Background: You are working as an intern in a small biotechnology company that i
ID: 173989 • Letter: B
Question
Background:
You are working as an intern in a small biotechnology company that is trying to develop genetic engineering approaches to improve the ability of humans to swim under water without SCUBA equipment or other sources of oxygen. As a physiologist, you realize that this problem has already been solved by marine mammals and birds who are able to function under water for extended periods of time. You decide to do some background research on diving mammals and birds and prepare a list of possible strategies to present at the next research staff meeting.
Question:
State two possible strategies for enhancing the ability of humans to function under water without access to additional oxygen and briefly discuss why you think each strategy would be effective.
Explanation / Answer
Ans:
Possible strategies for enhancing the ability of humans to function under water without access to additional oxygen are mentioned herunder.
· Increased positively charged proteins called myoglobin (can store oxygen) oxygen binding site.
· This can be achieved by a person who had a mutation that granted them the possibility to produce myoglobin at levels higher than 8g/kg.
· Increased level of haemoglobin content
· Controlled breathing, liquid/water breathing
1. Explanation: Diving mammals—including whales, seals, otters, and even beavers and muskrats—have positively charged oxygen-binding proteins, called myoglobin, in their muscles. Positively charged oxygen-binding proteins, called myoglobin, in their muscles. This positive characteristic allows the animals to pack much more myoglobin into their bodies than other mammals, such as humans—and enables diving mammals to keep a larger store of oxygen on which to draw while underwater.
The above strategy could also be applicable to humans. In humans Myoglobin is a protein that stores O2 for auxiliary use in cells. Since Oxygen is the limiting factor in muscle performance in normal humans. A person who had a mutation that granted them the possibility to produce myoglobin at levels higher than 8g/kg. As per the literature, this change doesn't outright kill the human. Sperm whales evolved to invest a lot of energy into making a protein that allows them to hunt. In humans this somehow does not stunt or kill the person.
Myoglobin is useful for sperm whales and other aquatic mammals, but if I am live on the surface hemoglobin is much more useful. The challenge in getting oxygen to our cells is that oxygen does not like to dissolve in water. As our blood moves through our lungs, the partial pressure of oxygen will determine the oxygen concentration, but because of the low solubility of oxygen this isn't a very high concentration in the water itself (less than mM). When the blood moves by our cells the effective partial pressure of oxygen is lower so the oxygen diffuses in. To make an analogy to electronics, our blood is a weak capacitor that charges to a certain "voltage" (partial pressure O2) in our lungs, moves to our cells, and then partially discharges to bring their voltage up close to what exists in the lungs. This would be more efficient if we could increase the "capacitance" of our blood. That is what red blood cells do. Red blood cells have hemoglobin, a protein that binds oxygen. The lets the blood absorbs more "charge" (i.e. oxygen) in the lungs, and when the blood makes it to the cells more charge is transferred. For a normal capacitor the charge transferred will be proportional to the voltage drop. Adding more red blood cells can increase the capacitance. But what if we could design a nonlinear capacitor that transferred more charge? That is actually what hemoglobin does. The "charge" (amount of oxygen) that loads onto hemoglobin is proportional to something like voltage or so. This relationship is given by the Hill equation. By comparison, myoglobin behaves like a normal capacitor (the Hill coefficient is one). That is why hemoglobin useful for transporting oxygen to our cells. In fact, this is the reason why athletes train at high altitude. It forces our body to make more hemoglobin to deal with the lower partial pressure of oxygen. It is also why some cyclists try to use blood doping, where they save some blood, spin it down to concentrate the red blood cells, and inject it back before a race. But we also have myoglobin on our muscle cells and creates an "extra capacitor" for our cells. Hemoglobin in the blood can charge this capacitor up, but if you hold our breath the myoglobin is going to make sure our cells keep some oxygen to spare. If you had more myoglobin, you could hold our breath longer. But this isn't as easy to change. Myoglobin in a variety of aquatic mammals has evolved to contain a higher surface charge, which is thought to let them pack more myoglobin into their cells without forming aggregates.
Breathing a liquid instead. Not pure liquid oxygen: at -200C, it would turn you into a human popsicle from the inside out and shatter your lungs the moment you tried to breathe. Instead,fluids that are rich in dissolved oxygen. A class of chemicals known as perfluorocarbons (PFCs) can dissolve high concentrations of oxygen and carbon dioxide, and are liquid at much more comfortable temperatures.
Eg. Perfluorocarbons are attractive because they are colourless, odourless, and non-toxic – much like air – and because they would allow divers to withstand high pressures when escaping from crippled submarines. Experiments in the 1960s showed that mice and cats submerged in perfluorocarbon liquids could survive for days breathing the oxygenated fluid. As the fluid holds for more oxygen than the same volume of air, theoretically you might be able to hold your breath a lot longer with one lungful of perfluorocarbon. However, the delicate structures of mammal lungs are not designed to withstand the force necessary to push four litres of liquid in and out of the body, making them a poor substitute for air over long periods, though liquid breathing has found some use in treating premature babies, whose lungs are not yet able to inflate on their own.
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