1. Nutritive Value of food
Sources and uses of food energy
Metabolism Cell respiration
Oxygen + glucose = energy + water + carbon dioxide
The waste products are water and carbon dioxide.
The energy obtained through cell respiration (38ATP) can be used as:
1. Mechanical energy is for movements of the whole body and organs
2. Heat is needed to keep the body temperature constant.
3. Chemical energy is present in all metabolic reactions.
4. Electrical energy is to transmit nerve impulses.
Energy Balance:
Energy input from the food eaten = Energy output (Basal Metabolism +Physical Activity)
Basal Metabolism: it is the energy required to keep the body functioning
(age, sex, body size like height and weight and the state of the body).
One kilocalorie is the energy needed to raise the temperature of 1 kg of
pure water to 1 degree centigrade.† The energy contained in food is
measured in kilocalories:
1 g of carbohydrates = 4 kcal
1 g of proteins = 4 kcal
1 g of fats = 9 kcal
1. Calculate the energy provided by yogurt (100 g) if its chemical
composition is 14% carbohydrates, 3% proteins, 3% fats.
2. Calculate caloric value of 250 g red meat, if its chemical composition
is 20% protein, 5 % fats.
3. Reading labels.