Micro Ch. 7

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Micro Ch. 7
2011-11-10 20:21:21

Microbial Physiology: Metabolism of non-glucose substrates
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  1. What is the difference between amylose and amylopectin?
    amylose (straight chain α-1,4 linkage) and amylopectin (straight chain with α-1,6 branches.
  2. 1) What is an amylase?

    2) What is the difference between a-amylase and B-amylase?
    1) an enzyme that allows organisms to metabolize starch

    2) α-amylase is an endogluconase that can chop the chains in monomers, dimers and oligomers (glucose, maltose and dextrin.

    β-amylase is exoglucanase that removes the disaccharide maltose and glucoamylase removes glucose units from the amylose non-reducing end.
  3. What are pullulanase and isoamylase?
    Pullulanse and isoamylase are needed to attack the α-1,6 branches found on amylopectin.

    These enzymes are referred to as debranching enzymes.
  4. 1) What is the structure of cellulose?

    2) How is it hydrolyzed?
    1) It is a straight chain with β-1,4 linkages that forms extensive hydrogen bonding. The structure is very stable.

    2) One hypothesis is that cellulose is attacked in its amorphous regions first by the endo-β-glucanases . Generating dimers (cellobiose) which are degraded by exo-β-glucanases and β-glucosidase.

  5. What is this?
  6. 1) What enzymes degrade pectin?

    2) Name an organism capable of breaking down pectin
    1)Pectin (plant polysaccharide) is degraded first by pectin esterase (which removes a methyl group as methanol) and then pectinase that breaks down the α-1,4 polygalacturonate to monomers of galacturonate

    2) Erwinia carotovora attacks fruits and vegetables dues to its ability to breakdown pectin.
  7. 1) Where is chitin found and what is it's structure?

    2) How is chitin degraded?
    1) Chitin is found in the cell walls of fungi and the exoskeletons of insects and crustaceans. Chitin is poly-β-1,4-N-acetylglusoamine and is second most abundant polymer on earth next to cellulose.

    2) Chitinase breaks the β-1,4 linkage producing monomers of N-acetylglucosamine. Chitin deacetylase removes the acetyl group producing chitosan, which hydrolyzed to glucosamine by chitinase.
  8. 1) What is a disaccharide phosphorylase?

    2) Give an example
    1) Enzymes that phosphorylate a monosaccharide of a disaccharide liberating the other monosaccharide.

    2) Cellobiose (dimer of cellulose) is attacked by cellobiose phosphorylase which produces the following reaction:

    Cellobiose + Pi --->Glucose-1-Ph + Glucose
  9. What are proteinases?
    Proteinases maybe pH specific and recognize peptide bonds between specific amino acid combinations. Alkaline proteases have the broadest activity.
  10. What are lipases?
    Lipases degrade phopholipids or triglycerides into glycerol and fatty acids.
  11. What are DN/RNases?
    DNases and RNases breakdown nucleic acid polymers into nucleotides
  12. Name the enzymes required:
    • 1) hexokinase
    • 2) group translocation or ketohexokinase
    • 3) 1-phosphofructokinase
    • 4) galactokinase
    • 5) glucose:galactose-1-phosphate uridylyl transferase
    • 6) uridine diphosphate glucose epimerase
    • 7) mannose-6-phosphate isomerase
  13. Name the enzymes:
    • 1) arabinose isomerase
    • 2) xylose isomerase
    • 3) ribokinase
    • 4) ribulokinase
    • 5) xylulokinase
    • 6) ribose-5-phosphate isomerase
    • 7) ribulose-5-phosphate-3-epimerase
  14. 1) What is B-Oxidation?

    2) What are the important enzymes and their functions?
    1) The fatty acids are oxidized to acetyl-CoA via the pathway known as b-Oxidation.

    • 2)
    • Acyl CoA synthetase activation step - charges FA
    • Fatty acyl-CoAdehydrogenase -- first step in B-ox -- oxidation; FADH2 formed
    • 3-hydroxyacyl-CoA hydrolyase --Water added
    • L-3-hydroxyacyl-CoA dehydrogenase --Oxidation; NADH + H+ formed
    • acyl-CoA acyltransferase -- Acetyl-CoA split off and CoA added to acyl portion
  15. Name the enzymes in B-Oxidation:
    • 1) Acyl CoA synthetase (activation step)
    • •4 steps of b-Oxidation:
    • 2) Fatty acyl-CoA dehydrogenase
    • 3) 3-hydroxyacyl-CoA dehydrolyase
    • 4) L-3-hydroxyacyl-CoA-dehydrogenase 5) acyl-CoA acyltransferase
  16. 1) What are the products of B-oxidation on an even numbered FA?

    2) Odd numbered?
    1) Acetyl CoA

    2) Acetyl CoA and Propionyl CoA
  17. 1) What happens to propionyl CoA?

    2) What enzyme converts pyruvate to acetyl CoA?

    3) What alternate pathway does E. coli use for propionyl CoA?

    2) pyruvate dehydrogenase

    3) E. coli uses an alternate anaerobic pathway and form pyruvate from propionate via methylcitrate