Ch 18.4

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Ch 18.4
2014-12-01 23:59:26
Test Four
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  1. ·         A molecular assembly in the __ carries out the synthesis of ATP
    o   This enzyme complex was originally called the __ because it was discovered through its catalysis of the reverse reaction, the __
    §  __ emphasizes its actual role in the mitochondrion. It is also called __
    • inner mitochondrial membrane
    • mitochondrial ATPase or F1F0 ATPase
    • hydrolysis of ATP
    • ATP synthase
    • Complex V
  2. ·         How is the oxidation of NADH coupled to the phosphorylation of ADP?
    o   A method was suggested to be of the __
    §  Proposal: __ and __ are couple by a __ across the inner mitochondrial membrane
    ·         The transfer of electrons through the __ leads to the __
    ·         The __ concentration becomes lower in the matrix, and an electric field with the __ __ is generated
    • chemiosmotic hypothesis
    • electron transport and ATP synthesis
    • proton gradient
    • respirator chain
    • pumping of protons from the matrix to the cytoplasmic side of the inner mitochondrial membrane
    • H+
    • matrix side negative
  3. ·         Protons then do what?
    o   This flow of protons drives __ by __
    §  The energy-rich unequal distribution of protons is called the __, which can be thought of as being composed of two components: __ and __
    flow back into the matrix to equalize the distribution

    • the synthesis of ATP by ATP synthase
    • proton-moive force

    a chemical gradient and a charge gradient
  4. o   A chemical gradient for protons can be represented as a __
    o   The charge gradient is created by __ 
    • pH gradient
    • the positive charge on the unequally distributed protons forming the chemical gradient
  5. o   Mitchell proposed htat
    §  __
    ·         Electron transport does generate a __ across the inner mitochondrial membrane
    o   The pH outside is__ units lower than inside, and themembrane potential is __, the outside being __
    • Proton motive force= chemical gradient and charge gradient
    • proton gradient
    •  1.4
    • 0.14 V
    • positive
  6. ·         The role of the respiratory chain was played by bacteriorhodopsin, a membrane protein from halobacteria that pumps proteins when illuminated
    o   Synthetic vesicles containing bacteriorhodopsin and __ purified from beef heart were created
    §  When the vesicles were __, ATP was formed
    ·         The __ and __ are biochemically separate systems, linked only by a __
    • mitochondrial ATP synthase
    • exposed to light
    • respiratory chain and ATP synthase
    • proton-motive force
  7. ·         Electron transport generates a __; and, __ by __ can be powered by a __
    ·         ATP synthase is a __. Much of the “stick” part, called the __, is embedded in the __. The 85-Angstrom-diameter ball, called the __, protrudes into the mitochondrial matrix
    o   The F1 subunit contains the __
    §  In fact, the isolated F1 subunits display __
    • proton-motive force
    • ATP synthesis by ATP synthase
    • proton-motive force
    • large, complex enzyme that looks like a ball on a stick
    • F0 subunit
    • inner mitochondrial membrane
    • F1 subunit
    • catalytic activity of the synthase
    • ATPase activity
  8. ·         The F1 subunit consists of __
    o   The __ and __subunits, which makes up the bulk of the F1, are arranged alternately in a __; they are homologous to one another and are members of the P-loop NTPase family
    §  Both bind __but only the __subunits participate directly in catalysis. 
    • five types of polypeptide chains with the indicated stoichiometry
    • alpha and Beta 
    • hexameric ring
    • nucleotides 
    • Beta
  9. ·         Beginning ust below the __ and __ is a __.
    o   The __subunit includes a long __ that extends into the center of the __
    §  The __subunit breaks the symmetry of the __: each of the beta subunits is distinct by virtue of its interaction with a different face of gama
    • alpha and Beta subunits
    • central stalk consisting of the γ and ε proteins
    • gama 
    • helical coiled coil
    • alpha3-beta3 hexamer
    • gamma 
    • alpha3beta3 hexamer
  10. ·         The __ is a hydrophobic segment that spans the __
    o   F0 contains the __; this channel consists of a ring comprising from __subunits that are embedded in the membrane
    §  A single __ binds to the outside of the ring

