Cellular Respiration → breaking down food (chemical energy) to get ATP

1. CH 9 – Cellular Respiration Cellular Respiration → breaking down food (chemical energy) to get ATP

2. mitochondria • Powerhouse of the cell! • The organelle responsible • for cellular respiration • The Krebs Cycle and ETC • take place here  ATP is • produced here! • It is a double membrane • with the inner membrane • highly folded (to increase • the surface area and • make the mitochondria • more efficient). Intermembrane Space

3. Equation – C6H12O6  +  6O2  →  6CO2  +  6 H2O  +  36 or 38 ATP Cellular Respiration – Background info • When food is broken down, energy is released gradually and stored in ATP. • Respiration is done by BOTH plants and animals

4. General overview – Cellular Respiration • Glycolysis: • In the cytosol • Anaerobic • Turns glucose to 2 pyruvate  net gain of 2 ATP and 2 NADH • Krebs: • In the mitochondrial matrix • Makes little ATP, NADH, and FADH2 (electron taxis) • Passes e- to ETC ETC→ uses chemiosmosis to make LOTS of ATP

5. Glycolysis Main Goal of Glycolysis is to turn glucose into two pyruvate: - Series of 10 steps - Produces a net gain of 2 ATP and 2 NADH (e- carriers) - From here it can go to the Krebs cycle (aerobic respiration) or to Fermentation (anaerobic) - Glycolysis is anaerobic - Occurs in the cytosol Overall: Glucose → 2 Pyruvate; net gain 2 ATP and 2 NADH

6. Intermediate step Pyruvate (made in the cytosol via glycolysis) diffuses into the mitochondria. As it diffuses is, it loses a carbon (goes from 3C to 2C) when it produces one molecule of CO2. This new 2C molecule is acetyl CoA. Acetyl CoA is what goes into the Krebs cycle.

7. Krebs/ citric acid cycle Main Function of the Krebs→ to make electron carriers (NADH and FADH2) to send to the ETC Series of 8 steps; Occurs in the mitochondrial matrix So…1 glucose produces: 2 ATP 6 NADH 2 FADH2 (remember: 1 glucose = 2 pyruvates) Electron Carriers Acetyl CoA (2C) enters the Krebs and combines with another molecule (4C) to form citric acid (hence citric acid cycle)

8. Krebs → Makes 1 ATP, 3 NADH, and 1 FADH2 per turn You do NOT need to memorize this!

9. Electron transport chain (ETC) Occurs on the inner membrane of the mitochondria; Energy from NADH and FADH2 power ATP synthesis The ETC is a series of proteins throughout the membrane; the electrons lose energy every time they get passed down the chain OXYGEN IS THE FINAL ELECTRON ACCEPTOR!!! → oxygen combines with the electrons and H+ to make WATER

10. Main Goal of the ETC → it’s a stepwise free energy drop from food to oxygen; it creates a proton gradient that powers chemiosmosis to create ATP via ATP Synthase The ETC uses energy from the electrons and pumps the protons OUT of the matrix into the intermembrane space; it then diffuses back in via ATP synthase.

11. Final e- acceptor after they go down the ETC is OXYGEN (from the atmosphere) …it combines with e- and H+ to make WATER • NADH and FADH2 drop off e- to the ETC • -As the e- get passed down the chain, they lose energy; that energy is used to pump H+ OUT of the matrix into the intermembrane space • -This creates a concentration gradient • -The protons then diffuse back INTO the matrix via the ATP synthase (chemiosmosis); this creates ATP • -Makes a TON of ATP!!!

12. ATP Summary → Glycolysis – 2 Krebs – 2 ETC – 32/34 Cellular Respiration overview

13. Cellular respiration vs. fermentation Oxygen Present → Aerobic Respiration (efficient!) Oxygen NOT Present → Fermentation (not efficient) Respiration = 66% efficient Fermentation = 3.5% efficient

14. If there is no oxygen present (anaerobic) the pyruvate (from glycolysis) goes to fermentation The main goal of fermentation is to make NAD+ to put back into glycolysis; it makes NO ATP on its own (it just keeps glycolysis going so that it can make 2 ATP at a time) Occurs in cytosol 2 types of fermentation: alcohol and lactic acid Fermentation

15. Alcoholic Fermentation • Pyruvate is turned into ethanol • CO2 is released (bubbles!) • Done by yeast for brewing Remember: Goal is to produce NAD+ to send back to glycolysis so it can keep going and produce more ATP 3C Pyruvate → 2C Ethanol

16. - Pyruvate is turned into Lactate (or lactic acid) • Lactate is eventually carried away by the blood to the liver where it gets converted back into pyruvate • Example: Muscle Cells!! • The lactic acid is what makes your muscles sore after lifting or intensive exercise • No CO2 is released Lactic acid fermentation Remember: Goal is to produce NAD+ to send back to glycolysis so it can keep going and produce more ATP 3C Pyruvate → 3C Lactate

17. Lactic acid vs. alcohol fermentation Both start with pyruvate from glycolysis Alcohol makes ethanol and gives off CO2 Lactic acid makes Lactic acid and does NOT give off CO2 Both create NAD+ to be sent back to glycolysis Neither make any ATP on their own

18. Fermentation - Overview Obligate Aerobes → needs oxygen; can do respiration only Obligate Anaerobes → can’t have oxygen; fermentation only Facultative Anaerobes → can live with or without oxygen; prefer oxygen b/c more efficient Respiration is 19 times more efficient than fermentation (38 ATP vs. 2 ATP)