Cellular Respiration Chapter 5 Section 3

Cellular Energy All of the energy you use comes from the food you eat Before you can use that energy, the food is broken down and the energy is stored as ATP. The transfer of the energy in organic compounds (particularly glucose) to ATP is called RESPIRATION. Aerobic vs. anaerobic

The Stages of Respiration Balanced chemical Equation for Cellular Respiration (aerobic)

Stages of Respiration 1. Glucose is broken down to pyruvate during glycolysis

Glycolysis 2 Glycolysis-the first stage of cellular respiration in which glucose is broken down in the cytoplasm. Glycolysis is an enzyme-assisted anaerobic process that breaks down 1 six-carbon sugar(glucose) into 2 three carbon pyruvate molecules Net Yield vs. Net Gain?

Stages of Respiration 1. Glucose is broken down to pyruvate during glycolysis 2. Krebs Cycle

The Krebs Cycle Named for Hans Krebs, who first described the cycle in 1937. When O₂ is present, the pyruvate produced by glycolysis enters the mitochondrion and is converted to a 2-carbon compound Acetyl CoA. Also called the Citric Acid Cycle

Krebs Cycle Net Gain for the Krebs Cycle is 2 ATP’s. Remember that Glycolysis produces 2 pyruvate molecules, thus providing 2 rounds of the Krebs Cycle.

Electron Transport Chain In eukaryotic organisms, the ETC is located in the inner membranes of the mitochondria. Hydrogen ions accumulate in the outer compartment producing a concentration gradient across the inner membrane. H+ ions diffuse back into the inner compartment through a carrier protein that adds a phosphate group to ADP→ATP.

Electron Transport Chain

Stages of Respiration

Respiration in the Absence of O₂ Fermentation-The recycling of NAD+ (nicotinamide adenine dinucleotide phosphate-oxidase ion) using an organic hydrogen acceptor. Two Important types: 1. Lactic Acid Fermentation 2. Alcoholic Fermentation

Lactic Acid Fermentation Three Carbon Pyruvate molecule (glycolysis product) is converted to 3-carbon lactate. Lactate is the ion of an organic acid called lactic acid. Allows glycolysis to continue in the absence of O₂ During vigorous exercise, pyruvate in muscles is converted to lactate when muscles must operate without enough O₂, causing soreness. Blood removes most lactate

Lactic Acid Fermentation

Alcoholic Fermentation Used by some bacteria, fungi and prokaryotes. Occurs in a two-step process: The three carbon pyruvate is broken down into a , a two-carbon compound, releasing carbon dioxide. Electrons are transferred from a molecule of NADH to the two-carbon compound, producing ethyl alcohol. As in lactic acid fermentation, the NAD+ is recycled and glycolysis continues.

Alcoholic Fermentation

In the Presence of O₂…

Without the Presence of O₂ Alcohol Fermentation Lactic Acid Fermentation