1. Chapter 8 Cellular respiration

2. Why Energy All active organisms use energy Carbon dioxide and water are both metabolic by-products produced by living cells

3. How do cells make ATP? ATP is the prime energy carrying molecule for all cells Aerobic respiration (with oxygen) is the main pathway for releasing energy from carbohydrates All energy releasing pathways begin with glycolysis –Glucose is split into two pyruvate molecules –Glycolysis happens in the cytoplasm without the use of oxygen

4. Aerobic Respiration Yields 36 ATP from every glucose; fermentation yields only 2 C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O 3 series of reactions are needed for aerobic respiration –Glycolysis the breakdown of glucose to pyruvate, small amounts of ATP are made –Krebs cycle- degrades pyruvate to carbon dioxide, water, ATP, H+, and electrons –Electron transfer phosphorylation- processes H+ and electrons to generate high yields of ATP, oxygen is the final electron acceptor

5. Aerobic respiration

6. Glycolysis Enzymes in cytoplasm catalyze several steps in the breakdown of glucose –Glucose is immediately phosphorylated and is split to form two molecules of PGAL –Enzymes remove H+ from PGAL and transfer them to NAD+ which is changed to NADH –4 ATP are produced End products are 2 pyruvates, 2ATP, 2 NADH

7. Glycolysis

8. Krebs Cycle Pyruvate enters the mitochondria and is converted to AcetylCoEnzyme-A which joins oxaloacetate that is already present During each turn of the cycle, 3 carbons enter as pyruvate and three leave as carbon dioxide H+ and electrons are transferred to NAD+ and FAD 2 molecules of ATP are produced Most of the molecules are recycled CO 2 is produced

9. Krebs cycle

10. Third stage NADH and FADH2 give electrons to transfer systems in the mitochondria Energy from electrons is released and is used to pump hydrogen out of the mitochondria The flow of hydrogen ions through ATP synthase channels joins ADP + P to make ATP Oxygen joins with the “spent” H+ to yield water

11. Electron transport chain

12. Summary of energy harvest Electron transfer yields 34 ATP Glycolysis yields 2 ATP Krebs yields 2 ATP For every NADH=3ATP, FADH2=2ATP NADH from cytoplasm cannot enter mitochondria and must transfer electrons In most cells the electrons are transferred to FAD and yield 2 ATP In liver, heart, and kidney cells NAD+ accepts the electrons and yields 3 more ATP for a total of 38

13. Anaerobic respiration or fermentation

14. Fermentation Anaerobic respiration- happens without oxygen- pyruvate is metabolized to produce molecules other than ACoA Energy yields are only 2 ATP- so is limited to single-celled orgs. Or multicelled for limited times Begins with glycolysis- just like aerobic

15. Lactic Acid fermentation Certain bacteria (like those in milk) and muscle cells have enzymes capable of converting pyruvate to lactate No additional ATP is made, but NAD+ is regenerated Lactic acid is a byproduct

16. Alcoholic fermentation Begins with glucose degradation to pyruvate Enzymes convert pyruvate to acetaldehyde, which accepts electrons from NADH to become alcohol Yeasts are valuable in the baking industry By-products are CO2 and alcohol

17. Anaerobic electron transfer Some bacteria are able to strip electrons from organic compounds and send them through special electron transfer to produce ATP Examples include those that can reduce sulfate to hydrogen sulfide and those that can convert nitrate to nitrite. These are the bacteria that make swamps smell like rotten eggs

18. Alternative energy sources Excess carbohydrates are stored as glycogen in the liver and muscle for future use Free glucose is used until it runs low, then glycogen is used Excess fats are stored in cells of adipose tissue Fats are digested into glycerol which enters glycolysis and fatty acids that enter Krebs cycle Fats have more carbon and are degraded slowly Amino acids in proteins are released during digestion. After the amino group is broken down, the amino acid remnant enters Krebs cycle

19. Photosynthesis and Respiration The two reactions are essentially the mirror images of each other. The products of one are the reactants in the other Life is not a mysterious force, but a series of chemical reactions under tight control