You just consumed a Frontier burrito that was the size of your head and you are wondering what your body is going to do with all that greasy goodness. Well, to put a complicated process into simple terms, cellular respiration occurs. What is cellular respiration? Cellular respiration is a series of metabolic processes that take place within a cell in which biochemical energy is harvested from organic substance (e.g. glucose) and stored as energy carriers (ATP) for use in energy-requiring activities of the cell[CF1] . That process may sound complicated still, so let’s take a closer look into what your body does after ingesting that delicious burrito.
Cellular Respiration Overview
The cell seems to “respire” in a way that it takes in molecular oxygen (as an electron acceptor) and releases carbon dioxide (as an end product), hence, the process is described to be aerobic. There are organisms that use other organic molecules as electron acceptors instead of oxygen. The type of respiration in which oxygen is not used as a final electron acceptor is referred to as anaerobic.
In anaerobic respiration (respiration in absence of oxygen), pyruvate is not metabolized by cellular respiration but undergoes a process of fermentation. The pyruvate is not transported into the mitochondrion, but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell.
Cellular respiration is essential to both eukaryotic and prokaryotic cells since biochemical energy is produced to fuel many metabolic processes, such as biosynthesis, locomotion, and transportation of molecules across membranes.
The entire process occurs in the cytoplasm of prokaryotes. In eukaryotes, glycolysis occurs in the cytoplasm whereas the Krebs Cycle (a complex energy yielding cycle drawn out below) and oxidative phosphorylation in the mitochondrion. Prokaryotic cells can yield a maximum of 38 ATP (which is the fundamental molecule that the body uses for energy) while eukaryotic cells can yield a maximum of 36.
[CF1]Maybe add a line about this being complicated too and how we can break down what breaking down looks like.
We can divide cellular respiration into three metabolic processes: glycolysis, the Krebs cycle, and oxidative phosphorylation. Each of these occurs in a specific region of the cell.
1) Glycolysis occurs in the cytosol.
Glycolysis, part of cellular respiration, is a series of reactions that constitute the first phase of most carbohydrate catabolism, catabolism meaning the breaking down of larger molecules into smaller ones. The word glycolysis is derived from two Greek words and means the breakdown of something sweet. Glycolysis breaks down glucose and forms pyruvate with the production of two molecules of ATP. The pyruvate end product of glycolysis can be used in either anaerobic respiration if no oxygen is available or in aerobic respiration via the TCA cycle which yields much more usable energy for the cell.
2) The Krebs cycle, TCA cycle or CAC takes place in the matrix of the mitochondria.
The Krebs cycle refers to a complex series of chemical reactions that produce carbon dioxide and Adenosine triphosphate (ATP), a compound rich in energy. The cycle occurs by essentially linking two carbon coenzyme with carbon compounds; the created compound then goes through a series of changes that produce energy. This cycle occurs in all cells that utilize oxygen as part of their respiration process; this includes those cells of creatures from the higher animal kingdom such as humans. Carbon dioxide is important for various reasons, the main one being that it stimulates breathing, while ATP provides cells with the energy required for the synthesis of proteins from amino acids and the replication of deoxyribonucleic acid (DNA); both are vital for energy supply and for life to continue. In short, the Krebs cycle constitutes the discovery of the major source of energy in all living organisms.
3) Oxidative phosphorylation via the electron transport chain is carried out on the inner mitochondrial membrane.
An electron transport chain (ETC) is a series of compounds that transfer electrons from electron donors to electron acceptors via redox reactions, and couples this electron transfer with the transfer of protons (H+ ions) across a membrane. This creates an electrochemical proton gradient that drives ATP synthesis, or the generation of chemical energy in the form of adenosine triphosphate (ATP). The final acceptor of electrons in the electron transport chain is molecular oxygen.
In the absence of oxygen, respiration consists of two metabolic pathways: glycolysis and fermentation. Both of these occur in the cytosol.
Who would have thought eating a burrito would be so much work?
If you want to know more about how this process works for your classes, come see us at CAPS, where we may not have burritos, but we can help you master concepts like metabolism and so much more. Visit our website for hours, locations, and services!