Energy Processing Systems: An Overview

1. Energy Processing Systems: An Overview

2. Big Questions • How do living systems process energy? • How do the energy processing systems of autotrophs and heterotrophs compare? • What are the similarities between prokaryotic and eukaryotic energy processing systems?

3. What’s thepoint? The pointis to makeATP! ATP

4. Energy needs of life • All life needs a constant input of energy • Heterotrophs (Animals): capture free energy from carbon-based chemical compounds produced by other organisms • eat food = other organisms = organic molecules • make energy through respiration • Autotrophs (Plants) • capture free energy from the environment and store it in carbon-based chemical compounds • build organic molecules (CHO) from CO2 • make energy & synthesize sugars through photosynthesis consumers producers

5. + water + energy  glucose + oxygen carbon dioxide glucose + oxygen  carbon + water + energy  C6H12O6 + 6O2 6CO2 + 6H2O + ATP dioxide light energy  6CO2 + 6H2O + + 6O2 C6H12O6 How are they connected? Heterotrophs making energy & organic molecules from ingesting organic molecules oxidation = exergonic Autotrophs Where’s the ATP? making energy & organic molecules from light energy reduction = endergonic

6. Autotrophs: A Bit Deeper Two varieties: Photosynthetic- free energy comes from sunlight. Requires oxygen. Chemosynthetic- free energy comes from inorganic molecules (ex H2S). No oxygen (or light) required.

7. Chemosynthetic Ecosystems

8. Heterotrophs:Harvestingstored energy • Energy is stored in organic molecules • carbohydrates, fats, proteins • Heterotrophs eat these organic molecules  food • digest organic molecules to get… • raw materials for synthesis • fuels for energy

9. glucose + oxygen  energy + water + carbon dioxide respiration ATP + 6H2O + 6CO2 + heat  C6H12O6 + 6O2 COMBUSTION = making a lot of heat energy by burning fuels in one step ATP glucose O2 O2 fuel(carbohydrates) Harvesting stored energy • Glucose is the model • catabolism of glucose to produce ATP RESPIRATION = making ATP (& some heat)by burning fuels in many small steps ATP enzymes CO2 + H2O + heat CO2 + H2O + ATP (+ heat)

10. + + oxidation reduction e- How do we harvest energy from fuels? • Digest large molecules into smaller ones • break bonds & move electrons from one molecule to another • as electrons move they “carry energy” with them • that energy is stored in another bond, released as heat or harvested to make ATP loses e- gains e- oxidized reduced + – e- e- redox

11. e p loses e- gains e- oxidized reduced + – + + H oxidation reduction H  C6H12O6 + 6O2 6CO2 + 6H2O + ATP H How do we move electrons in biology? • Moving electrons in living systems • electrons cannot move alone in cells • electrons move as part of H atom • move H = move electrons oxidation reduction e-

12. oxidation  C6H12O6 + 6O2 6CO2 + 6H2O + ATP reduction Coupling oxidation & reduction • REDOX reactions in respiration • release energy (break C-C bonds in organics) • Strip electrons from C-H bonds: remove H atoms • electrons attracted to more electronegative atoms • in biology, the most electronegative atom? • O2H2O =oxygen has been reduced • couple REDOX reactions & use the released energy to synthesize ATP O2

13. Oxidation adding O removing H loss of electrons releases energy exergonic Reduction removing O adding H gain of electrons stores energy endergonic oxidation  C6H12O6 + 6O2 6CO2 + 6H2O + ATP reduction Oxidation & reduction

14. like $$in the bank O– O– O– O– P P P P –O –O –O –O O– O– O– O– O O O O NAD+ nicotinamide Vitamin B3 niacin O O H H C C NH2 C C NH2 How efficient! Build once,use many ways N+ N+ reduction + H oxidation phosphates adenine ribose sugar Moving electrons in respiration • Electron carriers move electrons by shuttling H atoms around • NAD+NADH (reduced) • FAD+2FADH2 (reduced) reducing power! NADH H carries electrons as a reduced molecule

15. Evolutionary perspective Order of things (for reasons that will be discussed soon): Anaerobic Heterotrophic Nutrition (“fermentation”)  Photosynthetic Nutrition  Aerobic Heterotrophic Nutrition (“aerobic respiration”) Chemosythetic Nutrition (?)

16. Evolutionary perspective Enzymesof glycolysis are“well-conserved” • Prokaryotes • first cells had no organelles • Anaerobic atmosphere • life on Earth first evolved withoutfree oxygen (O2) in atmosphere • energy had to be captured from organic molecules in absence of O2 • Prokaryotes that evolved glycolysis (first step of respiration) are ancestors of all modern life • ALL cells still utilize glycolysis (!) You meanwe’re related?Do I have to invitethem over for the holidays?

17. Is there anything DNA can’t do?

18. But I’m so much more than a stowaway… Any Questions?

19. Review Questions

20. What does a cell need in order to be able to accomplish each of the following: • Heterotrophic nutrition • Autotrophic (photosynthetic) nutrition

21. Provide three pieces of evidence that support the dominant hypothesis for the evolutionary order of energy processing systems in cells, and explain why each piece of evidence provides support: Anaerobic Heterotrophic Nutrition (“fermentation”)  Photosynthetic Nutrition  Aerobic Heterotrophic Nutrition (“aerobic respiration”)

22. 3. Why is it more difficult to establish the origin of chemosynthetic energy processing systems than it is to establish the evolution of non-chemosynthetic modes of energy processing?