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Cell Bio > L14. Energy Generation in Mitochondria > Flashcards

L14. Energy Generation in Mitochondria Flashcards

1
Q

explain the electrochemical proton gradient and how it generates ATP - stage 1

A
  • high energy e- are transferred along the electron transport chain
  • the electron transfers then release energy
  • this energy is then used to pump H+ across the membrane
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2
Q

explain the electrochemical proton gradient and how it generates ATP - stage 2

A
  • H+ flows back into the membrane through the ATP synthase
  • this generates ATP from ADP and Pi
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3
Q

explain how the mitochondria can undergo binary fission

A

bc the mitochondria evolved from a prokaryote, it undergoes a fission process similar to bacterial division

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4
Q

how may a mitochondria be localized

A

cells can have mitochondria fixed in one location where there is high ATP use

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5
Q

explain how mitochondria can form long tubular networks

A
  • mitochondria can fuse together and be diffusely distributed through the cytoplasm
  • these networks are dynamic
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6
Q

explain the structure of the mitochondria

A
  • matrix
  • inner membrane
  • outer membrane
  • intermembrane space
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7
Q

mitochondria structure - matrix

A

contains a highly concentrated mixture of hundreds of enzymes

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8
Q

mitochondria structure - inner membrane

A
  • contains proteins that carry out oxidative phosphorylation
  • folded into cristae
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9
Q

mitochondria structure - outer membrane

A
  • contains large channel-forming proteins called prions
  • makes the membrane more permeable than the inner membrane
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10
Q

mitochondria structure - intermembrane space

A

contains enzymes that use ATP passing out of the matrix to phosphorylate other nucleotides

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11
Q

chloroplasts vs mitochondria - what is similar

A
  • inner membrane
  • outer membrane (that is more permeable than inner one)
  • DNA
  • ribosomes
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12
Q

chloroplasts vs mitochondria - what is different

A
  • chloroplasts: stroma and thylakoid membrane
  • mitochondria: matrix
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13
Q

how does the mitochondria catalyze energy conversion

A
  • via oxidative phosphorylation
  • energy released by oxidizing NADH to NAD+ drives phosphorylation of ADP to ATP
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14
Q

explain how acetyl CoA is produced

A
  • fatty acids and sugars enter the intermembrane space through porins in the outer membrane
  • they are then transferred across the inner membrane into the matrix
  • here they are converted into acetyl CoA
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15
Q

explain the role of NADH

A
  • it saves energy derived from oxidation within the citric acid cycle
  • it then donates electron to the electron transport chain and turns into NAD+
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16
Q

how is electron transfer coupled

A
  • electrons are transferred between the activated carrier to O2
  • this step-wise movement of high-energy electrons releases energy
  • that energy is then used to pump H+ across the membrane
17
Q

what are the three respiratory enzyme complexes that transfer electrons

A
  • NADH dehydrogenase complex
  • cytochrome c reductase
  • cytochrome c oxidase complex
18
Q

explain the respiratory enzyme complexes

A
  • they contain metal ions and other groups to facilitate electron transfer
  • electrons are passed from electron carriers with weaker to stronger affinity electron carriers
  • this continues until they combine with a molecule of O2 to form water
19
Q

respiratory enzyme complex - NADH dehydrogenase complex

A

it accepts e- from NADH in the form of H+ and 2e-

20
Q

how can electron transfers move H+

A

e- transfer can move entire hydrogen atoms bc protons are readily accepts from or donated to water

21
Q

electron transfer and movement of H+ - molecule is reduced

A
  • acquired e- brings a negative charge that is neutralized by the addition of a H+ from water
  • net effect is to transfer an entire hydrogen atom
22
Q

electron transfer and movement of H+ - molecule is oxidized

A
  • molecule loses an e- from one of its hydrogen atoms
  • e- is transferred to an electron carrier and H+ is passed to water
23
Q

explain why the orientation of the membrane-embedded e- carrier is important

A
  • the orientation allows e- transfer to drive H+ pumping
  • it does this through oxidation-reduction reactions
24
Q

explain how the orientation of the membrane-embedded e- carrier drives H+ pumping

A
  • protein B picks up a H+ from one side as an e- is passed from A
  • B releases the H+ on the other side of the membrane as it donates an e- to C
25
Q

what are quinones

A
  • they carry e- within the lipid bilayer
  • within the electron transport chain it is called ubiquinone
  • it picks up 1 H+ from the aqueous environment for each e-
  • it can carry 2e- as part of the H atoms
  • it also has a long hydrophobic tail that is embedded within the inner membrane
26
Q

explain redox potential along the mitochondrial e- transport chain

A
  • it increases
  • from least to most redox potential: NAD dehydrogenase complex -> ubiquinone -> cytochrome c reductase complex -> cytochrome c -> cytochrome c oxidase complex
27
Q

explain iron-sulfur centers

A
  • they have a low affinity for e- and iron heme groups serve as an e- acceptor
  • this makes them prominent e- carriers in the early parts of the chain
  • later in the chain, the iron in the heme groups, which are bound to cytochrome centers, are used as e- carriers
28
Q

respiratory enzyme complex - cytochrome c oxidase

A
  • it catalyzes the reduction of O2
  • it is the last e- carrier and has the highest redox potential
  • it removes e- from cytochrome c (oxidizing it) and hands them off to O2
  • reaction: 4e- + 4H+ + O2 -> 2H2O (4 additional H+ pumped out)
29
Q

respiratory enzyme complex: cytochrome c oxidase - what happens after handing e- to O2

A
  • it has a special oxygen binding site that contains a heme group and a copper atom that facilitates the final step (conversion to H2O)
  • once O2 picks up an e-, it forms the superoxide radical O2-
  • the binding site holds the O2- tightly until 4e- are received and converts O2- to H2O
30
Q

respiratory enzyme complex: cytochrome c oxidase - why must O2- be held

A

it is dangerously reactive and can damage DNA

31
Q

explain the ATP synthase motor - forward process

A
  • ATP synthesis
  • it is driven by the H+ gradient
  • the top part (F0 rotor) spins within the stationary head of the bottom part (F1 ATPase)
32
Q

explain the ATP synthase motor - backward process

A
  • ATP hydrolysis
  • facultative anaerobic bacteria can reverse the flow of H+ when they run out of the cell
  • glycolysis-generated ATP is used to pump H+ out of the cell
  • creates a H+ gradient for moving other compounds into the cell
33
Q

explain the electrochemical H+ gradient forces

A
  • the force due to the membrane potential (delta V) is large
  • the force due to the [H+] gradient (pH gradient / delta pH) is smaller
  • these forces combine to generate the proton-motive force which pulls H+ back into the matrix
34
Q

how does the electrochemical H+ gradient facilitate coupled transport

A
  • the pH gradient drives phosphate import and pyruvate import (via 2 different transporters)
  • the voltage gradient drives ADP-ATP exchange

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