Question

What is the role of NADH + $H^+$ and $FADH_2$ that is synthesised?

Answer 1

A process in which organisms combine oxygen with food molecules to produce chemical energy to sustain life and remove waste products like carbon dioxide and water is known as cellular respiration. For the formation of chemical energy mitochondria in cells plays a very important role.

Complete answer:
Cellular respiration is a process in which organisms combine oxygen with food molecules to produce chemical energy to sustain life and remove waste products like carbon dioxide and water. In this whole process mitochondria is a very important cell organelle.
The main function of mitochondria is to convert the energy contained in food in the form of chemical bonds to energy rich compounds Adenosine triphosphate (ATP). It captures the chemical energy present in the food molecules and converts it to provide energy for other functions.

The overall process of cellular respiration is divided into three major parts:
1. Glycolysis: It is a sequence of 10 chemical reactions which converts the one glucose molecule into two pyruvate molecules. The energy released in the breakdown of glucose is stored in the form of ATP.
2. Tricarboxylic acid cycle: This process plays a major role in catabolism of organic food molecules. There are eight steps in this process with eight different enzymes. The energy produced is stored in $NAD^+$ and $FAD^+$ which are later converted to ATP.
3. Oxidative phosphorylation: In this process hydrogen atoms are removed from NADH and $FADH_2$ to form one atom of oxygen to water. This is a major mechanism in which the energy is made available to cells. This process is also known as the electron transport chain.

NADH and $FADH_2$ are the high energy compounds formed in the Krebs cycle. They are oxidised in the electron transport chain and are eventually transferred to oxygen. It generates a proton gradient and forms the synthesis of ATP by ATP synthase.

Note:
Cellular respiration is a process in which organisms combine oxygen with food molecules to produce chemical energy to sustain life and remove waste products like carbon dioxide and water. The above mentioned is the role of NADH and $FADH_2$ which are synthesised.