Cellular Respiration

1. Cellular Respiration Topic 3.7 and 3.8

2. Assessment Statements: SL 3.7.1 Define cell respiration. 3.7.2 State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysisinto pyruvate, with a small yield of ATP. 3.7.3 Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP. 3.7.4 Explain that, during aerobiccell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.

3. Cellular Respiration: Standard level How does the process of cellular respiration yield ATP (chemical energy) from food? What do you already know about cellular respiration? What organelle in the cell is the “powerhouse” that makes energy for the cell?

4. What is ATP? Energy ‘currency’ used by all cells Adenosine triphosphate Organic molecule containing high-energy phosphate bonds

5. Chemical Structure of ATP Adenine Base 3 Phosphates Ribose Sugar

6. How Do We Get Energy From ATP? By breaking the high- energy bonds between the last two phosphates in ATP ATP hydrolase (ATP’ase) catalyses the breakdown of ATP into ADP + Pi

7. Each day, you hydrolyse 1025 ATP molecules ATP-ase ATP Synthetase

8. HYDROLYSIS (Adding H2O) H2O

9. How is ATP re-made? Substrate-level phosphorylation (using enzymes: in the cytoplasm of the cell and the matrix of the mitochondrion) Chemiosmosis (in the mitochondria, using ATP synthase)

10. Substrate level phosphorylation and chemiosmosis

11. Definition of cellular respiration Controlled release of energy from organic compounds to produce ATP • Cells break down organic compounds by SLOW oxidation • Chemical energy is stored in covalent bonds • By releasing energy in a controlled way, it can be trapped in the ‘useful’ form of ATP

14. Cellular Respiration Breakdown of one glucose results in 36 to 38 ATP molecules • Metabolic Pathway that breaks down carbohydrates • Process is exergonic as high-energy glucose is broken into CO2 and H2O • Process is also catabolic because glucose breaks into smaller molecules

15. Equations for aerobic respiration All of these are fine!....

16. Equation for Cellular Respiration C6H12O6 + 6O2 YIELDS 6CO2 + 6H20 + e- + 36-38ATP + heat

17. Stages of Cellular Respiration • Glycolysis ALWAYS OCCURS • Anaerobic pathways if no oxygen available (Lactic acid and Ethanolfermentation) • Aerobic pathways if oxygen available (Link reaction, Krebs cycle, electron transport chain)

19. Where Does Cellular Respiration Take Place? glycolysis occurs in the cytoplasm Krebs Cycle & ETC Takeplace in the mitochondria

21. Glycolysis: Always the initial stage of respiration • Location: cytoplasm • Substrate: glucose • Requires input of 2 ATP • Products: pyruvate, (NADH), 4 ATP Glycolysis is an anaerobic process: no oxygen required the movie...

22. Glycolysis

23. If no oxygen is available, glycolysis (anaerobic) is followed by fermentation (anaerobic)

24. Why fermentation? In the absence of oxygen, glycolysis soon stops unless there is an alternative acceptor for the electrons produced from the glycolytic pathway

25. Fermentation 1. Alcoholic fermentation Pyruvate is converted into ethanol plus carbon dioxide and NAD+ • Lactate fermentation Pyruvate is converted into lactate and NAD+

26. Alcoholic fermentation in yeast

27. Alcoholic fermentation in yeast • Pyruvate is produced from glycolysis • 3-carbon pyruvate is converted to 2-carbon ethanol and carbon dioxide • Generation of carbon dioxide helps bread products to rise • Yeast is used to produce ethanol

28. Lactate fermentation in mammals Lactate is a 3-carbon molecule NAD+ is regenerated to allow glycolysis to continue

29. Aerobic respiration • Takes place in the mitochondria of eukaryotic cells • Substrate: pyruvate • Produces LOTS of ATP (28 – 38 ATP): 90% of total ATP from respiration • Also produces carbon dioxide, water and heat • Oxygen is the final electron acceptor

30. Aerobic respiration: the most efficient pathway for ATP generation

31. Aerobic respiration • 2 pyruvate molecules enter the mitochondrion • Pyruvate loses a CO2 molecule and becomes acetyl CoA • Krebs cycle produces 2 ATP and CO2 • Electron transport chain produces 34 ATP and water • Aerobic respiration completelyoxidises a glucose molecule • Anaerobic respiration does not completely oxidise glucose – ethanol, lactate and carbon dioxide are by-products

32. Some practice questions on respiration… 1.How do cells capture the energy released by cell respiration? A. They store it in molecules of carbon dioxide. B. They produce glucose. C. The energy is released as pyruvate. D. They produce ATP. (Total 1 mark)

33. Some practice questions on respiration… 2.Which process produces the most ATP per molecule of glucose? A. Anaerobic respiration in a yeast cell B. Aerobic respiration in a bacterial cell C. Glycolysis in a human liver cell D. The formation of lactic acid in a human muscle cell (Total 1 mark)

34. Some practice questions on respiration… 3. Which of the following is the best definition of cell respiration? A. A process needed to use energy, in the form of ATP, to produce organic compounds B. A process used to provide oxygen to the atmosphere C. A controlled release of energy, in the form of ATP, from organic compounds in cells D. A controlled release of energy in the production of food from organic compounds (Total 1 mark)

35. Some practice questions on respiration… 4. Which of the following processes produces CO2? I. Glycolysis II. Alcohol (ethanol) fermentation III. Lactic acid production A. I only B. II only C. I and II only D. I, II and III (Total 1 mark)

36. Some practice questions on respiration… 4. Which of the following processes produces CO2? I. Glycolysis II. Alcohol (ethanol) fermentation III. Lactic acid production A. I only B. II only C. I and II only D. I, II and III (Total 1 mark)

37. Some practice questions on respiration… 4. State a word equation for anaerobic cell respiration in humans. (1 mark)