Lecture 20 Flashcards
What is catabolism and anabolism?
ATP is hydrolysed to ADP and P to do cellular work, these processes are known as anabolism. The production of ATP from ADP and P with energy from food is known as catabolism.
What are the energy equations of the body? How else can we lose energy?
Energy intake = energy expended + energy stored.
Energy expended = basal metabolism + activities. A small amount of energy is also lost in urine and sweat.
Give an example of genetic components of weight gain.
There are genetic components to weight gain, an example of this is in mice with deficient leptin they eat more and hence become obese.
What are the typical energy units for metabolism?
How do we determine the energy contents of food?
The unit of energy is the joule and 1 cal = 4.184 J, 1 Cal (capitalised) = 4.184 kJ. We determine the energy content of foods via bomb calorimetry (the energy released by burning the food)
Where do we lose some of the energy in our food calculated during bomb calorimetry and what are the atwater factors?
Not all the energy in food is available due to: loss in faeces due to cellulose, and nitrogen which isn’t oxidised (urine). The total energy for different food types after these are:
Fat = 38 kJ/g, carbohydrate = 17 kJ/g, protein = 17 kJ/g and ethanol = 29kJ/g. These are known as atwater factors and can be used in combination with chemical compositions of foods to calculate the total energy.
How is energy expenditure measured?
Energy expenditure measuring is done via direct calorimetry, it works by measuring heat output from individual in a whole body calorimeter (particularly good for basal metabolic rates) It can also be measured via indirect calorimetry (this works based on the oxygen consumption and carbon dioxide respiration in combination with the equation for metabolism.
Each litre of oxygen consumed is 20.9 KJ of energy.
What is the respiratory exchange ratio.
The respiratory exchange ratio is the carbon dioxide produces / oxygen taken in. This will vary based on the fuel used (and activity) and can be calculated with indirect calorimetry.
What is basal metabolism?
The basal metabolism is the energy required for maintenance of life and involves muscle contractions, nerve conductions, ion transport, synthesis of macromolecules, maintenance of body heat (this is the energy expenditure at rest). It is affected by many factors e.g gender, age, body size and composition, genetics, hormonal status. It can also be changed by many factors.
What are hypo and hyperthyroidism?
Hyperthyroidism is the result of a heightened basal metabolism and hypothyroidism is the result of a lowered amount.
