1. Cellular Respiration

2. How do Organisms Get Energy?  Photoautotrophs (e.g. plants) Through the sun Through the sun  Chemoautotrophs (e.g. archaebacteria) Make organic compounds without sun’s energy Make organic compounds without sun’s energy  Heterotrophs (e.g. animal, fungi, most protists/bacteria) Through plants Through plants Glucose is the ultimate source of energy Glucose is the ultimate source of energy glucose stores energy in its bonds and cellular respiration is a way to acquire this energy glucose stores energy in its bonds and cellular respiration is a way to acquire this energy

3. Exergonic Redox Reaction C 6 H 12 O 6 + 6O 2  6H 2 O + 6CO 2 + ENERGY C 6 H 12 O 6 + 6O 2  6H 2 O + 6CO 2 + ENERGY as the bonds WITHIN the glucose molecule are broken down, energy is released as the bonds WITHIN the glucose molecule are broken down, energy is released To summarize even more, glucose stores energy in its bonds and cellular respiration is a way to acquire this energy! To summarize even more, glucose stores energy in its bonds and cellular respiration is a way to acquire this energy! These bonds are broken through EXERGONIC OXIDATION-REDUCTION reaction These bonds are broken through EXERGONIC OXIDATION-REDUCTION reaction C 6 H 12 O 6 oxidized to 6CO 2, and 6O 2 reduced to 6H 2 O C 6 H 12 O 6 oxidized to 6CO 2, and 6O 2 reduced to 6H 2 O  each carbon in C 6 H 12 O 6 is converted to CO 2  each hydrogen in C 6 H 12 O 6 is converted to ½H 2 O

4. Combustion of Glucose In test tube In cellular respiration In cellular respiration energy is released from combustion of glucose. 34% of this energy goes to ATP; 66% goes to heat

5. Aerobic vs Anaerobic Respiration C 6 H 12 O 6 + 6O 2  6H 2 O + 6CO 2 + ENERGY C 6 H 12 O 6 + 6O 2  6H 2 O + 6CO 2 + ENERGY In the above equation oxygen is the electron acceptor in the oxidation of glucose In the above equation oxygen is the electron acceptor in the oxidation of glucose Most organisms are obligate aerobes – they require oxygen and cannot survive without it Most organisms are obligate aerobes – they require oxygen and cannot survive without it Obligate anaerobes (some species of bacteria) use other molecules as the final electron acceptor and must live in environments that has no oxygen Obligate anaerobes (some species of bacteria) use other molecules as the final electron acceptor and must live in environments that has no oxygen Facultative anaerobes can tolerate aerobic and anaerobic conditions Facultative anaerobes can tolerate aerobic and anaerobic conditions

6. Mitochondria Smooth Highly folded Folds of the inner membrane Protein-rich liquid Fluid-filled intermembrane space

7. Energy Transfer Terminology Substrate-level Phosphorylation: ATP forms directly in an enzyme-catalyzed reaction. Oxidative Phosphorylation: ATP forms indirectly through a series of enzyme- catalyzed redox reactions involving oxygen as the final electron acceptor. Done mainly through compounds called energy carriers Done mainly through compounds called energy carriers These reactions harness energy, which is eventually transferred to ATP These reactions harness energy, which is eventually transferred to ATP

8. Energy Carriers NAD + and FAD + are low energy, oxidized coenzymes that act as electron acceptors. When an electron(s) are added to these molecules, they become reduced to NADH and FADH 2. In this case, reducing a molecule gives it more energy.

9. Aerobic Respiration: Overview Occurs in Four Distinct Stages: 1. Glycolysis: 10-step process in the cytoplasm. 2. Pyruvate Oxidation: 1-step process in the mitochondrial matrix. 3. Krebs Cycle: 8-step cyclical process in the mitochondrial matrix. 4. Electron Transport Chain : Multi-step process in the inner mitochondrial membrane.

12. Glycolysis - Overview Takes Place in the Cytoplasm Enzymes break down glucose (6 carbons) into two smaller molecules of pyruvate (3 carbons), releasing ATP Does not require oxygen

15. Glycolysis – Key parts of process 2 ATPs are used in steps 1 & 3 to prime glucose for splitting. F 1,6-BP splits into DHAP and G3P. DHAP converts to G3P. 2 NADH are formed in step 6. 2 ATP are formed by substrate-level phosphorylation in both steps 7 and 10. 2 pyruvates are produced in step 10.

16. Glycolysis Energy Yield & Products: 4 ATP produced – 2 ATP used = 2 net ATP 2 NADH 2 pyruvates Further processing in aerobic cellular respiration (if oxygen is available)

17. Energy Created Glycolysis – Energy Created Creates 2 molecules of ATP (2 x 31 kJ/mol) Creates 2 molecules of ATP (2 x 31 kJ/mol) Yields 62 kJ of energy, from a possible 2870 kJ/glucose (only a 2.2% energy conversion) Yields 62 kJ of energy, from a possible 2870 kJ/glucose (only a 2.2% energy conversion) Most energy is still trapped in pyruvate and the 2 NADH molecules, but some lost as heat Most energy is still trapped in pyruvate and the 2 NADH molecules, but some lost as heat Earliest cells in Earth’s history thought to have used this method of energy metabolism since oxygen is not required and enough energy is produced to sustain life in unicellular organisms Earliest cells in Earth’s history thought to have used this method of energy metabolism since oxygen is not required and enough energy is produced to sustain life in unicellular organisms simple organisms today use glycolysis for energy simple organisms today use glycolysis for energy In multicellular organisms glycolysis takes place first in the cytoplasm, and then more processes in the mitochondria to yield more energy In multicellular organisms glycolysis takes place first in the cytoplasm, and then more processes in the mitochondria to yield more energy

18. Pyruvate Oxidation (if oxygen is present…) The following occurs for each pyruvate: 1. CO 2 removed. 2. NAD + reduced to NADH and the 2-carbon compound becomes acetic acid. 3. Coenzyme A (CoA) attaches to acetic acid to form acetyl-CoA.

19. Pyruvate Oxidation

20. Energy Yield & Products: 2 NADH 2 acetyl-CoA 2 CO 2 (released as waste)

21. Acetyl-CoA CoA comes from vitamin B 5 CoA comes from vitamin B 5 Proteins, lipids, and carbohydrates are catabolized to ‘acetyl-CoA’ Proteins, lipids, and carbohydrates are catabolized to ‘acetyl-CoA’ It can be used to make fat or ATP It can be used to make fat or ATP [ATP] determines what pathway this molecule takes [ATP] determines what pathway this molecule takes If O 2 is present, ‘acetyl CoA’ moves to the Kreb’s Cycle (aerobic respiration) If O 2 is present, ‘acetyl CoA’ moves to the Kreb’s Cycle (aerobic respiration) If O 2 is NOT present, ‘acetyl CoA’ becomes ‘lactate’ (anaerobic respiration / fermentation) If O 2 is NOT present, ‘acetyl CoA’ becomes ‘lactate’ (anaerobic respiration / fermentation)