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anomeric carbon

anomeric carbon. Relationship between Haworth (flat ring) depiction and chair-form.

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anomeric carbon

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  1. anomeric carbon

  2. Relationship between Haworth (flat ring) depiction and chair-form Flat ring (Haworth projection) just gives the relative positions of the H and OH at each carbon, one is “above” the other. But it does not tell the positions of the groups relative to the plane of the ring (up, down or out)

  3. Polymers are built by removing a molecule of water between them, known as dehydration, or condensation. R-OH + HO-R → R-O-R + HOH This process does not happen by itself (It is NOT like glucose ring formation) Rather, like virtually all of the reactions in a cell, it requires the aid of a CATALYST Dimer formation

  4. AND: Polymers are broken down by the reverse process, ADDING a molecule of water between them, known as DIMER HYDROLYSIS R-O-R + HOH→ R-OH + HO-R This process does not happen by itself Rather, like virtually all of the reaction in a cell, it requires the aid of a CATALYST

  5. Building a polymer from glucose

  6. Cellobiose with right-hand glucose shown as beta Glycosidic bond Anomeric carbon is always one partner But not here C4 = equatorial out (always in glucose) H O CHOH 4 2 HO H H O 4 CHOH H 2 H H HO HO H H OH HO HO H H Beta-glucose residue “Beta”-glucose residue C1 = equatorial out (in beta glucose) The two glucose molecules are connected in a ~straight line in cellobose Beta conformation is now locked in here

  7. Maltose with right-hand glucose shown as beta Glycosidic bond Anomeric carbon is always one partner H O 4 CHOH 2 H H OH HO HO H H C4 = equatorial out (always in glucose) H O CHOH 4 2 HO H H Alpha-glucose residue H HO HO H C1 = axial down (in alpha glucose) Alpha conformation of –OH is now locked in here “Beta”-glucose residue But not here The two glucose molecules are connected with an angle between them in maltose

  8. Equatorial bond is above the H Equatorial bond is below the H One is forced to draw strange “elbows” when depicting disaccharides using the Haworth projections. Such elbows do not exist in reality. (here the C1 OH is “above” and the C4 OH is “below” Whereas we just saw in actuality that they are both equatorial in beta glucose)

  9. down out H Starch or glycogen chain H Tinker toys Cellulose Tinker toys

  10. 4-1 4-1 C6 4-1 4-1 4-1 6-1 4-1 4-1 4-1 4-1 4-1 Branching in starch Branches at carbon 6 hydroxyl Branching  compact structure Starch or glycogen granules, A storage form of glucose for energy

  11. Cytoplasm Nucleus Organelles Starch granules

  12. down out H H or glycogen chain Cellulose

  13. Cellulose Cell wall of green algae

  14. anomeric carbon anomeric carbon ribose fructose glucose glucose From handout 2-6

  15. More sugars:Mannose C6H12O6 (different arrangement of OH’s and H’s)Galactose C6H12O6 (different arrangement of OH’s and H’s)Deoxyribose C5H10O4 (like ribose but C2’s OH substituted by an H) More disaccharides Lactose = b-1-glucose to C4 of galactose (milk sugar)Sucrose = b-2-fructose to C1- a-1-glucose (table sugar, cane sugar)

  16. Metabolic intermediate (Bacterial cell walls) (Insect exoskeleton)

  17. Lipids • Soluble in organic solvents (like octane, a hydrocarbon) • Heterogeneous class of structures • Not very polymer-like (in terms of covalently bonded structures)

  18. A steroid (Abbreviation convention: Always 4 bonds to carbon. Bonds to H not shown.)

  19. Fats A fatty acid

  20. Ester (functional group, acid + alcohol) A trigyceride (fat)

  21. Effect of fatty acid structure on physical properties cis trans Solid fats cis Oils trans cis

  22. Adipocyte (fat storage cell) Fat globule Nucleus

  23. R=H: a phosphoester (phosphoric acid + alcohol) In this case: phosphatidic acid Note error on handout Handout 2-10 | NH2

  24. [HO] [HO] Handout 2-10

  25. R=another alcohol: A phospho-diester HO HO–CH2CH2N+H3 (alcohol = ethanolamine) HO Handout 2-10

  26. HOH HOH 2 fatty acid tails each Phosphate head Biological membranes are phospholipid bilayers

  27. Incidentally, note the functional groups we have met so far: Hydroxyl Amine Amide Carboxyl Carbonyl Aldehyde Ketone Ester: Carboxylic acid ester Phosphoester And: Glycosidic bonds C=C double bonds (cis and trans)

  28. PROTEINS Amino acids (the monomer of proteins)

  29. At pH 7, ,most amino acids are zwitterions (charged but electrically neutral)

  30. +OH- ( -H+) +H+ 50-50 charged-uncharged at ~ pH2.5 (=the pK) 50-50 charged-uncharged at ~ pH9 (=the pK) Net charge

  31. Numbering (lettering) amino acids ε-amino group ε δ γ β Alpha-carboxyl (attached to the α-carbon) Alpha-amino Alpha-carbon

  32. Amino acid examples

  33. Shown uncharged (as on exams)

  34. Amino acids in 3 dimensions • Asymmetric carbon (4 different groups attached) • Stereoisomers • Rotate polarized light • Optical isomers • Non-superimposable • Mirror images • L and D forms From Purves text

  35. Mannose

  36. Condensation of amino acids to form a polypeptide (must be catalyzed)

  37. Parts of a polypeptide chain

  38. Handout 3-3 The backbone is monotonous (Without showing the R-groups) The backbone is monotonous It is the side chains that provide the variety

  39. “Polypeptides” vs. “proteins” • Polypeptide = amino acids connected in a linear chain (polymer) • Protein = a polypeptide or several associated polypeptides (discussed later) • Often used synonymously • Peptide (as opposed to polypeptide) is smaller, even 2 AAs (dipeptide)

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