Energy
Heat produced = mCΔT
Energy comes from respiration.
Calorific value - the amount of energy available
Carbohydrates are the most readily available source of energy
Fats that are non-oxidised provide the the most energy per mass.
Food is (not burned but) converted into carbon dioxide and water through oxidation.
The bomb calorimeter
Used to measure the energy content of food.
The sample of food is heated and ignited electrically. The heat given out from the combustion is transferred to a water system and the energy is calculated by the change in temperature and mass of water.
Heat produced = heat absorbed by water + heat absorbed by calorimeter
= (m x C x ΔT)water + (m x C x ΔT)calorimeter
Stirrer: to keep the water at a uniform temperature
Bomb: sealed unit where the combustion reaction occurs
Thermometer: measures the rise in temperature of water
Water: absorbs the heat of the reaction
Electric coil: heats the device to start the reaction
Cellular respiration
A set of metabolic processes that occur in the cell to convert biochemical energy from nutrients into adenosine triphosphate (ATP)
Involves catabolic redox reactions, one molecule is reduced the other is oxidised.
Adenosine Triphosphate (ATP)
- adenine group
- ribose sugar
- 3 phosphate groups
Energy that is released from combustion of carbon molecules is stored in ATP.
ATP to ADP (Adenosine Diphosphate)
- Energy released when phosphate group is released (to form ADP)
- Reversible reaction, the cell can store or release energy.
- ATP to ADP releases ~30.5 kj/mol
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