Harvesting Energy

1. Harvesting Energy • Glycolysis and Cellular Respiration

2. W O R K T O G E T H E R • Why do we humans eat food? What do we need it for, and get out of it?

3. Cellular respiration is an: • Endergonic process • Exergonic process • Exergonic OR endergonic process, depending on the organism.

4. In which organelle does cellular respiration occur? • Chloroplast • Mitochondria • Depends on whether it’s a plant or an animal.

5. What is “food” (i.e. source of metabolic energy) for plants? • Sunlight • Sugar • Water • Oxygen • Minerals

6. Which organisms have mitochondria? • Plants only • Animals only • All Eukaryotic organisms

7. Energy from Glucose • Glycolysis and Cellular Respiration break glucose and other carbon compounds apart. • Energy released from broken bonds is harnessed to make ATP to run cell processes. • ALL Eukaryotic organisms (including plants) carry out cellular respiration ALLTHETIME.

8. Cellular respiration takes place in the mitochondria. mitochondrion outer membrane intermembrane space inner membrane matrix cristae

9. Remember ATP? Adenosine triphosphate, the universal energy carrier, is a single nucleotide (adenine) with two extra phosphate groups attached. ATP is produced in great quantities by mitochondria.

10. Review: ATP is produced and used in coupled reactions glucose exergonic (glucose breakdown) protein endergonic (ATP synthesis) exergonic (ATP breakdown) endergonic (protein synthesis) CO2 + H2O + heat ADP + heat amino acids net exergonic “downhill” reaction

11. Energy released by the exergonic breakdown of glucose is used for: • The endergonic production of ATP. • The exergonic production of ATP. • The endergonic breakdown of ATP. • The exergonic breakdown of ATP.

12. Which of these is true about plants and ATP? • Plants make and store ATP all day to use at night when the sun isn’t available. • Plants carry out cellular respiration day and night to supply their cells with ATP. • Plants use sunlight for energy instead of ATP.

13. Overview Glycolysis splits sugar into two 3-carbon chains (pyruvate), producing 2 ATPs glucose 2 ATP 2 NADH glycolysis (cytosol) 2 pyruvate 2 NADH 2 acetyl CoA Cellular respiration breaks the sugar down further, producing 32-34 ATPs. Krebs (citric acid) cycle 6 NADH 2 ATP (mitochondrion) 2 FADH2 32 or 34 ATPs electron transport chain Total 36 or 38 ATPs NADH and FADH (derived from vitamins B3 and B2) act as electron carriers.

14. in cytosol– no oxygen required glucose 2 ATP glycolysis if no O2 available ethanol + CO2 or lactic acid pyruvate fermentation in mitochondria– oxygen required cellular respiration CO2 34 or 36 ATP O2 H2O

15. Which process produces the most ATP? • Glycolysis • Fermentation • Cellular respiration

16. Glycolysis in cytosol ADP ATP ATP ADP 4 4 2 2 2 2 G3P pyruvate glucose fructose bisphosphate NAD+ NADH 2 2 1 Glucose activation 2 Energy harvest Glucose is split in half. Net gain of 2 ATPs 2 ATPs are used. End product is pyruvate

17. Glycolysis Animation Role of B Vitamins

18. Main points of glycolysis • 6-carbon sugar is split into 3-carbon pyruvate. • 2 molecules of ATP are required for glycolysis, while 4 are produced, for a net gain of 2 ATPs. • Glycolysis supplies some energy, its product (pyruvate) can be broken down further.

19. The products of glycolysis are: • ATP, NADH, pyruvate. • ATP, NADH, G3P. • ATP, NADH, Acetyl CoA. • ATP, pyruvate, CO2.

20. Where does glycolysis take place? • On the cristae of the mitochondria. • In the stroma of the mitochondria. • In the cell’s cytosol outside of the mitochondria.

21. What is the purpose of glycolysis? • Produces sugar. • Splits sugar and releases some energy. • Binds sugar together into polymers. • Uses up excess oxygen.

22. Cellular respiration begins with moving the products of glycolysis into the mitochondrion. 1 Formation of acetyl CoA 3 NADH 3 NAD+ FAD FADH2 CO2 coenzyme A coenzyme A CoA 2 Krebs cycle 2 CO2 acetyl CoA pyruvate NAD+ NADH ADP In cytosol ATP In mitochondrion

23. Krebs Cycle Animation

24. The purpose of the Krebs cycle is: • Produces sugar. • Takes up excess carbon dioxide. • Breaks pyruvate apart, produces energy carriers. • Uses up excess oxygen.

