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SMP - MNE Exam 1 > Lecture 14: Oxidative Phosphorylation & Glycolysis > Flashcards

Lecture 14: Oxidative Phosphorylation & Glycolysis Flashcards

1
Q

Which complex of the respirasome does not pump out protons?

A

Complex II

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2
Q

Describe the 4 steps happening in Complex I

A
  1. NADH gives 2 e- to FMN or FAD, fully reducing it to FMNH2/FADH2
  2. The e- travel through a series of iron-sulfur clusters
  3. The 2 e- bind coenzyme-Q which also takes 2 H+ (1 from NADH and 1 from matrix) to become fully reduced to QH2
  4. 4 H+ are pumped out of the matrix using the energy generated by QH2 formation
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3
Q

What is the net equation of Complex I?

A

NADH + Q + 5 H+ (matrix) –> NAD+ + QH2 + 4 H+ (IMS)

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4
Q

What happens in the 2 steps of Complex II? 3 options

A

OPTION 1

  1. H2 is transferred from succinate to FAD forming FADH2 and fumarate
  2. H2 is transferred from FADH2 to Q

OPTION 2

  1. H2 is transferred from glycerol-3-phosphate to FAD forming FADH2 and DHAP
  2. H2 is transferred from FADH2 to Q

OPTION 3

  1. Palmitoyl-CoA is oxidized to trans-Δ^2-enoyl-CoA forming FADH2
  2. H2 is transferred from FADH2 to Q
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5
Q

Why does NADH generate more ATP then FADH2?

A

Because FADH2 is used in Complex II, which does not pump protons into the IMS (aka does not contribute to the proton gradient)

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6
Q

What about coenzyme-Q allows it to efficiently pump H+ out of the matrix via Complex 3?

A

It can adopt multiple intermediate states and radical forms

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7
Q

What electrochemical gradient is created during the ETC?

A

H+ pumped out of matrix into IMS

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8
Q

What do FMN and FAD stand for?

A

Flavin MonoNucleotide

Flavin Adenine Dinucleotide

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9
Q

From what vitamin family is riboflavin from?

A

Vitamin B

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10
Q

What part of FMN and FAD accept electrons in Complex I of the ETC?

A

Their isoalloxazine ring

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11
Q

Describe the iron-sulfur clusters of Complex I of the ETC?

A

Iron is held in place by sulfur from cysteine residues

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12
Q

What are the 2 charge states of iron?

A

Ferric: Fe3+
Ferrous: Fe2+

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13
Q

What about Q allows it to be in the inner membrane of the mitochondria? What does this mean?

A

Long isoprenoid side chain which makes it very soluble in the inner membrane –> exists as a pool of Q and QH2 to mediate the respirasome

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14
Q

How do you call the oxidized form of coenzyme Q (Q0?

A

Ubiquinone

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15
Q

How do you call the reduced form of coenzyme Q (QH2)?

A

Ubiquinol

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16
Q

Describe the structure of coenzyme Q

A

Benzoquinone ring with isoprenoid side chain

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17
Q

What is the end goal of Complex 4? What does it require?

A

Catalyzes the transfer of 4 e- to reduce O2 into H2O: requires 4 cytochrome c molecules, meaning outputs from previous complexes need to be doubled

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18
Q

What is the net equation of the rxn happening at Complex III?

A

2 QH2 + Q + 2 cyt Cox + 2 H+ –> 2 Q + QH2 + 2 cyt Cred + 4 H+ (pumped out)

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19
Q

How many H+ pumped out in complex III?

A

4

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20
Q

How many H+ pumped out in complex IV?

A

2

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21
Q

What do Complex III, IV and cyt C all have in common? Purpose? Difference with that found in blood?

A

Heme group cofactor which contains iron to accept/donate electrons
Different from heme in Hb because it accepts and donates electrons instead of staying in Fe2+ state to bind O2

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22
Q

How is the electrochemical potential used to create ATP?

A

The F0-F1 ATPase or ATPsynthase uses it:

  • F0 lets protons back in the matrix
  • F1 uses this energy to catalyze the production of ATP from ADP and Pi
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23
Q

What does the pumping of H+ into the IMS create? What’s important to note?

A
  1. Electrical potential: more positive in IMS
  2. Chemical potential: more acidic in IMS
    BOTH ARE LOCAL, NOT ENTIRE IMS AND CYTOSOL
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24
Q

What happens if there are low levels of ADP and Pi in the mito matrix?

A

The flow of H+ through F0 will decrease

25
Q

What happens when O2 is lacking in the mito? Why would this happen? What mechanism helps during these circumstances?

