Cellular Respiration Unit III Chapter 9

Flash Cards Due Tomorrow Respiration Next 3 should have (what they do, where they occur, and what they produce) Glycolysis Krebs Cycle Electron Transport Pyruvate Aerobic Respiration Anaerobic Respiration Fermentation

Overview of Cellular Respiration Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen Organisms that respire: animals, fungi, plants (during night hours) Cellular respiration requires a food molecule (such as glucose), oxygen, and it gives off carbon dioxide Because is occurs in the PRESENCE of OXYGEN, cellular respiration is known as AEROBIC respiration

Chemical Formula for Cellular Respiration The chemical formula for cellular respiration is: 6O2 + C6H12O6 → 6 CO2 + 6 H2O + Energy oxygen + glucose → carbon dioxide + water + energy The reactants of cellular respiration are: oxygen (O2) & glucose (C6H12O6) The products of cellular respiration are: carbon dioxide (CO2) and water (H2O)

The 3 main stages of cellular respiration are: Glycolysis Krebs Cycle (Citric Acid Cycle) Electron Transport

Visual Overview of Cellular Respiration Krebs Cycle

Glycolysis The first set of reactions in cellular respiration is glycolysis Glycolysis is the process in which 1 molecule of glucose is broken in half, producing 2 molecules of pyruvic acid Glycolysis occurs in the cytoplasm of the cell Glycolysis produces a total of 4 ATP, but requires 2 ATP in the beginning to get through the membrane of the mitochondria Therefore, the NET ATP YIELD of glycolysis is 2 ATP

The Krebs Cycle In the presence of oxygen, the pyruvic acid produced during glycolysis passes to the Krebs cycle During the Krebs cycle, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions Every time you exhale, you expel the CO2 produced by the Krebs cycle

Electron Transport Following the Krebs cycle, the electrons captured by NADH are passed to the electron transport chain The electron transport chain uses the high-energy electrons from the Krebs cycle to convert ADP to ATP Every time 2 high energy electrons transport down the ETC, their energy is used to transport H+ across the inner membrane of the mitochondria…this creates a + charge on the inside of the membrane and a – charge in the matrix of the mitochondria As a result of this charge difference, H+ ions escape through channel proteins called ATP synthase causing it to rotate Each time it rotates, the enzyme ATP synthase grabs a low energy ADP and attaches a phosphate, forming high-energy ATP

Electron Transport Chain inner membrane space inner membrane Matrix of mitochondria

The Energy Totals The complete breakdown of 1 glucose molecule through cellular respiration results in the production of 36 molecules of ATP Net Energy Gain: 38 ATP Produced - 2 ATP needed to start 36 ATP made!

Respiration in the Absence of Oxygen When oxygen is NOT present, glycolysis is followed by a different pathway called fermentation Because fermentation does not require oxygen, it is said to be anaerobic

Two Main Types of Fermentation Lactic Acid Fermentation: glucose  lactic acid (Ex: Muscles) Alcohol Fermentation: glucose  ethanol (Ex: Yeast, baking, alcohol production) BOTH types of ANAEROBIC RESPIRATION = net gain of 2 ATP