Cellular Respiration Basics and Glycolysis
Cellular respiration happens primarily in mitochondria, the powerhouse organelles with an inner membrane surrounding a matrix. This process uses specific energy carriers—ATP, NADH, and FADH₂—to transfer and store energy throughout the process.
The journey begins with glycolysis, which occurs in the cytoplasm outside the mitochondria. During this first step, 2 ATP molecules are used to split glucose (a 6-carbon molecule) into two 3-carbon pyruvate molecules. This process actually generates 4 ATP and 2 NADH, giving a net gain of 2 ATP molecules.
The Krebs Cycle (also called the citric acid cycle) follows glycolysis and takes place in the mitochondrial matrix. Each pyruvate molecule is broken down into a 2-carbon fragment, releasing CO₂ and creating NADH. The 2-carbon fragment enters the cycle after joining with a molecule called Co-A. Through a series of reactions, more NADH, some ATP, and more CO₂ are produced.
Energy Insight: Every time chemical bonds break during cellular respiration, energy is released. This energy isn't wasted—it's captured in energy-carrying molecules like ATP and NADH that your cells can use later!
