Biochemistry and Lab Techniques

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hellosleepy
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162827
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Biochemistry and Lab Techniques
Updated:
2012-07-17 10:57:09
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MCAT
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MCAT OChem
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  1. Hydrolysis reaction -- Ester is cleaved into an alcohol and carboxylic acid 

    In the cell, fatty acids are oxidized in the Krebs cycle 2 Carbons at a time 
  2. Do saturated or unsaturated fats have more energy? 
    Saturated fats have the greatest heat of combustion. More so than unsaturated fatty acids 
  3. What kind of sugar is glucose? What about fructose? 
    Glucose is an ALDOHEXOSE 

    Fructose is a KETOHEXOSE  
  4. 5 membered carbohydrate ring
    Furanose 
  5. 6 membered carbohydrate ring 
    Pyranose 
  6. Alpha and beta structures are what kind of isomers? 
    Anomers 
  7. Electron density shields protons -- higher magnetic field necessary 

    Electron withdrawing groups deshield the proton, less magnetic field strength required. Appear downfield 
  8. How does nmr work? 
    Requires atom with unever atomic or mass number. 

    Such unevenly numbered species' protons experience nuclear spin. - Spin aligned with external magnetic field. 

    When photon shone, the proton will absorb the photon's energy and FLIP/RESONATE to align itself AGAINST the external magnetic field.

    Field of EM = constant, while the magnitude of the magnetic field is varied  
  9. Chemically eq. H's are counted as the same H

    Integral trace gives the relative ratios between the chemically unequivalent Hs in the compound

    Splitting of peaks: dependent on neighboring Hs. N+1 where n is the number of Hs that are neighboring  
  10. C13 nmr 
    can be done because uneven atomic number 

    No splitting  
  11. nmr peak to know 
    Aldehyde at 9.5 ppm! 
  12. What does IR identify?
    Functional groups 

    Bonds in different functional group vary...and they all vibrate at different frequencies

    Heavier atoms resonante at lower frequencies  
  13. How does IR work?
    Every bond has a resonance frequency. 

    When this resonance frequency is matched by the frequency of IR radiation...the IR energy is absorbed.
  14. Important peaks for IR 
    1700 = carbonyl 

    3200-3600 cm-1 = broad OH  
  15. UV spec identifies..? 
    Conjugated system 
  16. How does UV spec work? 
    Pi electrons in conjugated (alternating) bonds can absorb energy and jump to a higher energy level orbital. 

    The initial sample beam intensity will be greater than the reference beam intensity because energy is absorbed by the pi electrons

    The longer the chains of conjugated bonds, the greater the wavelength of absorption

    When a certain wavelength is absorbed, the remaining light will assume the COMPLEMENTARY color to the wavelength absorbed.  
  17. If a compound has 8+ double bonds..
    The absorbance will move into the visible spectrum 
  18. Mass spec. breaks a molecule into ions/functional grps 

    The components are compared on the basis of their mass/charge ratio

    Molecular weight determined from the parent peak (unsplit) and most toward the right hand. 

    Molecules bombarded with electrons. This causes ionization.

    The peaks are abundances of each component of a molecule, and relative to the base peak (the tallest peak)

    Given as percentages of the base peak.  
  19. Radius of curvature of an ion depends of the mass to charge ratio! 

    Ions are accelerated through a magnetic field...this magnetic field exerts a force on the ion, which is what deflects the ions in a curved path 

    More massive and charged ions will have smaller radii of curvature  
  20. Chromatography - purpose and types 
    • Purpose: separate layers of a mixture/solution via polarity differences 
    • Stationary phase = Polar 
    • Mobile phase = solvent, usually nonpolar 

    1. Column - glass beads to inc. SA

    • 2. Paper  - solvent moves up paper vial capillar action which polar components slowly and stick to paper. 
    • Rf factor = (distance compound traveled)/(distance traveled by solvent) 

    3. TLC - slicia gel (polar), need iodine to visualize results

    4. Gas - liquid phase is the stationary phase (polar) while the  mobile phase is a stable, nonpolar gas (like He or N2) . Components of mixture elute through an exit port. 
  21. Distillation 
    Separation based on boiling points. 

    Compound with lower BP/VP will boil first and captured+condensed.

    Fractional distillation is more precise and uses glass beads

    Purifies and separates, but not 100%  
  22. Crystallization
    Based on the principle that pure substances form crystals more easily than impure substances - crystal lattice disrupted by solutes/impurities 

    Not effective method of separation
  23. Extraction 
     
    Separation based on solubility differences 

    1. Add strong acid like HCl - protonates bases in organic layer to make them polar, they can then dissolve into the aqueous layer and dissolve off

    2. Add weak base like NaHCO3 - deprotonates only strong acids, polar acids dissolve off into aqueous layer

    3. Add atrong base like NaOH - deprotonate rest of the acids

    Organic phase --- add to polarize components --- can be separated into the polar aqueous phase and eluted out.  

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