BIOCHEMICAL PATHWAYS

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BIOCHEMICAL PATHWAYS

• CHAPTERS 6 7

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All organisms require Energy
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AUTOTROPHS-

• Use basic energy sources to make energy
  containing organic materials
• Glucose
• Sucrose
• Starch
• self-feeders-Make their own food

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AUTOTROPHS

• Photosynthetic autotrophs
• Photosynthesis
• Use light energy CO2
• Chemosynthetic autotrophs
• chemosynthesis
• Use chemicals (e.g N, S, CHO, Pn) CO2

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HETEROTROPHS

• Obtain energy by breaking down the organic
  molecules they consume.
• Cannot derive energy directly from light or from
  inorganic chemicals, and so must feed on other
  life-forms.

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ATP

• adenosine triphosphate
• A-----P-----P-----P
• High energy phosphate bond
• break off a phosphate ? energy is released
• add a phosphate ? energy is stored

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ATP structure

• Adenine,
• ribose sugar,
• 3 phosphates

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aerobic cellular respiration - in one sentence

• convert stable glucose molecules to ATP, CO2
  H2O

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AEROBIC CELLULAR RESPIRATION

• C6H12O6 6O2 ? 6CO2 6H2O energy (ATP heat)
• Composed of many steps
• biochemical pathway
• Reactants Glucose ingested O2
• Products CO2 H2O
• Where in a cell
• Eukaryotes cytoplasm mitochondria
• Prokaryotes cytoplasm cell membrane

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ACR involves Electron Transfer

• Oxidation / Reduction
• energy containing electrons are transferred from
  one molecule to another
• Oxidation
• large molecule losses e-
• Glucose is oxidized- pulled apart
• Reduction Gain of e-
• e- carriers /coenzymes pick up e and H ions
• Nicotinamide adenine dinucleotide (NAD)
• Flavin adenine dinucleotide (FAD)
• O2 is reduced final e- acceptor

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step one glycolysis (fig 6.4 6.7)

• occurs in the cytoplasm
• Glucose (6C) -gt 2 pyruvic acid (3C)
• 2ATP used
• Generates 4 ATPs
• NAD carries e- H

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Transition Step to the Krebs CycleAerobic

• PA is converted to Acetyl CoA CO2
• Yields NADH
• Occurs in the mitochondria

NAD CO2,
NADH Pyruvate (3 C)
Acetyl-CoA (2 C)
Pyruvate dehydrogenase
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step two - Krebs cycle (Figs 6.5 6.8)

• Named after Hans Krebs
• A British biochemist
• Series of biochemical reactions that are
  catalyzed by enzymes
• Completes break down of glucose
• Hydrogen and electrons are stripped and loaded
  onto NAD and FAD to produce NADH and FADH2
• CO2 released as a byproduct
• 1 ATP per pyruvic acid molecule -gt net 2

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step three electron transport system

• Occurs in the inner mitochondrial membrane
• Electron carriers loaded with electrons and
  protons from the Krebs cycle move to this chain
  - like a series of steps (staircase)
• NADH FADH2 transfer electrons to other
  carriers
• Oxygen final electron acceptor forms water
• Energy released used to synthesize ATP
• ADP P ATP
• Oxidative phosphorylation
• Enzyme is ATP synthase
• Net 32 ATP

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Electron Transport System
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total ATPs - 36

• glycolysis - 2
• krebs cycle - 2
• electron transport system -32

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anaerobic cellular respiration

• Strict anaerobes do not use O2 as terminal e-
  acceptor.
• Use the following instead
• Sulfur N or an organic molecule
• ATP yield lower than in aerobes

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fermentation -

• Anaerobic pathway
• no krebs cycle or ETS
• net ATP 1 or 2
• end products
• Alcoholic fermentation ethanol and CO2 (in yeast
  )
• Lactic Acid fermentation lactic acid (in
  bacteria)

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• Aerobic cellular respiration vs Anaerobic
  cellular respiration

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Chapter 7 photosynthesis
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PHOTOSYNTHESIS

• Is the biochemical process by which plants
  capture energy from sunlight and store it in
  carbohydrates
• Converts light energy to chemical bond energy
• Fixes carbon from CO2
• Biochemical pathway.
• Light energy 6CO2 12H2O -gt C6H12O6 6O2
  6H2O
• Reactants
• Products

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Chapter 7 photosynthesis -

• occurs in chloroplasts in
• Eukaryotes
• Occurs in cell membranes in
• prokaryotes

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step 1 - light capturing

• occurs in the chloroplasts
• In Grana or Thylakoid membranes
• chlorophyll absorbs light energy
• Chlorophyll a b
• e- get excited due to added energy

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step 2 - light dependent reaction Light Reaction

• Occurs in Grana
• Excited electrons used for
• Making ATP oxidative phosphorylation
• Enzymes split H2O e- and H
• O2 released
• NADP used as a coenzyme
• ATP, NADPH go into the Stroma

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step 3 - light independent reaction Dark
Reaction/Calvin cycle

• Occurs in the stroma
• ATP donates energy to link C, H, O
• NADPH donates hydrogen
• CO2 used as a carbon source
• Linked to 5 carbon starter molecules Ribulose(
  5-C sugar)
• Enzyme is ribulose biphosphate carboxylase
  (RuBisCo)
• Product is 2 molecules of glyceraldehyde 3
  Phosphate PGAL
• Surplus G-3-P used to make glucose or other
  molecules (proteins, nucleic acids, etc)

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Summary

• Aerobic Respiration
• Anaerobic Respiration
• Fermentation
• Glycolysis
• Krebs Cycle
• Electron transport system
• Light and dark reactions of photosynthesis
• Autotrophs
• Heterotrophs
• Chemosynthesis