1. Kate Fullerton & Deborah Bakshiyev B9 - Respiration

2. B.9.1 - Compare aerobic and anaerobic respiration of glucose in terms of oxidation/reduction and energy released.

3. Respiration for Chemists Respiration is the controlled breakdown of energy-rich substances into usable forms Ex. Glucose  ATP

4. Glycolysis Glucose (C 6 H 12 O 6 ) and NAD + react to form Pyruvate (C 3 H 3 O 3 - ), NADH, H +, and energy C 6 H 12 O 6 + 2 NAD +  2C 3 H 3 O 3 - + 2NADH + 4H + Half equations: C 6 H 12 O 6  2 C 3 H 3 O 3 - + 6H + + 5e - NAD + + 2H + + 2e -  NADH Reduction: Oxidation: It’s anaerobic!

5. Aerobic Respiration This process requires O 2 from the air O 2 acts as the oxidizing agent It is the ultimate terminal electron acceptor and is reduced to water Final products are CO 2, H 2 O, and energy Pyruvate to CO 2 and H 2 O: C 3 H 3 O 3 - + NADH + 2H + + 3O 2  3CO 2 + 3H 2 O + NAD +

6. Aerobic Respiration Half-Equations: 3O 2 + 12H + + 12e -  6H 2 O C 3 H 3 O 3 - + 3H 2 O  3CO 2 + 9H + + 9e - NADH is also oxidized Reduction: Oxidation:

7. Aerobic Respiration Overall equation (glucose  products): C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O Glucose is oxidized while oxygen is reduced This equation should look familiar… The overall equation is the same as combustion However this process is much more complex with many steps and is controlled by enzymes

8. Anerobic Respiration When no oxygen is present, anerobic respiration (or fermentation) occurs In humans, pyruvate is converted into lactic acid (C 3 H 6 O 3 ) In yeast, pyruvate is converted into ethanol and CO 2

9. Anerobic Respiration Pyruvate  Lactic Acid C 3 H 3 O 3 - + NADH + 2H +  C 3 H 6 O 3 + NAD + Half equations: C 3 H 3 O 3 - + 3H + + 2e -  C 3 H 6 O 3 NADH  NAD + + 2H + + 2e - Lactic acid causes your muscles to feel sore NAD + is used to reduce more pyruvate (cyclic) Reduction: Oxidation:

10. Anerobic Respiration Pyruvate  Ethanol and CO 2 C 3 H 3 O 3 - + NADH + 2H +  C 2 H 5 OH + CO 2 + NAD + Half equations: C 3 H 3 O 3 - + 3H + + 2e -  C 2 H 5 OH + CO 2 NADH  NAD + + 2H + + 2e - NAD + is used to reduce more pyruvate (cyclic) Reduction: Oxidation:

11. Anerobic Respiration Overall equations: Glucose  Lactic Acid C 6 H 12 O 6  2C 3 H 6 O 3 Glucose  Ethanol C 6 H 12 O 6  2C 2 H 5 OH + 2CO 2

12. Energy Release Aerobic respiration releases about 40% of the energy in glucose Anerobic respiration releases about 2% of the energy in glucose *This is because aerobic respiration oxidizes glucose more fully than anaerobic respiration*

13. B.9.2 - Outline the role of copper ions in electron transport and iron ions in oxygen transport

14. Role of Copper in electron transport In the electron transport chain at the end of respiration electrons are passed between proteins in a membrane. – These proteins are called transport carriers Many of these types of electron transport carriers are cytochromes. – They are proteins that contain a non-protein component called a prosthetic group – contain iron and copper – reduced by electrons (in the electron chain) Remember: RIG  reduction is gain of electrons! Later, they are re-oxidized (continue passing along the electron transport chain) – HEME groups are the receptors of the electrons – The iron in the heme group is oxidized from +2 to +3.

15. Diagram of the heme structure of cytochromes

16. Role of Copper in electron transport The terminal electron carrier in the electron transport chain is cytochrome oxidase and contains copper as well as Fe. – copper receives the electron The Cu changes its oxidation state from +1 to +2 as it is oxidized. Binds the electron to O­ 2  forms water

17. Danger of Cyanide (CN - ) CN - binds to the cytochrome oxidase backs up the electron transport chain slows respiration

18. Role of Iron in oxygen transport Hemoglobin – made of 4 polypeptides Each polypeptide has its own HEME group – HEME group = a complex ion! – Each HEME group contains Fe 2+ So, there are 4 Fe 2+ in each hemoglobin molecule In hemoglobin (blood) and myoglobin (muscles) oxygen is transported in a similar heme structure. – Hydrophobic environment  allows oxygen to bind to Fe 2+ without oxidizing it (the Fe stays in the +2 state) So, hemoglobin is described as being oxygenated to oxyhemoglobin rather than oxidized. Quick review: there are 4 HEME groups  that means there are 4 Fe 2+  so, every hemoglobin can bind to 4 O 2 The reversible equation is: – Hb + 4O 2  Hb(O 2 ) 4

19. Danger of Carbon monoxide (CO) CO binds more tightly to Fe 2+ – So you can think that the CO sort of steals the oxygen’s spot with the Fe 2+ Causes lack of oxygen – If CO is not displaced  asphyxiation