Today I am going to be explaining to you how energy is made in our body. Cool right? So make sure you’ve got enough energy to read through this post!
Before we jump into what ATP is, let’s go through the physiological processes that we go through so we can produce ATP. What is respiration? Respiration is the action of breathing and there are 3 types of respiration that are constantly happening in our bodies. First is external respiration. External respiration occurs in the lungs by diffusing oxygen into the blood stream and diffusing carbon dioxide out from the bloodstream when you breathe in and out. Then there is internal respiration. Internal respiration is an exchange of gasses between the cells of the body and the blood stream. It’s the same concept to external respiration but in your cells, not your lungs. And lastly, there is cellular respiration. Cellular respiration is the act of making ATP in a specific organelle of the cell, the mitochondria. It is how we derive energy from the foods that we eat.
What is respiration? Respiration is the action of breathing and there are 3 types of respiration that are constantly happening in our bodies. First is external respiration. External respiration occurs in the lungs by diffusing oxygen into the blood stream and diffusing carbon dioxide out from the bloodstream when you breathe in and out. Then there is internal respiration. Internal respiration is an exchange of gasses between the cells of the body and the blood stream. It’s the same concept to external respiration but in your cells, not your lungs. And lastly, there is cellular respiration. Cellular respiration is the act of making ATP in a specific organelle of the cell, the mitochondria. Actually, only 2/3 of the production of ATP occurs in the mitochondria but more on that later. Cellular respiration is basically is how we derive energy from the foods that we eat.
External and internal respiration is highly related to our pulmonary/respiratory system so I will explain it further when I post about the pulmonary system. Instead, let’s focus on cellular respiration today. The equation for cellular respiration is this.
When I said that cellular respiration is how we derive energy from food, that food specifically meant glucose. And as you can see in the equation above, glucose is the only form of food that reacts with oxygen to produce energy so it makes sense that we as humans enjoy pasta, chips, sweets, and even sugary drinks. Oxygen, on the other hand, is not something we obtain through consumption but through respiration. This is why I mentioned external and internal respiration earlier. Without oxygen, we cannot produce energy even if we have an abundance of glucose in our system so I’d say it’s pretty important we continue to breathe.
When glucose and oxygen react, the product they produce is water, carbon dioxide, and energy. The water produced gets recycled throughout your cells and the carbon dioxide leaves your body through internal, then external respiration. The energy, however, is like the currency our body requires to be able to move, grow, think, and everything else really. That currency is the topic of this post, ATP.
ATP stands for “Adenosine Triphosphate”. Its structure is comprised of a nucleotide in the form of adenosine, a sugar molecule in the form of ribose, and 3 phosphate molecules, hence the triphosphate. And as you can see in the
diagram, the energy is stored between in the phosphate molecules, in their covalent bonds that hold the phosphates together. So when the body requires energy, the covalent bond between the outermost phosphate and the center phosphate will break, releasing energy. ATP is then no longer ATP because it doesn’t have the triphosphate. So instead, it’s then called ADP- adenosine diphosphate.
Once ATP becomes ADP, is it useless then? No, ADP will eventually gain another phosphate with the help of some energy and become ATP once again as stored energy. And thankfully this is a continuous cycle because this means our bodies can efficiently gain energy without having to produce ATP from scratch every time we go to the gym.
How does ATP get produced then? Well there are 3 major steps for making ATP. Glycolysis, Krebs cycle, and oxidative phosphorylation or also called electron transport chain. Glycolysis is the first step to making ATP which is an anaerobic process. It is when a glucose molecule gets broken down into smaller pyruvate molecules in the cell’s cytoplasm, and 2 ATPs can be produced at this stage. After glycolysis is the Krebs cycle, also known as the citric acid cycle which is an aerobic process that occurs in the mitochondria of the cell. This is when pyruvate molecules get reworked to create 2 ATPs per glucose molecule. And lastly, during oxidative phosphorylation which is also an aerobic process, 34 ATPs are produced again in the mitochondria. You will notice that most of the ATPs are produced during aerobic cycles because of the presence of oxygen. This is because for example when you are performing high-intensity exercises and start running out of breath, your body cannot go past the glycolysis stage but instead goes through a side process of fermentation producing lactic acid which is the chemical that gives you pain when you try to do one too many lunges. It’s your body’s way of telling you to lay down and catch your breath. But anyways, 1 glucose molecule can produce up to 38 ATPs and this is the basics of how ATP is produced through cellular respiration.
There are other elements that go into ATP production but those are a bit more advanced and I have not learned the details of it so I will write about it when I do! Anything related to cells is difficult for me to understand since I cannot visualize it but I hope this post was easy to understand and in the next post I will write about photosynthesis which is actually the reverse equation of the cellular respiration equation! Till then y’all!