Chapter 16 Lecture

Card Set Information

Chapter 16 Lecture
2014-11-17 13:48:49
Test four
Show Answers:

  1. Muscles work better when?
    when O2 is aroud
  2. What are the pathways glucose can go through?
    Glucose --(glycolysis)-->pyruvate-->

    (fermentation)--> ethanol or lactate

    (O2)--> Complete oxidation
  3. D-Glucose

    Why does it covert?
    monosaccharide; six carbon aldose

    We want the carbon exposed because its a potential site for phosphorylation; we need two sites though, so we have to convert it to a ketone
  4. Fructose has __. 

    Lots of __ to be removed and use as __. 

    Any enzyme working on it only works on an __.
    two potential phosphorylation sites

    • electrons
    • sources

    open ring form (has to open it up)
  5. Eversion
    binding site of one side of cell opens to other side of cell
  6. GLUT4
    glucose transport protein
  7. Explain the family of glucose transporters.
    members of family of proteins that have structure in common

    12 transmembrane segments

    all single polypeptide chains (500 amino acids long)

    binding sites for glucose in extracellular domain, always on outside
  8. Glucose transport proteins arrangement in the membrane?
    don't stretch out; form a more complex unit; undergo eversion to get glucose out of cell
  9. What do the different forms of glucose transport proteins affect?
    affinity for glucose

    enables cells that really need energy in times of distress to get it
  10. What would a low Km and high Km indicate for the glucose transporters?
    low Km: binds glucose at low concentration: high affinity

    high Km: binds at high concentration
  11. Once glucose is in the cell, what happens?
    it can go through a pathway
  12. Stages of the glycolytic pathway.
    stage one: investment and cleavage--> 6 carbon glucose--> 2 3 carbon phosphorylated molecules

    2 ATP are lost

    Stage 2: net gain phase
  13. If glucose gets out, what happens?
    you can't get energy from it. Keep it in by changing characteristics
  14. 1st step of glycolysis results in __.
    one molecule of ATP lost
  15. Why is hexokinase unique?
    not active until substrates are bound; induced fit model of activity; suggests a conformational change
  16. Inactive form of hexokinase?
    hexokinase has a hinge open. You don't want ATP in active site, hydrolyzed for no reason. 

    Closes when glucose binds, changes conformation, hinge closes, and 2 lobes come closer; a hydrophobic pocket forms--> ATP binds--> hydrolysis
  17. What is wrong with glucose 6-phosphate an what has to change?
    • there is no substrate in ring form. 
    • So, its opened up. Yet, in its open chain form, it is an alehyde, which isn't useful because we want a free carbon. 

    It is converted to fructose 6-phosphate, which is converted to its ring form.

    SUMMARY: G6P is converted to F6P by opening it, isomerizing it, and reforming the five carbon ring
  18. Committed step of glycolysis
    you can't back up or remake the ATP
  19. ATP is a __.

    Changing up the molecule and creating something that __.

    has high transfer phosphoryl potential
  20. What is the last step of the first stage of the pathway?
    chop it in half to two  different reverse aldol condensation

    2 3 carbon sugars form--> DHAP (dihydroxyacetone) and GAP (glyceraldehyde 3-phosphate)

    last part of stage 1 is conversion of DHAP to GAP
  21. GAP does what?

    DHAP does what?
    GAP: next substrate in pathway

    DHAP: must be converted to GAP
  22. What is the structure of triose phosphate isomerase?
    unique structure: antiparallel beta sheets--> barrel/ alpha helices

    important amino acid side chains= histidine and glutamic acid
  23. What is important about the loop?
    important because a conformational change occurs with that loop of protein 

    connects beta sheet core to alpha helix (periphery)
  24. What does the enediol intermediate need to be ?
    needs to be trapped
  25. What is the main goal of the triose phosphate isomerase?
    • transfer electrons from one another
    • side chains needed for this

    Key: enediol intermediate (unstable) gets phosphorylated
  26. What is the first step of the triose phosphate isomerase reaction?

    What is the purpose of the loop?
    Stage 1: invested one ATP to get phosphate or--> highly unstable

    it closes down like a lid on the active site and locks the enediol intermediate, preventing its release until reaction is complete
  27. Summarize part one?
    Invested energy to charge up to part where it has some phosphoryl potential but not able to transfer it yet
  28. What is stage two all about?
    generate a molecule with high transfer ph. potential
  29. What does glyceraldehyde 3- phosphate dehydrogenase?
    Take inorganic phosphate and add to substrate

    1,3-bisphosphate--> prohibited
  30. How to get the glyceraldehyde 3-phosphate dehyrogenase reaction to happen?
    dehydrogenase: enzyme that couples two reactions; the highly unfavorable with the highly favorable

    remove electrons and protons with release of free energy
  31. How is energy captured when coupling reactions?
    in the thioester intermediate

    a phosphate in a covalent bond between enzyme and substrate
  32. What is another cofactor?
  33. In the glyceraldehyde 3- phosphate dehydrogenase reaction, what needs to happen?

    What is the key?
    remove electrons from teh carbonyl carbon and donate to NAD+. To do this, cysteine acts as a nucleotide, drawing electrons to it and making transfer easier. 

    cysteine acts as nucleophile
  34. What is the second step in the glyceralehyde-3-phosphate dehydrogenase pathwy?
    evidence shows NADH must leave and be replaced by NAD+ 

    product:1,3- BPG