Karteikarten
Mechanical Efficiency of the Cycling Human
Karten in diesem Stapel (12)
- 1Are the processes transforming one energy source to another (e.g. glucose to ATP) and the mechanisms by which ATP is used to power cellular reactions 100% efficient?No, and the energy is primarily lost as heat. The final product of all the body's metabolism is heat, which is why metabolism is measured in calories (the amount of heat required to raise the temperature of 1kg of water by 1 degree).
- 2At rest, why is the body 0% efficient?Because it is not doing any work, so ultimately all of its energy is going into the production of heat. We are being kept alive, but we are not doing anything active.
- 3How does one calculate mechanical efficiency?(Useful work / total energy expenditure) x100%
- 4Why can the body's 'useful' power output be easily measured on a bicycle ergometer?Because it provides a fixed resistance at which to work against.
- 5What value is used to estimate one's metabolism's total energy production?Metabolic rate (CO2 production and O2 consumption, as these are consumed and produced by oxidative phosphorylation which in turn creates ATP needed for metabolism).
- 6Put these in order of increasing mechanical efficiency: human, steam train, petrol car, steam engine, electric train, diesel engine.Steam train (5%), steam engine (15%), human (~19% from our lab results), petrol engine (22%), diesel engine (32%), and electric train (80%).
- 7Under what conditions did you collect air breathed by the subject in this experiment?At rest (for 5 minutes), cycling at 50rpm against 1kg for 5 minutes (air collected in last minute), cycling 50rpm against 2 kg for 5 minutes (air collected in last minute), and cycling at 50rpm against 3 kg for 5 minutes (air collected in last minute).
- 8What type of bag was used to collect the air from the subject?A Douglas bag.
- 9The volumes of gas collected must have their values corrected for environmental conditions - such as?Atmospheric pressure, temperature, and the presence of water vapour.
- 10In this lab, metabolic rate was calculated using a spreadsheet rather than by hand. Next, the metabolic rate (cal/hour) needed to be converted into useful work done - how is this calculated?The metabolic rate at each interval (rest, and then increasing exercise intensity) was calculated as calories/hour. The number of calories was converted to joules (1 Cal = 4187 joules) and this number was divided by the number of seconds in an hour (3600) to get joules/sec, the units of useful work done.
- 11How was gross mechanical efficiency calculated once the metabolic rate and useful work done had been calculated?(useful work/metabolic rate) x100
- 12Why is the net mechanical efficiency calculated as a final value, instead of using the initial gross mechanical efficiency calculated?Because the gross mechanical efficiency is the baseline work that the body does for life PLUS that that it was doing in the exercise that was measured. In order to only measure the work being doing for the exercise and therefore measure the actual (net) mechanical efficiency, the resting metabolic rate was subtracted from the working metabolic rates calculated, and mechanical efficiency ((useful work/metabolic rate)x100) was calculated again. This yielded higher (more efficient) results.
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- From the 17-02-14 Human Physiology lab.
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- sophietevans
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