Question

What is cellular respiration?

Answer 1

When we breathe, we take in oxygen-rich air and exhale carbon dioxide-rich air. When we breathe in, oxygen-rich air is carried to all regions of our body, eventually reaching each cell. With the help of oxygen, the food, which contains glucose, is broken down inside the cell into carbon dioxide and water. Energy is required for the survival of all living organisms.

Complete answer:
Cellular respiration is a collection of metabolic events that all live cells go through to release energy by turning biochemical energy from foods into adenosine triphosphate-ATP. Cellular respiration is classified into two types based on oxygen demand: aerobic and anaerobic respiration.
Aerobic respiration is a type of cellular respiration that occurs when oxygen is present. All plants and higher creatures, including humans, mammals, and birds, use this sort of respiration. Anaerobic respiration is a type of cellular respiration that occurs without the need of oxygen and is found in all lower species, including bacteria and yeast.

Additional information:
Glycolysis, Krebs' cycle, and the electron transport system are the three phases in the aerobic respiration process. The cytoplasm and mitochondria are the sites of respiration.
During the glycolysis $1$ molecule of the $6$-carbon chemical glucose is broken down into two molecules of $3$-carbon pyruvic acid during glycolysis. This can happen in the presence or absence of oxygen in the cytoplasm. We end up with $2$ pyruvic acid molecules, $2$ ATP molecules, and 2$$$NADH$$ electron transporting molecules in total. The Krebs cycle (also known as the tricarboxylic acid cycle or the citric acid cycle) is a metabolic cycle that occurs in the body. The generated pyruvic acid is transported to the mitochondrial matrix and transformed to acetyl CoA. 2$ molecules of ATP are created after a number of processes. Two chemicals are also produced: nicotinamide adenine dinucleotide $\left( {NADH} \right)$ and flavin adenine dinucleotide $\left( {FADH2} \right)$. They assist in the transport of electrons for the next step.
Oxidative Phosphorylation and the Electron Transport System: It is completely reliant on oxygen. High-energy electrons are passed on through a chain of electron carriers such as $NADH$, resulting in an electron gradient. ATPase converts ADP to ATP by oxidative phosphorylation.

Note:
Energy is required for all cellular activity, and food is the source of energy. Cellular respiration is the process through which cells produce energy in the form of adenosine triphosphate (ATP). It occurs in both eukaryotic and prokaryotic cells. Several oxidation-reduction (redox) reactions transport electrons from organic molecules to other ones during cellular respiration. There are two types of cellular respiration, depending on the oxygen demand: aerobic and anaerobic respiration.