Overview of Cellular Respiration -Organisms obtain energy (ATP) in a process called cellular respiration. -The equation for cellular respiration is the opposite of the equation for photosynthesis. Memorize this equation

Cellular respiration can be broken into three major parts: Glycolysis The Kreb’s Cycle The electron transport chain (ETC)

1. Glycolysis -In a series of enzymatically catalyzed steps, glucose is broken down into pyruvate in the cytoplasm through the process of glycolysis. -In addition to pyruvate, two molecules of ATP and two molecules of NADH (electron carriers) are formed for each molecule of glucose that is broken down. *If no oxygen is present – the process stops here. Only 2 ATP have been made. This is called anaerobic respiration.

-Two molecules of pyruvate are the products of the glucose being broken down. They move on to the Kreb’s cycle inside the mitochondria.

A.K.A. The Citric Acid Cycle 2. Krebs Cycle A.K.A. The Citric Acid Cycle -After glycolysis, most of the energy from the glucose is still contained in the pyruvate. -The Kreb’s Cycle is a series of reactions in which pyruvate is broken down into carbon dioxide. It occurs in the matrix of the mitochondria. -In the process of breaking down the pyruvate several electron carriers pick up high energy electrons for the final phase of cellular respiration. -The net yield from the Krebs cycle is six CO2 (waste) molecules, two ATP, eight NADH, and two FADH2 (electron carriers).

3. Electron Transport Chain -The final step of cellular respiration involves using the electrons that have been stripped (by the electron carriers – NADH and FADH2)from the glucose to power hydrogen ion pumps. These hydrogen ions then provide the energy to form the ATP (32 ATP – WOW!). The electron transport chain also occurs within the mitochondria. A total of 36 ATP can be made per glucose.

Building a concentration gradient. More H+ outside and less inside. (requires active transport). These H+ repel each other. This repelling provides the energy to add P to ADP and make ATP.

What types of organisms perform cellular respiration? Almost all living organisms!!! A few types of organisms are capable of just anaerobic respiration. Also, chemotrophs (very rare) can use other elements such as sulfur, iron or hydrogen for their energy. Most of these are in the domain archea