What are the three reaction pathways which pyruvate undergoes in the metabolic pathways inside the cell and what are the names of the final products of each of these pathways?
The three main reaction pathways that pyruvate can undergo in the metabolic pathways inside the cell are:
1. Pyruvate Decarboxylation: In this pathway, pyruvate is converted to acetyl-CoA through a decarboxylation reaction. This process occurs in the mitochondria and is catalyzed by the enzyme pyruvate dehydrogenase. The final product of this pathway is acetyl-CoA.
2. Anaerobic Fermentation: When oxygen is limited or unavailable, pyruvate can undergo fermentation to regenerate NAD+ for glycolysis to continue. There are two common types of anaerobic fermentation pathways:
a. Lactic Acid Fermentation: In this pathway, pyruvate is converted to lactate. This process occurs in the cytoplasm and is catalyzed by the enzyme lactate dehydrogenase.
b. Ethanol Fermentation: In this pathway, pyruvate is first converted to acetaldehyde and then to ethanol. This process occurs in the cytoplasm and involves two enzymes: pyruvate decarboxylase and alcohol dehydrogenase.
3. Krebs Cycle (Citric Acid Cycle): Pyruvate can also enter the Krebs cycle, also known as the citric acid cycle or tricarboxylic acid cycle (TCA cycle). In this pathway, pyruvate is completely broken down, releasing energy in the form of ATP and reducing coenzymes NADH and FADH2. The final products of the Krebs cycle are ATP, NADH, FADH2, and CO2.
To determine the names of the final products of each pathway, you can refer to the specific reactions and enzymes involved in each pathway.