A

In asphyxiation or ischemia there is a lack of O2 so electrons are not able to go through the complexes and protons are not pumped –> the electrochemical gradient collapses and the F1F0-ATPase switches its catalytic activity from ATP synthesis to ATP hydrolysis to recreate the gradient. This can deplete ATP stores and be lethal.
However, the build up of pyruvate and lactate in IMS from glycolysis cause a drop in pH so protons (K+) are pumped back into IMS, causing a drop in pH inside and activating the IF-1 inhibitor, which will inhibit the the ATP hydrolase activity of the F1F0-ATPase to salvage remaining ATP.

26
Q

What is the role of adenine nucleotide translocase? Where is it located? How does this affect the electrical potential?

A

Antiporter that transport ATP from matrix to IMS in exchange for ADP (on inner membrane of mito)
Decreases electrical potential (more negative outside) because ATP has 4 (-) charges and ADP only has 3

27
Q

What is the role of the phosphate translocase? Where is it located?

A

Symporter that transports uses proton gradient to transport inorganic phosphate (H2PO4-) and H+ inside the matrix (on inner membrane of mito)

28
Q

How many protons pumped from 2 electrons donated by NADH?

A

10

29
Q

How many protons pumped from 2 electrons donated by succinate?

A

6

30
Q

How many H+ are needed to make 1 ATP?

A

4

31
Q

How much ATP per 1 NADH?

A

2.5

32
Q

How much ATP per 1 succinate?

A

1.5

33
Q

What is the rate of respiration mainly regulated by?

A

The level of ADP in the matrix

34
Q

What is an example of when ADP does not regulate the rate of respiration? What types of people have a lot of this?

A

Brown fat has lots of mito and uncoupling proteins uncouple respiration and use the proton gradient to release energy in the form of heat
Infants have a lot of brown fat to keep warm

35
Q

Why is brown fat brown?

A

Because it has a lot of mito, so a lot of heme groups which are brown

36
Q

How does cyanide poisoning affect the ETC?

A
  1. Cyanide binds to Fe3+ (ferric iron) in the heme of cytochrome a and a3 in Complex IV, preventing it from accepting electrons and being reduced
  2. Flow of electrons to O2 is blocked as well as all of the previous steps up to NADH oxidation
37
Q

What is the treatment for cyanide poisoning? Explain how this works.

A

Amyl nitrite inhalation or IV infusion with NaNO2 (sodium nitrite) which will be reduced to nitrate and will convert oxyhemoglobin to methemoglobin (Fe2 + to Fe3+), which can then easily bind cyanide and is converted to thiocyanate which is excreted

38
Q

What is the main purpose of glycolysis in muscle?

A

ATP production under anaerobic conditions to make pyruvate which is converted to lactate

39
Q

What is the side-product of glycolysis under anaerobic conditions?

A

Lactate production

40
Q

What is the main purpose of glycolysis in the liver?

A

Anabolic process to make FAs from excess glucose

41
Q

What is the main purpose of glycolysis in the brain?

A

ATP production under aerobic conditions

42
Q

Can the brain perform anaerobic glycolysis?

A

NOPE

43
Q

What is the main purpose of glycolysis in RBCs?

A

ATP production under anaerobic conditions to make pyruvate which is converted to lactate

44
Q

Do RBCs perform glycolysis aerobically or anaerobically?

A

Anaerobically

45
Q

Describe what happens in an actively contracting muscle in terms of metabolism.

A

The rate of glycolysis far exceeds that of the citric acid cycle, and much of the pyruvate formed is reduced to lactate, some of which flows to the liver, where it is converted into glucose

46
Q

What are the 2 sides of the mito inner membrane called?

A

Inside: N-side (negative)
Outside: P-side (positive)

47
Q

What is FMN usually attached to? How?

A

A protein, very tightly bound

48
Q

What is another important role of coenzyme-Q?

A

Bind to ROS

49
Q

Is coenzyme Q synthesized by the body?

A

YUP

50
Q

What kind of molecule is cytochrome C? Where is it located

A

Protein in the IMS

51
Q

How many electrons can 1 cyt C accept?

A

1

52
Q

Compare F-Type ATPase found in lysosome vesicle to F-Type ATPsynthase of inner mito membrane.

A

Exact same but working in reverse.

53
Q

How much ATP for 1 glucose through oxidative phosphorylation?

A

30 or 32

54
Q

What happens when a cell looses its ATP pool?

A

Cell death

55
Q

How many electrons can Fe3+ accept?

A

1

56
Q

Where is cytochrome C located?

A

Intermembrane space

57
Q

In what kind of muscles is brown fat found?

A

Slow twitch that use fat as fuel

58
Q

What is thermogenin?

A

Uncoupling protein

59
Q

Which step of complex 4 does cyanide inhibit?

A

The cytochrome oxidase step

SMP - MNE Exam 1 (25 decks)

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