Why Do We Breathe Oxygen?
The air we breathe is comprised of a variety of molecules of which only 20.9% is oxygen. The average person breathes in approximately 432 liters of oxygen per day (this is equivalent to 1216 cans of soda). The tissues of the body need a minimum of 352.8 liters of oxygen per day, and this is assuming the person is at rest. The brain, which is only 2% of the body mass, needs almost 20% of the oxygen that is brought in. If the brain doesn’t receive oxygen for more than 3 minutes, the cells will begin to die. Once brain cells cease to function, permanent damage sets in.
It is a common understanding that without oxygen (O2) we will die. Hold your breath for too long and you will feel light headed. But many don’t understand why we need oxygen. Why can’t we just use carbon dioxide or some sort of other gas to survive? In order to get to the bottom of this, we have to take a look at how our body makes energy.
The body needs energy and the energy that the body requires is known as ATP (adenosine triphosphate). It is a chemical energy that the enzymes of the body recognize. Give cells another form of chemical energy like gasoline, and the cells won’t know what to do with it. It’s like hooking up an iPod to a car battery. Sure, the battery has energy, but not the type of energy the iPod can use.
Our cells work very hard to make ATP. Cells without ATP simply stop functioning and die. It’s the same thing as taking the batteries out of your television remote. It just won’t work anymore. At any given time, a cell contains about 1 billion ATP. An active cell will use approximately 2 million ATP per second. In terms of weight, all of the ATP in our bodies weighs around 50g. Interestingly enough of the 2500 calories we bring in per day, that will make up to 180 kg of ATP. But, the nice thing about ATP is that it is like a rechargeable battery. Once it is used, it can be reassembled to be used again.
If ATP is so important, how do we make it? One of the reasons we eat is to recharge the ATP. The major source of energy for the body comes from sugar. We eat the sugar, digest it into smaller sugar molecules then send these molecules to our cells. At the cellular level, the sugar molecule (more commonly referred as glucose) is sent through a series of chemical reactions to strip it free of electrons. These electrons, which have a negative charge, are shuttled to a series of proteins (electron transport chain) embedded in a specialized organelle called the mitochondria. The electrons are dropped off then travel from one protein to the next. This flow of electrons forces some of these proteins to do the job they were designed to do: serve as a chemical pump. Essentially, this is electricity within a cell. These proteins pump hydrogen ions (H+) from one compartment of the mitochondria to another.
After awhile, a high number of hydrogen ions are crammed into one area of the mitochondria and want to flow to the other area that is now low in hydrogen ions. But the only way they can get back to the other area is through a specialized protein called ATP synthase. When the H+ pass through it, they cause the ATP synthase to turn much like water through a sprinkler head. This spinning action in essence reassembles the ATP molecule, recharging it, if you will. This protein is so effective that it can make approximately 600 ATP per second. Amazing.
So you might be wondering, if this article is about oxygen, where does it come in? I’m getting to it. In order for electricity to work, the electrons must continue to flow. If they don’t flow, the pumps don’t work. If the pumps don’t work, the H+ can’t get forced to one compartment of the mitochondria. If these ions can’t get into that compartment, then they can’t flow back through the ATP synthase to recharge more ATP. If ATP is not made, the cells don't have energy to do work. If cells can’t do work, they die.
Electrons don’t jump out of the electron transport chain. They flow through and wait to be picked up. If they are picked up, more electrons can flow through. If nothing comes to remove the electrons, then a traffic jam occurs and the electrons no longer flow. It’s like cutting an electrical cord. Stopping the flow of electrons, stops the function of the device.
Oxygen loves to steal electrons. It is a chemical that is extremely electronegative, meaning it has a high attraction for electrons. The reason for its electronegativity is because of its atomic structure. I’ll save the chemistry for another day. Regardless, each molecule of oxygen gas (O2) will pick up 4 electrons and 4 hydrogen ions. This will form 2 molecules of water (H2O). Yes, believe it or not, you actually make water. Once the electrons are removed from the end of the chain, more electrons can keep on flowing leading to the recharging of more ATP. Thus, if you hold your breath, you are preventing oxygen from picking up electrons and you'll feel light headed because the cells can't function properly.
The human has evolved an advanced system to ensure you get enough of the much needed gas by setting up a method to bring in the air, creating a mechanism in the brain to sense when to breathe, designing specialized cells whose entire purpose is to carry oxygen, utilizing electrons as opposed to other chemicals, and setting it up such that when electrons are picked up harmless water is made. It all seems so perfect, too perfect. Maybe it is.
At the end of the day, the entire reason you breathe oxygen is because this gas loves to pick up electrons.