Unit 5 Cell Energy 5 6 KrebsCitric Acid

Unit 5: Cell Energy 5. 6 Krebs/Citric Acid Cycle

In the presence of oxygen, pyruvic acid produced in glycolysis passes to the second stage of cellular respiration

Krebs/Citric Acid Cycle • Second set of reactions in cellular respiration in which pyruvic acid is broken down into carbon dioxide Because citric acid is the first compound formed in this series of reactions, is it also known as the citric acid cycle.

Summary • Takes place in the mitochondrial matrix

Summary • Aerobic

Summary • Starts with pyruvic acid from glycolysis 1 Carbon from pyruvic acid becomes part of carbon dioxide and is eventually released into the air The other 2 carbons form acetic acid, which bonds to coenzyme A to produce acetyl Co. A. Acetyl Co. A reacts to form citric acid (6 carbon molecule)

Pyruvic Acid (3 Carbon) Bonds with Coenzyme A to create Acetyl Co. A (2 Carbon) Becomes part of CO 2 and is eventually released into the air Reacts with oxaloacetate to form citric acid (6 Carbon) Krebs Cycle!

Summary • As the cycle continues, citric acid is broken down (to a 4 carbon molecule) Carbon dioxide and energy are released The molecule needed to start the reactions of the cycle is remade with every turn (oxaloacetate)

ATP

Summary • Each starting molecule of glucose results in two complete turns of the Krebs Cycle Glycolysis produces 2 molecules of pyruvic acid from 1 molecule of glucose, allowing the cycle to run twice.

Production One turn through the cycle produces: Two turns through the cycle produces: • 3 NADH • 6 NADH • 1 FADH 2 • 2 FADH 2 • 1 ATP • 2 CO 2 • 4 CO 2

ATP