Bio 101 Intro' to cellular energy

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Bio 101Intro. to cellular energy
metabolismandPhotosynthesis

• Chapters 6 7

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Intro to energy / metabolism next 4 slides

• Energy (E) is the ability to do work
• vs entropy
• vs equilibrium
• Life is competition
• think limited resources
• think economy
• goal more ATP from less resources
• So, how do organisms get energy from their
  surroundings?

3

• Forms of energy in Biology
• 1. (covalent) bond energy e- energy like
  a rubber band
• a. glucose starch glycogen
  intermediates
• b. ATP main energy currency quick bond
  energy WHEN ADP PO4 energy
  ATP
• c. coenzyme transport bond energy bond
  middle-man made from B vitamins niacin
  riboflavin
• WHERE NAD H NADH FAD H FADH NADP
  H ? NADPH
• 2. Membrane potential (?P) charged Biological
  battery
• ion gradient across a membrane (ETM)
• 3. photochemical energy photons particles
  of light

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Intro. to energy continued

• 3 energy conserving metabolic processes in
  Biology
• 1. respiration (Test 5) 2. fermentation
  (Test 5) 3. photosynthesis
• Metabolism processes involved with energy
  transformation a. catabolism digestion
  breaking bonds exergonic ?S energy
  is released (so it can be captured)
• b. anabolism building forming bonds
  endergonic ?S energy is consumed
  (spent)
• remember the energy roller coaster?

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Oxidation-reduction reactions ie. redox

• Redox reactions transfer of electrons between
  reactants
• - - -
• - A - B - ? - A -
  - B -
• reductant oxidant oxidized
  reduced
• Reductant electron donor Oxidant electron
  acceptor
• LEO Loss of Electrons is Oxidation GER Gain
  of Electrons is Reduction
• NOTE reduce does NOT mean to get smaller
• Complete oxidation mineralization
• glucose ? CO2 (organic ? inorganic)
• Oxidized reduced form of coenzymes?

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• All organisms can be placed in 1 of 2 groups
• 1. primary producers autotrophs self-feeders
• inorganic carbon (CO2) ? organic carbon
  (glucose)
• a. photo(auto)trophs use light energy who
  are they?
• b. litho(auto)trophs use bond energy in
  inorganic reductants ex. sulfide
  H2S H2 NH3 others
• 2. secondary producers heterotrophs who are
  they?
• depend on autotrophs for organic carbon (O.C.)
• O.C. (food) ? O.C. (you)
• CO2 is our exhaust

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Photosynthesis

• Summary
• a. light E ? ?P ? ATP NADPH which is
  then used
• b. CO2 ?ATP NADPH? organic carbon
  (autotrophy)
• a. light reactions depend on light energy
  supplying/converting
• b. dark reactions depend on a. energy
  consuming
• Formula 6 CO2 6 H2O energy ? C6H12O6
  6 O2
• autotrophy
  oxygenic
• Remember the Law of conservation of energy?
  Metabolism?
• Who are the photo(auto)trophs
• plants algae / cyanobacteria / bacteria
  differences?

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continued

• The primary type of photosynthesis discussed is
  both.
• oxygenic H2O used as the reductant O2
  released
• vs you water as the food? No, not for
  energy, but for electrons to form bonds
  (reducing power)
• 6 CO2 ? glucose
• think about what you doto see the
  difference
• AND
• non-cyclic electrons from H2O reduce (and
  leave the light reactions in) NADP ? NADPH vs
  being recycled
• So, no, this doesnt happen all of the time (you
  will see) and some critters do photosynthesis
  differently all of the time.

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The light reactions (next 9 slides)

• The sun is the source fusion reaction H X
  ? He X E The sun is huge 7 x 108
  tons/second fusedyet 1010 years 1 of 10-9 of
  the suns E 1.5 x 1012 tons of O.C. yearly
• Properties of light pg 108 particles
  called photons travel in a line but vibrate
  forms wave pattern with a) frequency
  cycles/sec (Hz) b) wavelength M or
  nM energy of photons is to frequency, so 1/
  to wavelength visible spectrum red is low
  energy, violet is high energy absorbance vs
  transmittance differential absorbance

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Photosynthetic machinery

• Photosynthetic pigments (108) light absorbing
  pigments 1. chlorophyll a 1 pigment
  transmits green 2. accessory pigments
  absorb other colors
• a. porphyrin ring organic box like
  hemoglobin holds an atom of a transition
  metal Mg to capture photon energy?
  excite electrons collapse capture E
  transmits green absorbs most others
• b. hydrocarbon tail non-polar, so. 1.
  make great anti-oxidants 2. to sit happily
  in membrane in a funnel (ie. light
  harvesting complex)

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• Photosynthetic organelle chloroplast plants
  algae only thylakoid photosynthetic ETM
  stacks of thylakoids called grana
  pump H out ? in stroma ?
  thylakoid space
• inverted H gradient vs
  mitochondria

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• The light reactionslike really
• Light reaction machinery combined into a
  Photosystem
• A photosystem is
• a. funnel of light absorbing pigments
  ie. light harvesting complex
• b. reaction center? Redox potential
• c. electron transport system (ETS)
  
