Ch 16 Glycolysis Part 3

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Ch 16 Glycolysis Part 3
2014-11-22 21:18:05
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  1. ·         Pyruvate can have three fates: conversion into __, __, or __
    o   The first two are __that take place in the __; a __is an ATP-generating process in which organic compounds act both as the __ and __
    o   in the presence of oxygen, pyruvate is metabolized to __ and __ through the __ and __ with __being the final elecftron acceptor
    • ethanol, lactate, or CO2
    • fermentations 
    • absence of oxygen
    • fermentation 
    • donor and as the acceptor of electrons
    • carbon dioxide and water'CAC and the ETC
    • oxygen
  2. ·         First fate: ethanol is formed from pyruvate in yeast and several other microorganisms. It is two steps
    o   First step: __
    o   Second step: __
    • decarboxylation of pyruvate catalyzed by pyruvate decarboxylase, which requires the coenzyme thiamine pyrophosphate
    • reduction of acetaldehyde to ethanol by NADH catalyzed by alcohol dehydrogenase, regenerating NAD+
  3. o   the __ion is important; it lies in the __ and does what to favor the __
    o   NADH generated by the __ is consumed in the __
    §  No net oxidation reduction in the conversion of glucose into ethanol
    • zinc 
    • active site
    • polarizes the carbonyl group of the substrate
    • transfer of a hydride from NADH
    • oxidation of glyceraldehyde 3-phosphate
    • reduction of acetaldehyde to ethanol
  4. ·         Second fate: lactate is formed from pyruvate in a variety of microorganisms in a process called __; takes place when __; catalyzed by __
    o   There is no net __. The NADH formed in the __  is consumed in the reduction of pyruvate
    o   The regeneration of NAD+ in the __sustains the continued process of glycolysis under anaerobic conditions
    • lactic acid fermentation
    • oxygen is limiting
    • lactate dehydrogenase
    • oxidation-reduciton
    • oxidation of glyceraldehyde 3-phosphate
    • reduction of pyruvate to lactate or ethanol
  5. ·         Third fate: only some energy of glucose is released by fermentation; much more can be extracted aerobically by means of the __ and __; the entry point is __, formed inside mitochondria by __

    ·         __yield only a fraction of the energy available from the complete combustion of glucose. Yet, it is useful because __; and, living organisms, such as oblicate anaerobes, can produce energy without it
    • CAC and the ETC
    • acetyl CoA
    • oxidative decarboxylation of pyruvate

    • Fermentations 
    • oxygen is not required
  6. ·         The three dehydrogenases—__(3)__—have different structures. But, their __ are similar
    o   This nucleotide-binding region is made up of __ and __
    glyceraldehyde 3-phosphate dehydrogenase, alcohol dehydrogenase, and lactate dehydrogenase

    • NAD+-binding domains
    • four alpha helices and a sheet of six parallel beta strands
  7. §  Moreover, in all cases, the bound __ displays nearly the same conformation; it is called the __ and represents  __ that recurs in the __of glycolysis and other enzymes because of their descent from a common ancestor
    • NAD+
    • Rossmann fold
    • primordial dinucleotide-binding domain
    • dehydrogenases
  8. ·         Though glucose is the main fuel, __ and __ are used to
    o   Fructose can take one of two pathways to enter the glycolytic pathway
    §  Much of the ingested fructose is metabolized by the liver, using the __
    ·         Step 1: __of fructose to __ by __
    ·         Step 2: split into __and __ catalyzed by __
    o   __is then phosphorylated to __, a glycolytic intermediate, by __
    §  In other tissues, fructose is phosphorylated to __ by __
    fructose and galactose

    • fructose 1-phosphate pathwy
    • phosphorylation 
    • fructose 1-phosphate
    • fructkinase

    • glyceraldehyde 
    • DHAP
    • fructose 1-phosphate aldolase

    • Glyceraldehyde 
    • glyceraldehyde 3-phosphate
    • triose kinase
    • fructose 6-phosphate by hexokinase
  9. ·         Galactose is converted into __ in four steps in the __
    ·         Lactose intolerance is caused by a deficiency of the enzyme __, which cleaves lactose into glucose and galactose
    • glucose 6-phosphate
    • galactose-glucose interconversion pathway
    • lactase
  10. ·         Lactose is a good energy source for microorganisms in the colon and they __ while __
    o   The gas causes __ and __; it can also draw fluid in, causing diarrhea
    ·         Galactose also causes problems; disruption of galactose metabolism is __
    o   Inherited deficiency in __ activity
    §  Afflicted infants vomit and have __or experience __ and _
    o   __forms, lethargy and retarded mental development
    • ferment it to lactic acid
    • generating methane and hydrogen gas
    • gut distension
    • flatulence
    • galactosemia
    • galactose 1-phosphate uriyl transferase
    • diarrhea 
    • liver enlargement and jaundice
    • Cataracts
  11. ·         The most common ttreatment is to __
    o   If __isn’t active in the lens of the eye, the presence of __ causes the accumulating galactose to be reduced to __, which is osmotically active; water will __, causing __
    • remove galactose from the diet
    • transferase 
    • aldose reductase
    • galactitol
    • diffuse into the lens
    • cataracts