Today’s Agenda:
• Variations on photosynthesis (end of yesterday)• Variations on electron transport
• Heat generation• Poisons
• CSI – ATP• Open review and question time
Lecture 9: Cellular Energy Extensions
LightReactions:Thylakoid
Membranes
CO2
NADP+ADPPi+
RuBP
3-PhosphoglycerateCalv
inCycl
e:StromaG3P
ATP
NADPH
Starch(storage)
Sucrose (export)
Chloroplast
Light
H2O
O2Fig. 10.21
Yesterday’s Exit Ticket
When H2O varies:
Light, CO2, H2O, (nutrients)Travelsfy.com; minnestota.publicradio.org; mccullagh.org
In wet environments • Stomata can stay wide open• CO2 is relatively unlimited in
plant cells
In semi-arid environments
• Stomata are kept ajar to reduce water loss
• CO2 is acquired more slowly
In dry environments
• Stomata are kept closed in the heat of the day
• Stomata are opened at night to acquire CO2
“C3”Most plants
More “C4” plantsMany grasses
More “CAM” plantsCacti, many other desert succulents
Most plants (C3 plants) use only Calvin cycle: First product has 3 carbons (phosphoglycerate).
LightReactions:
Light collection & electron transport
CO2
NADP+
ADP
Pi+
RuBP
3-Phosphoglycerat
eCalv
inCycl
e
G3P
ATP
NADPH
Starch(storage)
Sucrose (export)
Chloroplast
Light
H2O
O2Fig. 10.21
Most plants (C3 plants) use only Calvin cycle: First product has 3 carbons (phosphoglycerate).
Fig. 10.19
The C4 pathway
CO2PEP carboxylase
Oxaloacetate (4C)
Malate (4C)
PEP (3C) AD
PATP
Pyruvate (3C)CO2
CalvinCycle
Sugar
Vasculartissue
Some plants (C4 plants) use an additional CO2 fixation cycle before the 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
C4 plants:• This process allows the Calvin Cycle to run smoothly
despite low CO2 conditions
Fig. 10.19
The C4 pathway
CO2PEP carboxylase
Oxaloacetate (4C)
Malate (4C)
PEP (3C) AD
PATP
Pyruvate (3C)CO2
CalvinCycle
Sugar
Vasculartissue
CAM plants:• Take the C4 process one step further
• CO2 is collected and converted to 4-carbon sugar at night
• Sugar is stored in vacuoles
• In the morning, stomata close and malic acid is broken down to enter the Calvin Cycle
LightReactions:
Light harvestingand photosynthetic electron transport
CO2
NADP+
ADP
Pi+
RuBP
3-Phosphoglycerate
CalvinCycleG3PATP
NADPH Starch(storage)
Sucrose (export)
Chloroplast
Light
H2O
O2
Fig. 10.21
Why isn’t every plant a C4 plant?
Advantage of C3 plants
C3 plants need less energy since they don’t run two cycles
C3 plants do better than C4 plants in less sunny, moist, cool, CO2-rich climates. Typically more cold-tolerant.
Mountainphotographer.com
Today’s Agenda:
• Variations on electron transport• Heat generation• Cyanide and carbon monoxide
• CSI – ATP• Open review and question time
Fig. 34.27(e)
Basal metabolic rate, in kcal per day (p. 870)
Human, adult male Adult Alligator 1,600-1,800 60 (at 20°C)
Fig. 15.6(a)
2nd law of thermodynamics: Every energy transformation leads to a loss of usable energy as heat (=unusable energy)
Thermogenesis“warm-blooded” versus “cold-blooded” Endothermic versus ectothermic
http://www.vivo.colostate.edu/hbooks/pathphys/misc_topics/brownfat.html; see Fig. 4.6(a)
Brown fat cells have many mitochondria
Brown fat cells produce heat in newborns, small mammals in cold climates, & hibernating animals.
and use uncoupling proteins to separate electron transport from ATP formation to generate only heat and no ATP
Fig. 10.16
How does the mitochondrial uncoupling protein do this?
Fig.8.7
http://www.nature.com/nrm/journal/v6/n3/fig_tab/nrm1592_F1.html
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)
2009 report on brown fat cells in adult humans too!!
http://www.sciencedaily.com/releases/2009/06/090611142529.htm
Skunk cabbage in Japan.
http://www.asknature.org/strategy/7e985ec13e9adf0cbca843df1225fa98
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
Skunk cabbage in the northeastern US
http://www.damninteresting.com/?author=865
Electron Thieves: Cyanide
2 H+ + 1/2O2
H2OADP +
H+
ATP synthase
ATP
H+
H+H+
Fig.8.7 Protein complexof electroncarriers
H+
H+H+
Cyt c
Q
V
FADH2 FADNAD+NADH
(carrying electronsfrom food)
Electron transport chain & pumping of protons
2 H+ + 1/2O2 H2O
ADP + Pi
H+
H+
ATP synthase
ATP
21
Intermembranespace
Mitochondrial matrix
Innermembrane
Fig. 9.16
ATP synthesis via H+ flow
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
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.