Today’s Agenda: Variations on photosynthesis (end of yesterday) Variations on electron transport

1. Lecture 9: Cellular Energy Extensions Today’s Agenda: • Variations on photosynthesis (end of yesterday) • Variations on electron transport • Heat generation • Poisons • CSI – ATP • Open review and question time

2. Yesterday’s Exit Ticket H2O CO2 Light NADP+ ADP P + i RuBP 3-Phosphoglycerate Calvin Cycle: Stroma Light Reactions: Thylakoid Membranes ATP G3P NADPH Starch (storage) Chloroplast Fig. 10.21 O2 Sucrose (export)

3. When H2O varies: “C3” Most plants • Stomata can stay wide open • CO2 is relatively unlimited in plant cells In wet environments • Stomata are kept ajar to reduce water loss • CO2 is acquired more slowly More “C4” plants Many grasses In semi-arid environments • Stomata are kept closed in the heat of the day • Stomata are opened at night to acquire CO2 More “CAM” plants Cacti, many other desert succulents In dry environments Light, CO2, H2O, (nutrients) Travelsfy.com; minnestota.publicradio.org; mccullagh.org

4. Most plants (C3 plants) use only Calvin cycle: First product has 3 carbons (phosphoglycerate). H2O CO2 Light NADP+ ADP P + i Light Reactions: Light collection & electron transport RuBP 3-Phosphoglycerate Calvin Cycle ATP G3P Starch (storage) NADPH Chloroplast Fig. 10.21 O2 Sucrose (export)

5. CO2 PEP carboxylase PEP (3C) Oxaloacetate (4C) ADP Malate (4C) ATP Pyruvate (3C) CO2 Calvin Cycle Sugar The C4 pathway Vascular tissue Most plants (C3 plants) use only Calvin cycle: First product has 3 carbons (phosphoglycerate). Some plants (C4 plants) use an additionalCO2 fixation cycle beforethe Calvin cycle: • The enzyme PEP carboxylase “fixes” CO2 into a sugar with 4 carbons • Once enough new CO2 has been stored in the 4-C sugar, it moves into the Calvin Cycle Fig. 10.19

6. C4 plants: • This process allows the Calvin Cycle to run smoothly despite low CO2 conditions Fig. 10.19

7. CO2 PEP carboxylase PEP (3C) Oxaloacetate (4C) ADP Malate (4C) ATP Pyruvate (3C) CO2 Calvin Cycle Sugar The C4 pathway Vascular tissue CAM plants: • Take the C4 process one step further • CO2 is collected and converted to 4-carbon sugar at night • Sugar is storedin vacuoles • In the morning, stomata close and malic acid is broken down to enter the Calvin Cycle

8. H2O CO2 Light NADP+ ADP P + i Light Reactions: Light harvesting and photosynthetic electron transport RuBP 3-Phosphoglycerate Calvin Cycle ATP G3P NADPH Starch (storage) Chloroplast Fig. 10.21 O2 Sucrose (export)

9. Why isn’t every plant a C4 plant? Advantage of C3 plants C3 plantsneed less energy since they don’t run two cycles C3 plants do better than C4 plants in less sunny, moist,cool, CO2-richclimates. Typically more cold-tolerant. Mountainphotographer.com

10. Today’s Agenda: • Variations on electron transport • Heat generation • Cyanide and carbon monoxide • CSI – ATP • Open review and question time

11. Basal metabolic rate, in kcal per day (p. 870) Human, adult maleAdult Alligator 1,600-1,800 60 (at 20°C) Fig. 34.27(e) Fig. 15.6(a)

12. 2nd law of thermodynamics: Every energy transformation leads to a loss of usable energy as heat (=unusable energy)

13. Thermogenesis “warm-blooded” versus “cold-blooded” Endothermic versus ectothermic

14. Brown fat cells produce heat in newborns, small mammals in cold climates, & hibernating animals. Brown fat cells have many mitochondria and use uncoupling proteins to separate electron transport from ATP formation to generate only heat and no ATP http://www.vivo.colostate.edu/hbooks/pathphys/misc_topics/brownfat.html; see Fig. 4.6(a)

15. Fig.8.7 Fig. 10.16 How does the mitochondrial uncoupling protein do this?

16. The mitochondrial uncoupling protein provides a channel across the membrane through which protons (H+) flow back downhill without making ATP, releasing all energy as heat UCP = uncoupling protein H+s have a choice: • Work to get back in (via ATP synthase) • Flow back in for free (via UCP) http://www.nature.com/nrm/journal/v6/n3/fig_tab/nrm1592_F1.html

17. 2009 report on brown fat cells in adult humans too!! http://www.sciencedaily.com/releases/2009/06/090611142529.htm

18. Skunk cabbage in the northeastern US http://www.asknature.org/strategy/7e985ec13e9adf0cbca843df1225fa98 Skunk cabbage in Japan. http://www.damninteresting.com/?author=865 Figure 1   Thermal image of flower of Philodendron selloum during thermogenesis (Ito and Seymour 2005). http://4e.plantphys.net/article.php?ch=e&id=126

19. Electron Thieves: Cyanide H+ H+ H+ ATP synthase H2O 2 H+ + 1/2O2 ADP + ATP H+

20. Fig. 9.16 Intermembrane space H+ H+ H+ Fig.8.7 H+ Protein complex of electron carriers Cyt c Inner membrane V Q   ATP synthase  H2O 2 H+ + 1/2O2 FADH2 FAD NAD+ NADH ADP + ATP P i (carrying electrons from food) H+ 2 1 Electron transport chain & pumping of protons ATP synthesis via H+ flow Mitochondrial matrix Cyanide blocks O2's ability to mop up electrons so NADH and FADH2 never go back to NAD+ and FAD. It also inhibits proton pumping in IV and can “uncouple” proton diffusion from ATP production

21. Dinitrophenol DNP used in 1930s in diet pills after first report on drug's ability to increase metabolic rate. DNP is an uncoupler that moves protons across the inner mitochondrial membrane and releases energy as heat. DNP overdose causes fatal fever. By end of 1938, DNP use no longer legal in US.