Cellular Respiration

1. Cellular Respiration Energy for life’s activities

2. Overview of Cellular Respiration • The life processes of ALL organisms require energy. • The potential energy held in the bonds of food molecules CANNOT be used directly by the cell. • Energy from food must be converted to the ONLY energy source that cells can use … ATP!

3. Review of ATP • Adenosine Triphosphate • Result of the bonding of a free phosphate w/free ADP molecule • The bond between the phosphates is where the actual energy is stored

4. Review of ATP, cont. • When the bond between the phosphates is broken, energy is released

5. Cellular Respiration Defined • Respiration is the process by which the energy in the bonds of nutrients are used to synthesize ATP. • Respiration occurs continuously in all cells of all organisms. • The energy needed to synthesize ATP comes from an organism’s food

6. Summary of Cell Respiration ATP ATP energy (in) energy (out) energy (out) cellular respiration cellular respiration cell activities cell activities ADP + P The whole process is an enzyme controlled reaction.

7. Aerobic Respiration • Aerobic Respiration – respiration with oxygen C6H12O6 + 6O2 6CO2 + 6H2O energy (to make ATP)

8. Aerobic Respiration, cont. • Happens in 2 stages: • Stage 1 – Glycolysis • glyco – glucose lysis – splitting • In glycolysis, a glucose molecule is broken into 2 pyruvic acids • This requires the input of 2 ATP molecules as activation energy

9. glucose series of enzyme controlled reactions energy released to make small quantity of ATP (2 molecules) pyruvic acid Glycolysis does not require oxygen

10. Aerobic Respiration, cont. • Stage 2 – Breakdown of pyruvic acid • The pyruvic acid made in glycolysis still contains a lot of energy • It can only be broken down to release the rest of the energy in the presence of oxygen

11. pyruvic acid energy released to make large quantity of ATP (34 molecules) series of enzyme controlled reactions carbon dioxide + water

12. Summary of ATP production • Stages 1 and 2 release all the chemical energy in one molecule of glucose to make a total of 36 molecules that can be used by the organism • There is actually enough energy in a glucose molecule to make ~90 ATP, but the rest is lost as heat

13. ATP production – summary glucose 2 ADP + 2 P = 2 ATP pyruvic acid 34 ADP + 34 P = 34 ATP ~56 ATP (heat) carbon dioxide + water

14. The Mitochondrion

15. The Role of the Mitochondrion • In order for the cell to capture as much energy as it possibly can from it’s food, a series of controlled reactions requiring the input of oxygen is necessary • These reactions are directed by the mitochondrion

16. The Role of the Mitochondrion, cont. • Glycolysis occurs in the cytosol (cytoplasm) of the cell • The aerobic reactions occur in the mitochondria of the cell and are divided into 2 stages

17. The Role of the Mitochondrion, cont. • Stage 1 – The Krebs (Citric Acid) Cycle • Discovered by Hans Krebs in 1937 • Pyruvic acid is broken down into CO2 in a series of energy-extracting reactions • The first compound formed in this series of reactions is citric acid • This is the stage that is the source of all the CO2 that you exhale

18. The Krebs Cycle occurs in the matrix of the mitochondrion Krebs Cycle

19. The Role of the Mitochondrion, cont. • Stage 2 – The Electron Transport Chain • The Krebs Cycle generates many high-energy hydrogen atoms • Oxygen is added as an electron carrier at this stage • When the oxygen binds with the hydrogen, energy is released to form ATP and water is made

20. The electron transport chain occurs in the cristae of the mitochondrion. Electron Transport Chain

22. Anaerobic Respiration • Also called fermentation • Happens in low/no oxygen conditions • 1 Glucose only partially broken down to form waste products and 2 ATP

23. Anaerobic Pathways • Pathway 1- Lactic Acid Fermentation • Glucose  2 lactic acid + 2 ATP • Happens in muscle cells when they run out of oxygen • Happens in bacteria that make yogurt, cheese, dill pickles

24. glucose glycolysis still happens as it does not require oxygen 2 ADP + 2 P 2 ATP pyruvic acid in absence of oxygen pyruvic acid is turned into lactic acid. lactic acid

25. Anaerobic Pathways, cont. • A build up of lactic acid produces muscle fatigue • This makes the muscles ache and contract with less power • A recovery period is needed; during this time more O2 is taken in which converts lactic acid back into pyruvic acid • The volume of O2 needed is called oxygen debt

26. Anaerobic Pathways, cont. • Pathway 2 – Alcoholic Fermentation • Glucose  2 ethanol + 2 CO2 + 2 ATP •  process in which sugars are converted into alcohol and carbon dioxide by the action of various yeasts, molds, or bacteria

27. glucose pyruvic acid 2 ADP + 2 P 2 ATP glycolysis still happens, producing 2 ATP molecules This time in absence of oxygen, pyruvic acid is turned into carbon dioxide and ethanol This is irreversible ethanol + carbon dioxide

28. Comparing Aerobic & Anaerobic Cellular Respiration Pathways

29. Adaptations for Respiration • Bacteria, protists & fungi • Respiratory gases are exchanged by diffusion • Plants • Respiratory gases are exchanged through leaves, stems, and roots • Moves in and out of cells by diffusion but leaves and stems also have openings to the environment (stomata)

30. Adaptations for Respiration in Animals • Techniques vary: • Simple diffusion across cell membranes • Diffusion across moist skin into a circulatory system • Openings to the environment that can be flapped open and closed with a circulatory system to transport gases • Specialized respiratory structures (e.g. lungs) to speed exchange of respiratory gases