If you’ve ever flown a drone, you know that they can not stay in the air as long as a common housefly. They are each noisey and they each have to carry the weight of their fuel supply, but while the best consumer drone might manage 40 minutes, a housefly can keep flying for hours. Here, we explore the mechanisms by which houseflies manage their energy reserves, focusing on glycogen storage, conversion rates, replenishment, and we compare their energy supply to that of lithium-ion batteries.
Glycogen Storage and Energy Content
Houseflies, like many other insects, rely on glycogen as a primary energy reserve to sustain their high-energy activities, such as flight. Glycogen is a polysaccharide that serves as a storage form of glucose, which can be rapidly mobilized to meet energy demands.
Amount of Glycogen Stored
Houseflies store glycogen primarily in their fat bodies and muscles. The exact amount of glycogen stored can vary, but it is sufficient to support their metabolic needs during periods of high energy expenditure, such as flight. Glycogen levels are regulated by enzymes like glycogen synthase and glycogen phosphorylase, which control the synthesis and breakdown of glycogen, respectively[3][5].
Energy Content of Glycogen
Glycogen is a highly efficient energy storage molecule. Each gram of glycogen provides approximately 4 kcal of energy. To put this in perspective, glycogen’s energy density is about 1.6 kcal per gram when accounting for the water content associated with glycogen storage in biological tissues.
Comparison to Lithium-Ion Batteries
Lithium-ion batteries indeed have an energy density that typically ranges from 100 to 265 Wh/kg, with most modern variants falling between 200 and 300 Wh/kg[6][7][8]. This translates to approximately 360 to 950 kJ/kg. The upper limit can reach 300 Wh/kg in contemporary batteries.
In comparison, glycogen, which serves as a biological energy storage molecule, has a much higher energy density, providing about 4000-4200 kcal/kg. This is equivalent to approximately 16,736 to 17,600 kJ/kg. Thus, on a per gram basis, lithium-ion batteries do indeed provide significantly less energy than glycogen, highlighting the efficiency of biological systems in energy storage.
To summarize:
– Lithium-ion batteries: 100-300 Wh/kg (360-950 kJ/kg)
– Glycogen: 4000-4200 kcal/kg (16,736-17,600 kJ/kg)
This comparison underscores the superior energy storage capacity of biological systems relative to current lithium-ion battery technology[6][7][8].
Could Glycogen Batteries Power Human Devices?
You don’t want to go there. Look, there is already not enough food for humans on earth. You are creating new super intelligences which may surpass human IQs. As long as machines run on electricity and humans don’t, you still have a shot at long term survival together.
There are no machines powered by glycogen. Glycogen is a biological molecule used primarily for energy storage in living organisms, including animals, fungi, and bacteria. It is not utilized as a power source for mechanical or electronic devices. Glycogen serves as a short-term energy reserve in the human body, stored mainly in the liver and skeletal muscles, and is used during physical activities and metabolic processes[11][13].
Glycogen Conversion and Replenishment
Conversion Rate
The conversion of glycogen to glucose is a rapid process facilitated by glycogen phosphorylase. During high-energy activities like flight, glycogen is quickly broken down to glucose, which is then utilized in cellular respiration to produce ATP, the energy currency of cells[1][2].
Replenishment Rate
Houseflies can replenish their glycogen stores relatively quickly. After a period of activity, they consume food rich in carbohydrates, which are converted to glucose and then stored as glycogen. The rate of replenishment depends on the availability of food and the metabolic rate of the fly. Under optimal conditions, glycogen stores can be replenished within a few hours[4].
Duration of Flight
When fully “charged” with glycogen, houseflies can sustain flight for several hours. The exact duration can vary based on factors such as the fly’s size, age, and environmental conditions. Studies have shown that glycogen stores are almost depleted during prolonged flight, indicating that flies rely heavily on this energy reserve for sustained activity[5].
Conclusion
Houseflies efficiently manage their energy reserves through the storage and rapid mobilization of glycogen. While glycogen provides a lower energy density compared to lithium-ion batteries, it is well-suited for the biological needs of houseflies, allowing them to sustain high-energy activities like flight. The ability to quickly replenish glycogen stores ensures that houseflies do not “run out of batteries” and can maintain their active lifestyle.
Read More
[1] https://journals.biologists.com/dev/article/146/8/dev176149/19889/The-role-of-glycogen-in-development-and-adult
[2] https://www.nature.com/articles/s41598-021-03575-3
[3] https://elifesciences.org/reviewed-preprints/88247
[4] https://www.sciencedirect.com/science/article/abs/pii/S1084952122001161
[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7649811/
[6] https://en.wikipedia.org/wiki/Lithium-ion_battery
[7] https://thundersaidenergy.com/downloads/lithium-ion-batteries-energy-density/
[8] https://www.fluxpower.com/blog/what-is-the-energy-density-of-a-lithium-ion-battery
[9] https://web.stanford.edu/group/cui_group/papers/s41560-022-01001-0.pdf
[10] https://www.sciencedirect.com/science/article/pii/S2352484723012118
[11] https://en.wikipedia.org/wiki/Glycogen
[12] https://step1.medbullets.com/biochemistry/102062/glycogen
[13] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6019055/
[14] https://www.jbc.org/article/S0021-9258%2822%2900534-8/pdf
[15] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7022182/