    • F0 subunit
    • inner mitochondrial membrane
    • proton channel fo the complex
    • 10 to 14 c 
    • a subunit
  11. ·         The F0 and F1 subunits are connected in two ways:
    • o   By the central γε stalk and by an exterior column
    • The exterior column consists of one a subunit, two b subunits, and the δ subunit
  12. ·         ATP synthase catalyze the formation of ATP from __ and __
    o   The actual substrates are __

    §  A __ of ADP attacks the __ of Pi to form a __intermediate, which then dissociates into ATP and H2O

    o   Enzyme bound ATP forms reaily in the __
    §  When ADP and Pi were added to ATP synthase in H2O, O became incorporated into Pi through the synthesis of ATP and its subsequent hydrolysis
    • ADP and orthophosphate
    • ADP and ATP complexed with Mg2terminal oxygen atom
    • phosphorus atom
    • pentacovalent 
    • absence of a proton-motive force
  13. ·         The rate of incorporation of oxygen into Pi showed that about equal amounts of bound ATP an ADP are in equilibrium at the catalytic site, even in the absence of a proton gradient
    o   ATP does not leave the catalytic site unless __
    §  Thus, the role of the proton gradient is not to __ but to __
    • protons flow through the enzyme
    • form ATP but to release it from the synthase
  14. o   The fact that __ are components of the F1 moiety of the ATPase means that there are __, each performing one of three different functions at any instant. The proton-motive force causes the three active sites to do what as protons flow through the membrane-embedded component of the enzyme
    three beta subunits

    • three active sites on the enzyme
    • sequentially change functions
  15. o   The enzyme can be thought of as having a moving part and a stationary part:
    §  The moving unit (rotor) consisting of the __
    §  The stationary unit (stator) is composed of the remainder fo the molecule
    o   The mechanism is a __
    §  A __subunit can perform each of three sequential steps in the synthesis of ATP by changing conformation
    What are they? 
    §  Interactions with the __ make the three __ subunits unequivalent
    • c ring and the γε stalk
    • binding-change mechanism
    • beta 
    • ·         ADP and P bind
    • ·         ATP synthesis
    • ·         ATP release

    • gamma subunit
    • beta
  16. o   At any given moment, one beta subunit will be in the__
    §  This conformation does what?
    §  A second subunit will be in the __
    ·         This conformation does what?
    • L, or loose, conformation
    • binds ADP and Pi
    • T, or tight, conformation
    • binds ATP with great avidity, so much so that it will convert bound ADP and Pi into ATP
  17. o   Both the T and L conformations are sufficiently __that they cannot __
    §  The final subunit will be in the __
    ·         This form has a more __ and can __
    o   The rotation of the gamma subunit does what?
    §  ADP and Pi bound in the subunit in the __ are doing what?
    • constrained 
    • release bound nucleotides
    • O, or open, form
    • open conformation
    • bind or release adenine nucleotides
    • drives the interconversion of these three forms
    • T form
    • transiently combining to form ATP
  18. o   Suppose:
    §  The gamma subunit is rotated by 120 degrees in a counterclockwise direction
    ·         This rotation does what?
    §  The L form site is __, enabling the transformation of __
    ·         The __in the __ can now depart from the enzyme to be replaced by ADP and Pi
    converts the T form site into an O-form site with the nucleotide bound as ATP

