Photosynthesis and Cellular Respiration

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Photosynthesis and Cellular Respiration
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Where It StartsPhotosynthesis

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Visible Light

• Wavelengths humans perceive as different colors
• Violet (380 nm) to red (750 nm)
• These wavelengths drive photosynthesis

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Pigments

• Light-catching part of molecule in plants, green
  algae and some bacteria
• often has alternating single and double bonds
• Light energy destabilizes bonds and boosts
  electrons to higher energy levels
• When electrons return to a lower energy level,
  energy is emitted

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Variety of Pigments

• Chlorophylls
• Carotenoids
• Anthocyanins
• Phycobilins

CH3
chlorophyll a
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Photosynthesis Equation
LIGHT ENERGY
12H2O 6CO2
6O2 C6H12O6 6H2O
water
carbon dioxide
oxygen
glucose
water
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Chloroplast
Organelle of photosynthesis in plants and algae
two outer membranes
stroma
Thylakoid inner membrane system connected by
channels.
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Two-Step Process

• Light-dependent reactions
• Light-independent reactions

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sunlight energy
H2O (water)
CO2 (carbon dioxide)
ATP
light- dependent reactions
light- independent reactions
ADP Pi
NADPH
NADP
glucose
O2
H2O (metabolic water)
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Light-Dependent Reactions

• Sunlight required
• Water molecules split
• NADP picks up electrons and hydrogen ion forming
  NADH
• Oxygen escapes to surroundings

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Light-Independent Reactions

• NADPH gives up electrons and hydrogen which
  combine with carbon and oxygen to make glucose
• Requires CO2 and water
• Does not require sunlight
• Uses ATP

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Cellular Respiration
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ATP Is Universal Energy Source

• Photosynthesizers get energy fromthe sun
• Animals get energy second- or third-hand from
  plants or other organisms
• Regardless, the energy is converted to the
  chemical bond energy of ATP

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Main Types of Energy-Releasing Pathways

• Aerobic pathways
• Evolved later
• Require oxygen
• Start with glycolysis in cytoplasm
• Completed in mitochondria

• Anaerobic pathways
• Evolved first
• Dont require oxygen
• Start with glycolysis in cytoplasm
• Completed in cytoplasm

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Glycolysis

• Requires input of 2 ATP
• Does not require oxygen
• Occurs in cytoplasm
• Enzymes partially break down 1 glucose to 2
  pyruvate, 2 NADH and 4 ATP
• Results in a net gain of 2 ATP

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Glucose

• A simple sugar
• (C6H12O6)
• Atoms held together by covalent bonds

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Krebs Cycle

• Occurs in mitochondria
• Requires oxygen
• Pyruvate electrons and hydrogen are picked up by
  NAD and FAD forming 8 NADH and 2 FADH2 CO2 is
  released and 2 ATP form

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Electron Transfer Phosporylation

• Occurs in the mitochondria
• NADH and FADH2 deliver electrons and hydrogen to
  electron transfer chains.
• As electrons are transferred through the chains,
  H and electrical gradients form driving the
  formation of ATP
• Oxygen accepts spent electrons and H to form
  water
• 32 ATP result

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Summary Equation for Cellular Respiration
Glycolysis, Kreb cycle and electron transfer
phosporylation C6H12O6 6O2 6CO2
6 H2O 36 ATP
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Summary of Energy Harvest(per molecule of
glucose)

• Glycolysis
• 2 ATP formed
• Krebs cycle and preparatory reactions
• 2 ATP formed
• Electron transport phosphorylation
• 32 ATP formed

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Fermentation Pathways

• Begin with glycolysis
• Are anaerobic dont require oxygen
• Yield only the 2 ATP from glycolysis
• ATP yield enough for single cell organisms
• ATP yield enough to help cells of multicellular
  organisms through strss times

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Alcoholic Fermentation

• Glycolysis results in ethanol and 2 ATP
• Yeast used to make bread
• Yeast used to make wine

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Lactate Fermentation

• Gycolysis forms lactate and 2 ATP
• Lactobacillus to make cheese and yogurt
• Muscle cells use lactate fermentation when ATP
  demand is intense and brief

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Biochemically Linked Processes

• Photosynthesis
• Energy-storing pathway
• Releases oxygen
• Requires carbon dioxide

• Aerobic Respiration
• Energy-releasing pathway
• Requires oxygen
• Releases carbon dioxide

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Sunlight
Photosynthesis
Organic compounds and oxygen
Carbon dioxide and water
Aerobic Respiration
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Evolution of Metabolic Pathways

• When life originated, atmosphere had little
  oxygen
• Earliest organisms used anaerobic pathways
• Later, noncyclic pathway of photosynthesis
  increased atmospheric oxygen
• Bacteria arose that used oxygen as final acceptor
  in electron transport and became mitochondria
  like
• Predatory cells englufed mitochondria
• Symbiotic relationship developed eukaryotic cells