25. The products of the Krebs cycle are: • ATP and NADPH • NADH, FADH2, ATP • CO2 and O2 • Pyruvate and Acetyl CoA

26. Electron carriers from the Krebs cycle are used to power an electron transport chain and proton pump. Oxygen is required to accept energy- depleted electrons. Flow of H+ down concentration gradient powers ATP synthesis. High-energy electron carriers from acetyl CoA formation, Krebs cycle, and glycolysis feed into the ETC. H2O 2e– FADH2 2H+ 1/2O2 NADH ATP ADP + Pi FAD matrix NAD inner membrane intermembrane space Energy from high-energy electrons powers active transport of H+ by ETC. High H+ concentration is generated by active transport. H+ channel is coupled to ATP synthesizing enzyme.

27. Electron Transport Chain Animation

28. Main points of cellular respiration • Cellular respiration takes place in the mitochondria. • The product of glycolysis is broken down completely, releasing CO2 as a waste gas. • The electron transport chain/proton pump complex uses energized electrons to produce up to 36 ATPs from each molecule of glucose.

29. The purpose of the Electron Transport Chain is: • Take in and fix atmospheric carbon dioxide. • Make sugars. • Produce ATP. • Use up excess hydrogen ions.

30. Which of these happens during the electron transport chain? • Carbon dioxide is taken up. • Carbon dioxide is given off. • Oxygen is taken up. • Oxygen is given off.

31. Oxygen taken up during the ETC eventually becomes part of: • Carbon dioxide. • Water. • ATP. • Sugar.

32. Mitochondria animation on XVIVO

33. W O R K T O G E T H E R • We breathe in to supply oxygen to pick up electrons at the end of the electron transport chain. What happens to cellular respiration if we exercise hard and our muscles are using up oxygen faster than we can supply it?

34. glucose (cytosol) In the absence of oxygen, cellular respiration cannot continue. Pyruvate from glycolysis is fermented, producing lactic acid or ethanol. 2 NADH 2 ATP glycolysis lactate Cellular respiration requires oxygen to pick up electrons and protons at the end of an electron transport chain or 2 pyruvate fermentation (no O2) ethanol + CO2 cellular respiration 2 CO2 2 NADH 2 acetyl CoA 4 CO2 Krebs (citric acid) cycle 2 ATP H2O 1/2O2 6 NADH 2H+ 2 FADH2 2e– 32 or 34 ATPs electron transport chain (mitochondrion)

35. If the mitochondria can’t accept pyruvate, NADH from glycolysis accumulates, depleting NAD+. Fermentation uses excess NADH to convert pyruvate to lactic acid or ethanol. regeneration NAD+ NADH NADH NAD+ NADH 2 2 (glycolysis) (fermentation) glucose pyruvate lactate 2 ATP ADP 2

36. True or false: Fermentation is more energy efficient than cellular respiration. • True • False

37. What is so important about the conversion of pyruvate to lactic acid during fermentation? • A large amount of ATP is produced. • NAD+ is regenerated to keep glycolysis going. • Lactic acid can substitute for pyruvate to keep cellular respiration going.

38. W O R K T O G E T H E R • Is oxygen debt a problem in plant cells? Consider: • A leaf cell • A root cell

39. W O R K T O G E T H E R • Can other molecules besides sugar supply energy? Name some molecules that you think are good sources of energy.

40. Fatty acids have more energy per gram than sugars, so are preferred as energy storage. Other monomers can be broken down for energy as well. (cytosol) complex carbohydrates fats proteins glucose amino acids glycerol Glycolysis fatty acids pyruvate acetyl CoA While brain cells usually must have glucose, other cells can use fatty acids and amino acids for energy. Amino acids must be stripped of nitrogen first, which is disposed of in the kidneys. Krebs cycle electron carriers Electron transport chain synthesis breakdown (mitochondrion)

41. What if you take in more monomers than you need to produce ATP? Simple sugars are broken apart in glycolysis. If the mitochondria does not need Acetyl CoA, the acetate is released and can be used to synthesize fatty acids to make fats for storage.

42. Amino acids not needed for protein synthesis are stripped of their amine groups. The remaining carbon backbone can either be used to make Acetyl CoA, or can be used to synthesize fatty acids.

43. What is one possible negative consequence of relying mainly on protein as an energy source? • There are no negative consequences. • Too much nitrogen from metabolism of amino acids can damage the kidneys. • Protein has fewer vitamins than other nutrients.

44. True or false: Fats are harder for the body to process, so you get less energy out of them and store them instead. • True • False

45. Recap • Cellular respiration breaks organic compounds down into inorganic compounds. • In the process, chemical energy in compounds such as sugar is converted to chemical energy in ATP. • ATP is used to run cellular processes. • ALL Eukaryotic organisms carry out cellular respiration.