Process of Cellular Respiration in Bacteria

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  • 0:03 What Is Cellular Respiration?
  • 1:05 Preparing for Cellular…
  • 3:07 What Is the Electron…
  • 5:13 Lesson Summary
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Lesson Transcript
Instructor: Erika Steele

Erika has taught college Biology, Microbiology, and Environmental Science. She has a PhD in Science Education.

Bacteria, like all living organisms, needs energy to survive. This lesson will explain how bacteria break down nutrients to generate energy using cellular respiration.

What Is Cellular Respiration?

Not too many of us think about the survival of bacteria or how it takes place. All living organisms need ways to get nutrients and energy, including bacteria. Cells are able to acquire energy in a wide variety of ways, including cellular respiration. Cellular respiration is a process that uses oxygen, nitrate, or sulfate to break down nutrients to generate a cell's energy. If oxygen is used, it is called aerobic cellular respiration. If oxygen is not used, it is called anaerobic cellular respiration.

In the process of breaking down nutrients such as glucose, carbon dioxide and water are generated. Carbon dioxide and water are waste products of aerobic cellular respiration. When people exhale carbon dioxide (CO2), or sweat, you are seeing by-products of cellular respiration in human cells. Bacteria does the same thing, it just doesn't breathe or sweat, so we don't usually think about it generating energy in the same way we do.

Preparing for Cellular Respiration

Cells, including bacteria, can be thought of as energy producing factories that take nutrients and convert them into energy called adenosine triphosphate (ATP). Some cells may be better than others at producing ATP because they use more efficient methods. The benefit of using cellular respiration for bacteria is the amount of energy or ATP generated. The reason cellular respiration generates so much ATP is because it maximizes the use of glucose by using by-products generated in other energy producing pathways.

Glycolysis is the first step in breaking down glucose to obtain energy through cellular respiration in bacteria. This set of reactions occurs in the cytoplasm of bacteria. The product of glycolysis, pyruvate, can be broken down further to generate even more energy. Two possible outcomes for pyruvate are the Krebs cycle or fermentation. Fermentation generates some energy for the cell, but it also generates toxic products like alcohol, acetic acid (or vinegar), and lactic acid that have to be cleaned up, or removed from the cell. This process can be compared to burning coal for energy; energy is provided, but it is pretty bad for the environment. Respiration, on the other hand, could be compared to solar or wind energy. It takes the same product, pyruvate, and extracts energy from it in a way that is 'cleaner' for the cell, and in turn generates more energy.

The Krebs cycle, also called the citric acid cycle, is the second preparatory step for cellular respiration in aerobic bacteria. The Krebs cycle also occurs in the cytoplasm of bacteria. In the Krebs cycle, pyruvate is broken down into carbon dioxide. In addition to generating ATP, the Krebs cycle and glycolysis generate hydrogen ions (H+), and electrons as shown in this figure. The electrons and H+ are harvested in cellular respiration to generate energy on the electron transport chain.

glucose metabolism

What Is the Electron Transport Chain?

Cellular respiration requires the electron transport chain, or ETC, which is a series of enzymes that pump electrons and hydrogen (H+) generated in glycolysis and the Krebs cycle, out of the cell for ATP synthase to synthesize ATP. Both the ETC and ATP synthase are located in the plasma membrane. Electron carriers such as NADH and FADH2 move the hydrogen ions and electrons from the cytoplasm to the plasma membrane to optimize energy production.

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