    converted into a T form site

    an additional ADP and Pi into ATP


    O form site
  19. ·         An additional 120-degree rotation converts this __ into __, trapping these substrates
    o   Each subunit progresses from the __ to the __ to the __ with no two subunits ever present in the same conformational form
    §  This mechanism suggests what?
    • O-form site into an L-form site
    • T to the O to the L form
    • that ATP can be synthesized and released by driving the rotation of the gamma subunit in the appropriate direction
  20. ·         Rotation was determined through __, which allowed the __assembly to be immobilized on a glass surface that had been coated with nickel ions
    o   This property of the tags allowed the a3b3 assembly to be immobilized on a glass surface that had been coated with nickel ions
    §  The gamma subunit was linked to a fluorescently labeled __ to provide a long segment that could be observed under a microscope
    o   The addition of ATP caused the actin filament to do what?             
    §  the gamma subunit was __, driven by __
    • tagging
    • a3B3
    • actin filament
    • rotate unidirectionally in a counterclockwise direction
    • rotating, driven by the hydrolysis of ATP
  21. o   the gamma subunit rotates in __, each increment corresponding to the __
    o   the enzyme appears to operate near __; that is, essentially all of the energy released by ATP hydrolysis is converted into __
    • 120 degree increments
    • hydrolysis of a single ATP molecule
    • 100% efficiency
    • rotational motion
  22. ·         How does proton flow through F0 drive the rotation of the gamma subunit?
    o   The mechanism depends on the __
    §  The stationary a subunit directly __
    ·         Although the structure of the a subunit has not yet been experimentally determined, a variety of evidence is consistent with a structure that includes two __
    • structures of the a and c subunits of F0
    • abrupts the membrane-spaning ring formed by 10 to 14 c subunits
    • two hydrophilic half-channels that do not span the membrane
  23. o   Thus, protons can pass into either of these channels, but they cannot __
    §  The a subunit is positioned such that __
    • move completely across the membrane
    • each half-channel directly interactions with one c subunit
  24. ·         Structure of the c subunit: eaech poypeptide chain forms a pair of __ that __. An __ is in the middle of one of the helices
    o   The key to proton movement across the membrane is that, in a proton-rich environment, a __ and will __
    o   The c subunit with the bound proton then does what?
    • alpha helices that span the membrane
    • aspartic acid residue
    • p proton will enter a channel and bind the aspartate residue
    • rotates through the membrane until the aspartic acid is in a proton-poor environment of the other half-channel, where the proton is released
  25. ·         The movement of protons through the half-channels from the high proton concentration of the cytoplasm to the low proton concentration of the matrix powers the __
    o   Its rotation is favored by the __
    §  Thus, the c subunit with the __ moves from __ into the __; and, the other c subunits move in unison
    • rotation of the c ring
    • ability of the newly protonated aspartic acid residue to occupy the hydrophobic environment of the membrane
    • newly protonated aspartic acid
    • contact with the cytoplasmic half-channel
    • membrane
  26. o   The a unit does what as the c ring rotates. Each proton that enters the cytoplasmic half-channel of the a unit moves through the membrane by doing what?
    • remains stationary
    • riding around on the rotating c ring to exit through the matrix half-channel into the proton-poor environment of the matrix
  27. ·         How does the rotation of the c ring lead to the synthesis of ATP?
    o   The c ring is tightly linked to the __
    §  Thus, as the c ring turns, the __ in turn promotes the __through the binding-change mechanism
    §  The rotation of the gamma subunit in turn promotes the __ through the __
    ·         The exterior column formed by the __ prevents the __ unit from rotating
    • gamma and ε subunits
    • gamma and ε subunits
    • synthesis of ATP 
    • synthesis of ATP through the binding-change mechanism
    • two b chains and the delta subunit 
    • alpha3beta3 hexamer
  28. o   The number of c subunits in the c ring appears to range between __, determining the number of protons that must be transported to generate a molecule of ATP
    §  Each 360-degree rotation of the gamma subunit leads to the __
    ·         Thus, if there are 10 c subunits in the ring, each ATP generated requires the transport of __
    o   __ must flow in for each ATP
    o   Electrons from NADH pump enough protons to generate __, whereas those from FADH2 yield __
    • 10 and 14
    • synthesis and release of three molecules of ATP
    • 10/3= 3.33 protons
    • 3 protons
    • 2.5 molecules of ATP
    • 1.5 molecules of ATP
  29. ·         The __ and __ of ATP synthase are members of the P-loop NTPase family of proteins
    o   The P-loop regions of the B subunits will bind either__ or __, depending on __. The conformational changes take place in an orderly way, driven by the __
    • alpha and beta subunits
    •  ADP or ATP
    • which of three different faces of the gamma subunit they interact with
    • rotation of the gamma subunit