All cells must perform cellular respiration to get energy and stay alive, but not all organisms can do aerobic cellular respiration.
Find out in this lesson if prokaryotic organisms can use oxygen to do cellular respiration and how the process works.
What are prokaryotes? They are simple, usually single-celled organisms. Prokaryotic cells do not have a nucleus; instead the DNA is packed up in the middle of the cell.
They also have ribosomes to make proteins and a membrane and cell wall to contain the contents of the cell. Prokaryotes do not have specialized organelles like the more complex eukaryotes (like us humans).Prokaryotes include bacteria, those organisms you hear about on the news causing rampant disease and destruction (but most of them are not so bad).
The other kind are archaea, which usually live in extreme environments that are too hot, cold, salty, or alkaline for other cells to live. Whether they live inside your body or inside a hot spring, prokaryotes must do cellular respiration to stay alive.When you hear the word ‘respiration’, you probably think of breathing.
Well, cellular respiration is not the same thing as breathing. It’s actually a metabolic process that involves breaking apart glucose (sugar) to create a form of cellular energy called ATP.All organisms do cellular respiration to stay alive, but they don’t all do the same type of cellular respiration.
You see, there are both aerobic cellular respiration (with oxygen) and anaerobic respiration (without oxygen). The main difference is that aerobic produces much more energy. Eukaryotes need to do aerobic cellular respiration (and we breathe to get that necessary oxygen!), but prokaryotes are much simpler, so anaerobic cellular respiration is often sufficient. But is it enough all the time? No!So, the answer to our question is…Yes! Aerobic cellular respiration does happen in prokaryotic organisms.
But only certain kinds. Let’s examine this process.
Aerobic Cellular Respiration
In your cells, cellular respiration happens in a special organelle called the mitochondrion. But as mentioned, prokaryotic organisms don’t have organelles. Rather than taking place in the mitochondrion, cellular respiration happens either in the cytoplasm or across the plasma membrane of the cell. Scientists believe that the mitochondria in our cells are actually bacteria that moved in to perform cellular respiration for us.
The first step of cellular respiration, whether it is aerobic or anaerobic, is called glycolysis (glyco= glucose, lysis= split apart).
This happens in the cytoplasm in both eukaryotic and prokaryotic cells and splits glucose, or sugar, into two molecules in order to make ATP.Then, there are two more steps that only occur during aerobic respiration.
The Krebs cycle (also called the citric acid cycle or the TCA cycle) finishes breaking the sugar down into carbon dioxide.
As the remnants of glucose are being broken apart, energized electrons are released.
These electrons move to the electron transport chain, where they are passed to a bunch of different carriers across the cell membrane in prokaryotes. In eukaryotes, this movement of electrons happens across the mitochondrial membrane.This movement causes a build up of negatively charged electrons on one side of the membrane and a build up of positively charged protons on the other side. Have you ever heard the phrase ‘opposites attract’? Well, they do, and these protons and electrons really want to be together. When the electrons reach their final carrier, oxygen, they can finally move back across the membrane to be with their proton soul mates.
This movement is what helps the cell make lots of ATP, meaning the electron transport chain is the main producer of ATP during cellular respiration.Note: The Krebs cycle does not use oxygen directly, but it works in conjunction with the electron transport chain. The electron transport chain uses oxygen directly, so the Krebs cycle also requires oxygen, albeit indirectly.
Examples of Prokaryotes
As mentioned above, different prokaryotes can perform either aerobic or anaerobic respiration.
Some examples of bacteria that only do aerobic respiration, and are therefore called obligate aerobes, are Staphylococcus species, which can cause a variety of infections in humans, and Mycobacterium tuberculosis, which, as its name implies, causes tuberculosis.Other prokaryotes perform anaerobic respiration, but will switch to aerobic when oxygen is present. E. coli, that bacteria you may hear about on the news causing food-poisoning outbreaks, is one of these facultative anaerobes.But not all prokaryotic cells can perform cellular respiration, especially if there’s no oxygen around! The bacteria in your stomach, for example, don’t have any oxygen available to perform aerobic cellular respiration. These cells can do anaerobic respiration, also called fermentation, which basically just involves repeating glycolysis.
Prokaryotes, however, can make a whole bunch of different products during fermentation, such as ethyl alcohol.
Aerobic cellular respiration uses oxygen to make ATP, a form of energy the cell can easily spend to do work. Many prokaryotes, small simple cells like bacteria, can perform aerobic cellular respiration.
These cells will move electrons back and forth across their cell membrane. Other types of prokaryotes cannot use oxygen to perform cellular respiration, so they perform anaerobic respiration.