Chapter 17 Lecture 1

  1. What is the purpose of the citric acid cycle?
    capture electrons
  2. What is a quick summary of the CAC?
    • Acetyl CoA goes through the cycle, causing 2 carbons to be lost as CO2, eight electrons to be captured by electron carriers (NAD+, FAD) 
    • GTP is created, but if ATP is needed, it can be converted to phosphate
  3. Can all amino acids be fed into the pathway?
    • no
    • but acetyl CoA is produced by the addition of 2 acetyl groups to CoA
  4. Where is the location of all of these things?
    in the matrix is the CAC

    inner mitochondrial membrane: pyruvate can't get through on its own--> pyruvate translocase

    outer mitochondrial membrane: has pores, such as porin; certain size, restricting some and allowing others; pyruvate passes through
  5. How can pyruvate get into the matrix?
    transfports pyruvate against the gradient into the matrix; energy source is protons

    • proton concentration outside membrane higher than concentration inside
    • --> proton moves with gradient; pyruvate against (both inside)
  6. What is the final product in the CAC that begins the step?
    oxaloacetate (4 C), which combines with 2 carbons to fourm a 6 carbon ring, to start the cycle
  7. What is oxidative decarboxylation?
    removing one carbon and simultaneously capturing e- 

    NAD+ to NADH
  8. What is the purpose of the ETC?
    to pump protons as electrons are passing dowm

    36 H+ per glucose. These H+ proton gradient power production of ATP by similar protein to bacterial flagellar motor
  9. All enzymes in the ETC are where?
    in the mitochondria

    they are transmembrane integral proteins

    electrons were shuttled directly to ETC, where oxygen acts as the final acceptor, forming water
  10. What is stage 2 of cellular respiration?
    stage 2: remove CO2, capture electrons, get acetyl CoA
  11. What is pyruvate dehydrogenase complex?
    made of 3 different types of enzymes

    • pyruvate dehydrogenase component
    • dihydrolipoyl transacetylase
    • dihydrolipoyl dehydrogenase
  12. What is the simplified version of the reaction?
    pyruvate+ CoA+NAD+--> acetyl CoA+CO2+ NADH
  13. Explain 

    pyruvate dehydrogenase complex
    • E1
    • Number of chains: 24
    • prosthetic group: TPP
    • reaction catalyzed: oxidative decarboxylation of pyruvate
  14. Explain 

    dihydrolipoyl transacetylase
    • E2
    • Number of chains: 24
    • prosthetic group: Lipoamide
    • reaction catalyzed: transfer of acetyl group to CoA
  15. Explain 

    dihidrolipoyl dehydrogenase
    • E3
    • Number of chains: 12
    • prosthetic group: FAD
    • reaction catalyzed: regeneration of the oxidized form of lipoamide
  16. TPP
    1) important part
    2) quality?
    • 1) important part is the ring
    • 2) highly acidic/ can use a proton and bind to pyruvate
  17. Lipoic acid
    we attach it to the end of a lysine residue, allowing it to flop around--> delivery system

    disulfide bond at the end of a large hydrophobic chain; can be broken; we can attach things it
  18. pyruvate to acetyl CoA
    pyruvate--> decarboxylation --> oxidation--> transfer to CoA--> acetyl CoA
  19. What is special about the carbanion of TPP?
    it lost a proton so its in carbanion form. 

    It can then attack the carbonyl carbon of pyruvate to produce hydroxyethyl-TPP

    • A covalent bond forms, doing two things: 
    • ---1) captures energy associated with decarboxylation
    • ---2) allows decarboxylation to happen
  20. In ring structure, __.

    What about Decarboxylation ?

    nitrogen is positively charged, drawing electrons so decarboxylation can take place

    Decarboxylation would not have occurred if it wasn't added to enzyme

    Energy conserved in bond between the prosthetic group
  21. Lipoamide
    2 carbons we want to transfer to CoA

    can form a high energy bond with two carbons

    can flip between active sites
  22. What happens in the pyruvate dehydrogenase component?
    S-S bond breaks

    one side accepts the electrons

    the other side accepts acetyl CoA

    high energy thioester bond
  23. Active site of E2 (Dihydrolipoyl transacetlyase)
    CoA brought in

    high energy bond holding acetyl group

    electrons reduced to disulfide bonds

    exchange bonds
  24. Active site E3
    allows electrons to transfer up the ladder 

    FADH2 transfers electrons to NAD+, becoming NADH
  25. There are ___ through which pyruvate enters--> what happens? 

    gets trapped; nothing can escape and become wasteful
Card Set
Chapter 17 Lecture 1
Test Four