Question

What are the products of Glycolysis in cellular respiration?

Answer 1

Hint: Glycolysis is the first step in cellular respiration and the breakdown of glucose. There are two steps in glycolysis: (i) the Energy-requiring phase and (ii) the energy-releasing phase. The end products of glycolysis are the initial electron acceptors of Krebs’s cycle.

Complete answer:
Glycolysis is also referred to as the Embden-Meyerhof-Parnas pathway or the glycolytic pathway. It is a ten-step process that takes place in the cytosol of eukaryotic cells. The glucose molecule is broken down which is why it is called ‘sugar splitting’. The energy released by the splitting of glucose is stored in the form of ATP. Glycolysis can occur either in the presence of oxygen or the absence of oxygen.
One molecule of glucose releases four ATP’s out of which two are consumed in the preparatory phase. To cleave the glucose molecule, it is phosphorylated to decrease its stability to form two pyruvate molecules. By substrate-level phosphorylation 4 Phosphate groups are transferred to ADP to generate 4 ATP and 2 NADH molecules.
The general reaction of glycolysis is as shown below:
$Glu\cos e\text{ + 2 NA}{{\text{D}}^{+}}\text{ + 2 }{{\text{P}}_{i}}\text{ + 2 ADP}\to \text{ 2 Pyruvate + 2 }{{\text{H}}^{+}}\text{ + 2NADH + 2 ATP + 2 }{{\text{H}}^{+}}\text{ + 2 }{{\text{H}}_{2}}\text{O + Energy }$
Now, let’s understand the process of glycolysis briefly-
Initially the 6 carbon molecule- Glucose is phosphorylated to glucose-6-phosphate using 1 ATP. It is done because Glucose-6-phosphate is more reactive than glucose. Also, the former gets trapped in the cell since phosphorylated glucose can’t escape through the membrane.
In the second step, Glucose-6-phosphate is converted to Fructose-6-phosphate. This Fructose-6-phosphate is also phosphorylated to generate Fructose 1,6-bisphosphate using extra ATP.
Thus, Fructose 1,6-bisphosphate splits into two molecules of 3 carbons i.e. pyruvate. These pyruvate molecules enter the mitochondria from the cytosol after conversion into Acetyl coenzyme A.
Therefore, the end products of Glycolysis are: 2 Pyruvate, 2 NADH, and 2 ATP molecules.

Note:
During aerobic respiration, pyruvate can be used to form carbon-di-oxide and many molecules of ATP. During glycolysis, always remember that the most important step is the phosphofructokinase reaction as it is controlled by the energy currency of the cell-ATP.