• d. proton pump / ATP synthase
  or dehydrogenase

-
_ _ _ _ _
_ _
_
Reaction center
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Oxygenic non-cyclic photosynthesis (ONP)Z
scheme
Contains 2 photosystems
PS2
PS1
_ _ _ _ _
_ _
_ _ _ _ _
_ _
_ _ _ _
Reaction center
e-
Reaction center
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The 1st photosystem PS2
Cholorphyll funnel spark? Rxn center H2O
split (Hill rxn) H2O is the reductant
e- from H2O (?) lifted to top of ETS
this e- dropped through ETS H pump
driven by passing e- H gradient built
(?P) ?P sacrificed to make ATP
via ATP synthase see next
slide ? _
-
e-
_ _ _ _ _
_ _
_ _ _ _ _
?Eh 1.5V !
Reaction center
H
Hill rxn H2O ? e- 2H O also called
photolysis
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• H gradient sacrificed to make ATP via ATP
  synthase
• called photophosphorylation either cyclic
  or non-cyclic

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The 2nd photosystem PS1
Same e- excited again (NO Hill rxn here!!!)
e- dropped through ETS Dehydrogenase
enzyme uses redox power and e- to
reduce NADP (NADP ? NADPH) BUT
thats not the whole story
-
_ _ _ _ _
_ _ _
_ _
Small ?Eh
Reaction center
Dehydrogenase enzyme NADP H e- ?
NADPH remember non-cyclic?
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Non-cyclic vs Cyclic

• The Z-scheme is non-cyclic!!!
  non-cyclic not a circle the e- (from H2O) is
  not recycled the e- (from H2O) ends up
  reducing NADP ? NADPH the e- (from
  H2O) ends up leaving the Z-scheme in NADPH
• BUT what if there is no NADP at the end of PS1?
  no where to put the e- (from
  H2O) the e- must be recycled
  Cyclic shut down PS2
  Why? PS1 is cyclic
  in this case PS1 pumps protons for
  ATP synthesis in this case the
  process is anoxygenic cyclic
• Compare anoxygenic cyclic vs oxygenic
  non-cyclic

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Light reactions summary

• Light dependant..so.pigments necessary
• H2O is the reductant wow!
• Happens in and around thylakoids (in eukaryotes)
• What about cyanobacteria? Works the same way but
  occurs in the cell membrane.
• Products ATP NADPH and oxygen if
  non-cyclic
• Why are the light reactions important (needed)?
• ATP NADPH required for autotrophy
• ie. the Dark reactions depend on the Light
  reactions
• Energy summary Light energy ? ?P ? bond
  energy (ATP NADPH)
• Bacteria 1 cyclic photosystem non-water
  reductants

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The dark reactions (next___ slides)

• Light independent they dont depend on
  light.but.
• They DO depend on the light reactionsfor ATP
  NADPH
• Autotrophy happens here
  6CO2 6 H2O ATP NADPH ? C6H12O6
  6O2 (from light
  rxns) glucose
• So, how is glucose made from CO2 H2O?
• Calvin cycle also called C3 cycle all
  plants use it, but
• done exclusively by C3 plants 85 of
  all plants
• 3 CO2 9 ATP ? ½ of glucose
  (glyceraldehyde 3 PO4-)
• Ribulose bis-phosphate carboxylase (RuBisCo)
• 1 most abundant enzyme? most important?
• 2 cycles (18ATP) 1 glucose vs 36ATP in
  respiration
• (autotrophy) SEE SLIDE ?

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3 CO2
3 x Ribulose bis-phosphate (5)
6 x Phosphoglycerate (3)
6 ATP
3 ATP
.
.
6 NADPH
5 x Glyceraldehyde phosphate (3)
6 x Glyceraldehyde phosphate (3)
Overall 3 CO2 ? ½ glucose
cost 9ATP
1 x Glyceraldehyde phosphate
? The product
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6 CO2 6 H2O ATP, NADPH ? C6H12O6 6 O2

• Stomata holes in leaf surface for gas exchange
• Heat guard cells close to prevent
  transpiration
• Causes ?CO2 and ?O2 inside leaf
• RuBisCo reverses Photorespiration Km
  affinity vs specificity
• Decreases photosynthetic efficiency dramatically
  0.1 8
• C3 plants can deal with this problem as they live
  in higher latitudes, and some in relatively humid
  areas
• But what about other plants.

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Stomata close to prevent transpirationC3
modifications to deal with photorespiration
CO2

• 1. C4 plants C4 cycle thinkwhere
  also called Hatch-Slack pathway ex.
  corn, sugar cane, sorghum
• 2 cell layers
• CO2 shuttle shuttles CO2 from air thru
  mesophyll ? Calvin
• 3 1 4 - 1 3 1 4 - 1 ..
• Enzyme PEP Carboxylase
• cost 12 extra ATP / glucose 18
  (Calvin) 12 30 total

Mesophyll Bundle sheath
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Continued

• 2. Crassulean acid metabolism (CAM)
  thinkwhen Crassulean plant family
  succulents cacti, jade, etc.
• No layers no separation by where
• When does Calvin occur? When is transpiration a
  problem?
• So, open stomata at night, store CO2 with PEP
  carboxylase.
• Chemistry cost like C4 cycle, but PEP
  carboxylase separated from RuBisCo by time
  in CAM plants VS by
  space in C4 plants

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Summary