Question

How does an anaerobic organism that can only ferment lactose can make ATP? In detail discuss the pathways, including starting products, end products, components of ETC also talk about its transport mechanisms that was used to move the products from the enviroment into the cell.

Given the information describe how the organisms would make ATP in the environment they are found. Make sure to discuss in detail each of the pathways, including the starting products, end products, components of the ETC (if applicable), how the cell makes ATP during this process, where in the cell each of these pathways occur and the transport mechanism(s) utilized to move the starting products from the environment into the cell.

Answer 1

The process occurring in anaerobic condition (absence of oxygen) is an anaerobic fermentation where the end product is lactic acid. Lactic acid fermentation is a metabolic process by which glucose and other six-carbon sugars (sucrose or lactose) are converted into cellular energy (ATP) and the metabolite lactate, which is lactic acid in solution. It occurs in some bacteria and animal cells, such as muscle cells.

Fermentation process does not involve an electron transport system (ETC) and does not directly produce any additional ATP beyond that produced during glycolysis by substrate-level phosphorylation.

- There are different anaerobic fermentative reactions.

1. Fermentative anaerobic organisms mostly use the lactic acid fermentation pathway:

C6H12O6 + 2 ADP + 2 phosphate → 2 lactic acid + 2 ATP

The energy released is conserved in regenerating two ATP from ADP molecule per glucose.

(Starting product is glucose

End product is lactic acid)

Eg. Bacteria

2. Plants and fungi (like yeasts) use alcohol (ethanol) fermentation when oxygen supply is less.

C6H12O6 (glucose) + 2 ADP + 2 phosphate → 2 C2H5OH + 2 CO2↑ + 2 ATP

(Starting product is glucose

End product is ethanol)

- Muscle cells also carry out lactic acid fermentation, though only when they have too little oxygen supply for aerobic respiration to process. The Cori cycle (also known as the lactic acid cycle is a metabolic pathway in which lactate produced by anaerobic glycolysis in muscle cells is transported to the liver and converted to glucose, which then returns to the muscles and is metabolized back to lactate. Muscular activity requires ATP, which is provided by the breakdown of glycogen in the skeletal muscles. When the supply of oxygen is sufficient, thE energy comes from pyruvate( glycolysis) into the citric acid cycle. But when oxygen supply is insufficient, during excessive muscular activity, energy is released through anaerobic metabolism and  Lactic acid fermentation occurs which converts pyruvate to lactate by lactate dehydrogenase. Instead of accumulating inside the muscle cells, lactate produced by anaerobic fermentation is taken up by the liver and then gluconeogenesis ( glucose formation) occurs.