Overview of Energy-Releasing Pathways AP Biology Fall 2010

 Heterotrophs: get energy by eating plants and one another  Autotrophs: get energy from the sun  ATP is the prime energy carrier for all cells, both autotrophic and heterotrophic

 Anaerobic: reactions that do not use free oxygen  Anaerobic respiration and fermentation can release small quantities of energy without the use of oxygen  First energy-releasing metabolic pathways  Skeletal muscles use fermentation

 Aerobic: reactions that use free oxygen  Aerobic respiration is the main energy-releasing pathway leading to ATP formation in eukaryotes  Occurs in mitochondria

 Every cell begins its energy-releasing pathways with glycolysis, which occurs in the cytoplasm and produces two molecules of pyruvate  Fermentation produces a net yield of two ATPs  Aerobic respiration yields 36 ATPs

 Aerobic respiration gets the most ATP for each glucose molecule  “The most bang for your buck”  The aerobic route is summarized:  C 6 H 12 O 6 + O 2  CO 2 + H 2 O

 Three series of reactions are required for aerobic respiration 1. Glycolysis: the breakdown of glucose to pyruvate; small amounts of ATP are generated 2. Krebs cycle: degrades pyruvate to carbon dioxide and water, ATP is produced, and NAD and FAD accept H + ions and electrons to be carried to the electron transfer chain

3. Electron transfer phosphorylation: processes the H + ions and electrons to generate high yields of ATP; oxygen is the final electron acceptor

 Coenzymes:  NAD + (nicotinamide adenine dinucleotide)  FAD (flavin adenine dinucleotide)  Both accept electrons and hydrogen derived from intermediates that form during glucose breakdown  When two coenzymes are carrying electrons and hydrogen, in reduced form  NADH and FADH 2

1. What are NAD+ and FAD? 2. What is the formula for aerobic respiration? 3. What are the three stages of aerobic respiration? 4. How much energy does fermentation and anaerobic respiration produce? Do they use oxygen?

1. They are coenzymes that both accept electrons and hydrogen derived from intermediates that form during glucose breakdown. 2. The formula for aerobic respiration is: C 6 H 12 O 6 + O 2  CO 2 + H 2 O 3. The three stages of aerobic respiration are: Glycolysis, Krebs cycle, electron transfer phosphorlation. 4. Fermentation and anaerobic respiration produces small amounts of energy and does not require oxygen.