conservation energy
a. energy cannot be created or destroyed
b. only transferred or transformed
2. All forms of energy are quantitatively convertible to heat
a. heat is the lowest energy form
b. All energy transactions have a tendency to reach lowest energy form

ATP: production and use

, S + O2 → ATP + CO2 + H2O + (B) + Heat

- S Substrate Carbo’s, fat, protein
- O2 Oxygen Aerobic, anaerobic
- CO2 Carbon dioxide Hypo- hypercapnia/carbia
- H2O Water Metabolic water
- B By product Lactate, NH3, urea
- ATP Currency Oxid-P, Substr-P
- Heat Metabolic heat In-efficiency, loss of ME

RER / RQ = respiratory exchange ratio / respiratory quotient = CO2 / O2
RER → breathing, RQ → blood measurement

Aerobic respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O + 2816 kJ /mol
→ no B
→ 35% of ME in ATP, 65% heat (same for glycogen, fat, carbs)
→ RER = 6/6 = 1

An-aerobic respiration
C6H12O6 → 2 Lactate + 88 kJ / mol
→ B = lactate, no O2, CO2, H2O
→ 75% of ME in ATP, 25% heatS
Glucose from glycogen, energy production & efficiency even higher
Fat and protein cannot be used

Overview




Speed
Anaerobic is faster than aerobic respiration
Exercise → anaerobic in muscles → lactate accumulation