The key difference between pentose phosphate pathway and glycolysis is that pentose phosphate pathway is a metabolic pathway that produces NADPH and ribulose 5 phosphate at the end of the process, while glycolysis is a metabolic process that produces ATP, NADH, and pyruvate at the end of the process.
Pentose phosphate pathway and glycolysis are two metabolic pathways. Both pathways produce energy. In the pentose phosphate pathway, ribulose 5 phosphate generates from glucose 6 phosphate. This ribulose 5 phosphate can be used to generate DNA and RNA. Moreover, this pathway produces NADPH rather than ATP. On the other hand, in glycolysis, pyruvate generates from glucose. In addition, ATP and NADH are produced at the end of glycolysis.
CONTENTS
1. Overview and Key Difference
2. What is Pentose Phosphate Pathway
3. What is Glycolysis
4. Similarities – Pentose Phosphate Pathway and Glycolysis
5. Pentose Phosphate Pathway vs Glycolysis in Tabular Form
6. Summary – Pentose Phosphate Pathway vs Glycolysis
What is Pentose Phosphate Pathway?
Pentose phosphate pathway is a pathway that occurs parallel to glycolysis. This pathway produces NADPH, pentoses (5 carbon sugars), and ribulose 5 phosphate. Ribulose 5 phosphate is a precursor for the synthesis of nucleotides. This pathway was discovered by Otto Warburg in the 1930s. The pentose phosphate pathway is not involved in the oxidation of glucose. It is an anabolic process that is especially important for red blood cells. The pentose phosphate pathway takes place in the cytosol in most organisms. However, in plants, most of the pentose phosphate pathway steps happen in plastids.
Figure 01: Pentose Phosphate Pathway
The pentose phosphate pathway divides into two different phases: oxidative phase and non-oxidative phase. The oxidative phase generates NADPH, while the non-oxidative phase generates 5 carbon sugars. The reactions of this pathway are enzymatically catalyzed. But it can also occur non-enzymatically in extreme conditions such as the Archean ocean. In extreme conditions, the pentose phosphate pathway is catalyzed by metal ions such as ferrous (Fe (II).
What is Glycolysis?
Glycolysis is a metabolic pathway that extracts energy from glucose by splitting it into two pyruvate molecules. The energy released by this process is used to generate high-energy molecules such as ATP and NADH. In most organisms, glycolysis takes place in the cytosol of the cell. Glycolysis was discovered by Gustav Embden, Otto Meyerhof, and Jakub Karol Parnas in the 1930s. Therefore, it is also called Embden Meyerhof Parnas (EMP) pathway. The glycolysis can be divided into two distinct phases: investment phase and yield phase. Investment phase consumes ATP, while yield phase produces ATP.
Figure 02: Glycolysis
At the end of the glycolysis, 2 ATP, 2NADH, and 2 pyruvate molecules are generated. If oxygen is available, pyruvate fully breaks down to CO2 in cellular respiration, which makes many more ATP. Furthermore, NADH passes its electron to the electron transport chain, which leads to more ATP generation.
What are the Similarities Between Pentose Phosphate Pathway and Glycolysis?
- Pentose phosphate pathway and glycolysis are two metabolic pathways.
- Both pathways are parallel to each other.
- In both pathways, energy is produced.
- Both pathways were discovered in the 1930s.
- The starting compound of both pathways is a 6 carbon molecule.
- Both pathways can be identified universally in all organisms.
- They mainly occur in the cytosol.
- Both pathways have a very ancient evolutionary origin.
What is the Difference Between Pentose Phosphate Pathway and Glycolysis?
Pentose phosphate pathway is a metabolic pathway that produces NADPH and ribulose 5 phosphate while glycolysis is a metabolic process that produces ATP, NADH, and pyruvate. Thus, this is the key difference between pentose phosphate pathway and glycolysis. Furthermore, the pentose phosphate pathway is not involved in the oxidation of glucose, while glycolysis is involved in the oxidation of glucose.
The following table summarizes the difference between pentose phosphate pathway and glycolysis.
Summary – Pentose Phosphate Pathway vs Glycolysis
Pentose phosphate pathway and glycolysis are two parallel metabolic pathways discovered in the 1930s. They are extremely important for the survival of organisms. The pentose phosphate pathway produces NADPH and ribulose 5 phosphates at the end of the process. However, the pentose phosphate pathway is not a regular part of cellular respiration. Glycolysis produces ATP, NADH, and pyruvate at the end of the process. It is the main process of cellular respiration. So, this is the summary of the difference between pentose phosphate pathway and glycolysis.
Reference:
1. “Pentose Phosphate Pathway.” An Overview | ScienceDirect Topics.
2. “Biochemistry, Glycolysis.” Statpearls. NCBI Bookshelf.
Image Courtesy:
1. “Glycolysis” By This W3C-unspecified vector image was created with Inkscape. – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Pentose Phosphate Pathway” By GdenBesten – Own work (CC BY-SA 3.0) via Commons Wikimedia