BIOCHEM Exam 2 Lecture 10

  1. 3 main types of energy molecules used in metabolism
    • carbohydrates
    • lipids (fatty acids)
    • ATP & GTP
  2. carbohydrates are the most abundant biomolecules on earth - list 3 reasons
    • product of photosynthesis
    • oxidation essential for energy in nonphotosynthetic cells
    • structural and recognition functions
  3. empirical formula for MOST carbs

    some also contain N,P,S
  4. monosacharide
    • simple sugars, unbranched C chain backbone
    • single polyhydroxy aldehyde or ketone
    • cyclic (4 or more C)
    • either aldoses or ketoses
  5. oligosaccharide
    • short chains of monosaccharides
    • disaccharides are most abundant
  6. polysaccharide
    • sugar polymers of >20 monosaccharides
    • (glycogen, starch, etc.)
  7. Monosaccharides and stereoisomers
    • contain asymmetric centers --> stereoisomers
    • n chiral centers = 2^n stereoisomers
  8. enantiomers
    have a single chiral carbon and are non-superimposable mirror images
  9. diastereoisomers
    have more than one chiral carbon and are not mirror images
  10. epimers
    diastereomers that differ in configuration around a single chiral C
  11. D and L
    look @ chiral carbon most distant from carbonyl ... OH on right = D, on left =L
  12. aldose numbering
    C1 at the aldehyde carbon
  13. ketose numbering
    C1 at the methoxy attached to the keto group
  14. pyranose
    6 member ring of carbs
  15. furanose
    5 member ring of carbs
  16. alpha and beta anomers
    • look at the methoxy group:
    • oh on the same side as the anomeric carbon = B, opposite = alpha

    • looking at the OH groups:
    • 2 farthest same side = alpha
    • 2 farthest opp = beta
  17. anomeric carbon
    the new chiral carbon that forms when cyclizing
  18. How are monosaccharides joined?
    • covalently by glycosidic bonds
    • form when hydroxyl of one sugar reacts with the anomeric carbon of another
  19. homopolysaccharides
    • contain only a single monomeric species
    • unbranched or branched
    • glucose examples: cellulose, glycogen, starch
  20. heteropolysaccharides
    contains two or more different monomeric species
  21. glycogen
    • energy storage molecule in animal cells
    • highly branched polymer of D-glucose
    • branches ever 8-12 residues
    • each branch ends in non-reducing sugar 
    • glucose units are removed as an energy source from nonreducing ends (may occur simultaneously)
  22. starch
    • energy storage molecule in plants
    • two types
    • -amylose: long unbranched chains of D-glucose
    • -amylopectin: highly branched chains of D-glucose
    • strands of amylopectin form double-helical structures with each other or with amylose strands
  23. cellulose
    • structural, in plant walls
    • water insoluble
    • linear unbranched polymer of D-glucose
    • glucose residues in beta configuration
  24. lipids
    • water insoluble biological molecules
    • chemically diverse
    • storage lipids and structural lipids
    • amphipathic
  25. fatty acids
    • monocarboxylic acids with aliphatic tails
    • heads=polar carboxyl group (pka ~4.5, (-))
    • tails = alkane chains
    • saturated = no double bonds
    • unsaturated = one or more cis double bonds (creates kinks)
  26. fatty acids: longer tail = ?
    • higher melting point
    • more VDW forces between adjacent tails
    • freedom of rotation around single bonds allows tighter packing of tails 
    • this is why sat fat is solid at room temp
  27. fatty acids: more double bonds = ?
    lower melting point

    • kinks interfere with VDW forces and less energy needed to disorder array 
    • this is why unsat. fats are liq at room temp.
  28. omega 3 fatty acids
    • fatty acids with a double bond 3 carbons from the last on carbon on the tail
    • may help reduce serum triglycerides and VLDL
  29. trans fats
    • produced in hydrogenation (add hydrogen) of unsaturated fats
    • partial hydrogenation creates a trans double bond so these trans fats behave more like saturated fats in membranes and in blood
  30. lipids aggregate in water
    • hydrophobic effect (spontaneous)
    • entropically driven
    • -water molecules forced out of hydration
    • -shells around individual lipids
    • -# of fatty acid tails determines nature of lipid association
  31. single-tailed lipids
    • diameter of head exceeds volume of tail
    • forms micelles
  32. double-tailed lipids
    • heads and tails occupy similar diameter space 
    • bilayers favored - eliminates the interaction of water and hydrophobic molecules
  33. three-tailed lipids
    • triacylglycerides
    • cannot form bilayers because the polar heads have small diameter compared with large space occupied by tails 
    • fuel molecules (fat) - stored as droplets in cell
  34. nucleotides
    • comlex nitrogen containing molecules with 3 main functions
    • 1. building blocks of nucleic acids
    • 2. essential for many energy transformations (ATP,GTP)
    • 3. regulates many metabolic pathways (AMP, GMP)
  35. nucleotide has 3 parts
    • sugar: ribose or deoxyribose, most energy nucleotides have ribose
    • nitrogen base: pyrimidines and purines (CUTPY and Pure as AG - bigger name for smaller bases)
    • phosphate
  36. nucleotides vs. nucleosides
    nucleoside = purine or pyrimidine base linked to a 5 carbon sugar

    nucleotide = phosphate ester of nucleoside, one to 3 phosphoryl groups (alpha, beta, gamma)
Card Set
BIOCHEM Exam 2 Lecture 10
exam 2 material