chapter 6 - Biochemical Pathways

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					BIOCHEMICAL
 PATHWAYS
CHAPTERS 6 & 7
All organisms require Energy
        AUTOTROPHS-
   Use basic energy sources to make
    energy containing organic materials
       Glucose
       Sucrose
       Starch
   self-feeders-Make their own food
              AUTOTROPHS
   Photosynthetic autotrophs
     Photosynthesis
     Use light energy & CO2

   Chemosynthetic autotrophs
     chemosynthesis
     Use chemicals (e.g N, S, CHO, Pn) & CO2
         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.

        ATP –
    adenosine
    triphosphate
       A-----P-----P-----P
   High energy
    phosphate bond
       break off a
        phosphate 
        energy is released
       add a phosphate 
        energy is stored
    ATP structure
 Adenine,
 ribose sugar,

 3 phosphates
aerobic cellular respiration - in
one sentence

   convert stable
    glucose molecules
    to ATP, CO2 + H2O
              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
        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
    step one – glycolysis (fig 6.4; 6.7)

   occurs in the
    cytoplasm
   Glucose (6C) -> 2
    pyruvic acid (3C)
   2ATP used
   Generates 4 ATPs
   NAD carries e- & H+
          Transition Step to the Krebs Cycle
                        Aerobic

   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
    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
                    step three –
             electron transport system
   Occurs in the inner mitochondrial membrane

   Electron carriers loaded with electrons and protons from the Kreb’s
    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
Electron Transport System
total ATP’s - 36
 glycolysis - 2
 krebs cycle - 2

 electron transport system -32
    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
          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)
   Aerobic cellular
    respiration vs
    Anaerobic cellular
    respiration
Chapter 7: photosynthesis
        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 -> C6H12O6 + 6O2 + 6H2O


     Reactants =
     Products =
    Chapter 7: photosynthesis     -
   occurs in chloroplasts in
       Eukaryotes


   Occurs in cell membranes in
       prokaryotes
        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
         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
    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)
Summary
   Aerobic Respiration
   Anaerobic Respiration
   Fermentation
   Glycolysis
   Krebs Cycle
   Electron transport system
   Light and dark reactions of photosynthesis
   Autotrophs
   Heterotrophs
   Chemosynthesis

				
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