EVERYDAY SCIENCE

Detailed explanation-1: -The first step of this pathway begins with the decarboxylation of pyruvate to the Krebs cycle starting molecule, acetyl-CoA.

Detailed explanation-2: -The citric acid cycle is called a cycle because the starting molecule, oxaloacetate (which has 4 carbons), is regenerated at the end of the cycle.

Detailed explanation-3: -The Krebs cycle uses the two molecules of pyruvic acid formed in glycolysis and yields high-energy molecules of NADH and flavin adenine dinucleotide (FADH2), as well as some ATP. The Krebs cycle occurs in the mitochondrion of a cell (see Figure 6-1).

Detailed explanation-4: -Glycolysis, the first step of cellular respiration, occurs in the cytoplasm of your cells. During this process, a glucose molecule is broken down into two molecules of pyruvate (pyruvic acid).

Detailed explanation-5: -Pyruvic acid supplies energy to living cells through the citric acid cycle (also known as the Krebs cycle ) when oxygen is present (aerobic respiration); it ferments to produce lactic acid when oxygen is lacking ( fermentation ). Pyruvate is the output of the anaerobic metabolism of glucose known as glycolysis.