Biology 12 - respiration

Cellular respiration Provides energy for the cell Occurs in all cells Net equation: glucose + oxygen  carbon dioxide + water + energy (ATP) Occurs as a series of reactions, involving many different enzymes Involves anaerobic and aerobic reactions

ATP and ADP Act as chemical batteries Carry and release small amounts of energy ATP adenosine adenosine phosphate ADP energy

Anaerobic respiration Occurs in the cytoplasm Does not need oxygen Involves 2 processes – glycolysis and fermentation

Glycolysis Glucose is broken down into 2 pyruvate (pyruvic acid) molecules Reactions use 2 ATP Reactions make 4 ATP Net ATP = 2/glucose molecule

Fermentation In animals: Pyruvate is converted to lactic acid In plants and fungi: Pyruvate is converted to ethanol and carbon dioxide

Aerobic respiration Occurs in the mitochondrion Needs oxygen Involves Transition reaction, Krebs cycle and Electron transport chain Involves many reactions and enzymes Produces 36 ATP Waste products are carbon dioxide and water

Structure of mitochondrion

Transition reaction Pyruvate attaches to Coenzyme A to form Acetyl Coenzyme A Acetyl Coenzyme A enters mitochondrion and releases the pyruvate into the Krebs cycle Coenzyme A can also pick up fatty acids and take them into the Krebs cycle

Transition reaction

Krebs cycle Occurs in the matrix of the mitochondrion A cycle of reactions generates ATP and hydrogen ions (carried by NAD and FAD carriers to electron transport chain) Waste product is carbon dioxide Produces 2 ATP/glucose molecule

Krebs cycle

Carrier proteins Carry hydrogen ions to electron transport chains NAD  NADH + H+ FAD  FADH2 + H+

Electron transport chain Found in the cristae (inner membranes) of the mitochondrion ATP is generated as hydrogen ions are passed down the chain Oxygen is used up Waste product is water Produces 34 ATP/glucose molecule

Electron transport chain

Summary of reactions

Comparison of aerobic and anaerobic respiration Site it occurs cytoplasm mitochondrion Need for oxygen no yes Waste products Animals – lactic acid Plants – carbon dioxide and alcohol Carbon dioxide and water Amount of ATP 2/glucose molecule 36 – 38/glucose molecule Reactions involved Glycolysis Fermentation Transition reaction Krebs cycle Electron transport chain