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Biochemistry > Oxidative Phosphorylation (14) > Flashcards

Oxidative Phosphorylation (14) Flashcards

1
Q

Recap question: Aerobic respiration

A

Is the catabolism of nutrients to carbon dioxide, water and energy in the presence of oxygen

-Used by most eukaryotes and prokaryotes

C6H12O6 -> 6O2 + 6H2O + Energy (as ATP)

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2
Q

Recap question

Define catabolism:

A

the breakdown of complex molecules in living organisms to form simpler ones, together with the release of energy; destructive metabolism.

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3
Q

What are the 4 stages of Aerobic Respiration starting with glucose?

A
  1. Glycolysis (independent of oxygen requirement) (don’t need oxygen)
  2. Citric Acid (Krebs) cycle (need oxygen)
  3. Electron Transport Chain (ETC) (need oxygen)
  4. Chemiosmosis (need oxygen)
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4
Q

Glucose metabolic pathways and cell locations:

A

In Eukaryotic Cells,

  1. Glycolysis-occurs in the cytoplasm (outside mitochondrion)
  2. Pyruvate Oxidation-occurs in the mitochondrial matrix
  3. The Krebs cycle-occurs in the mitochondrial matrix
  4. Electron Transport Chain- occurs at the inner mitochondrial membrane
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5
Q

During complete aerobic respiration:

A

1 glucose is completely oxidized by 6CO2

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6
Q

Oxidative phosphorylation:

short definition

A

Electrons get shuffled through complexes in a series of oxidation and reduction reactions

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7
Q

What is Reduction and Oxidation reaction?

A

Reduction reaction: substrate molecules will gain electrons

Oxidation reaction: substrate molecules loses electrons

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8
Q

Electron Transport Chain process:

A
  1. NADH from the krebs cycle migrates here
    - NADH is converted into NAD+ to give up its electron
    - It donates electron to Complex 1
  2. Complex 1 receives the electron, electron causes the complex to gain energy and become supercharged
  3. As Complex 1 is supercharged (activate) it has the energy to pump the protons (4 H+ protons) from the mitochondrial matrix to the intermembrane space. Here we achieve an accumulation of protons on the other side of the membrane
  4. A proton gradient is formed
    - Complex 1 passes its electron to CoQ
    - FADH2 produced from the Krebs
  5. FADH2 is converted to FAD+ to donate an electron to Complex 2
    - It does NOT get supercharged, it gets sent to CoQ
  6. Complex 3 (electrons sitting at CoQ)
    - electrons sitting at CoQ is passed to Complex 3
    - Complex 3 is now Supercharged
    - creates enough energy to pump the proton from the mitochondrial matrix through Complex 3 and into intermembrane space
    - continues to to form a great proton gradient-
  7. Complex 4 and CytC (cytochrome)
    - Electrons (2 H+) from Complex 3 are sent to Cytc then sent to Complex 4
    - Complex 4 is then supercharged
    - great proton gradient continues to form-
  8. Final Electron Acceptor is O2 (Oxygen)
    - Oxygen accept the e- electrons
    - Splits into 2 oxygen ions + protons to make 2 H2O water molecules
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9
Q

What is the goal of the electron transport chain?

A

couple energy stored in electron acceptors to a proton gradient that drives ATP synthesis

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10
Q

What happens

A

As electrons shuffle they lose energy, however, the energy is captured by the complexes of the ETC

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11
Q

What occurs during ATP synthase (after ETC process):

A

ADP wants to convert to ADP but we need an energy source

  1. Proton Gradient
    - High proton gradient to a low proton gradient
    - protons flow from intermembrane space flow down through ATP synthase back to the mitochondrial matrix
  2. Energy input
    - As the protons flow down this acts as an energy input that catalyzes the conversion of ADP to ATP

-that is how energy is formed-

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12
Q

Important things to understand before the Electron Transport Chain and ATP Synthase:

A
  1. Complexes get supercharged by the donation of e- electrons where they gain energy
  2. Pumping of protons are not possible without supercharging and NADH -> NAD+
  3. NADH only sends electrons to Complex 1 and FADH2 only sends electrons to Complex 2 which does not pump electrons
  4. CoQ is the common electron acceptor
  5. Proton gradient -> difference in protons between mitochondrial matrix and intermembrane space
    - Protons move from a high concentration to a low concentration down ATP synthase catalyzing the conversion of ADP to ATP
  6. Oxygen is the Final Electron Acceptor
  7. NADH and FADH2 is from the Citric Acid Cycle
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13
Q

Why is Complex 1 also known as NADH dehydrogenase?

A

removes electron and hydrogen (proton)

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14
Q

What is the function of Coenzyme Q?

A

2nd Electron carrier
Lipid-soluble mobile e- transporter
Transfer e- from Complex 1, 2 and 3

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15
Q

What is the function of Cytochrome C?

A

4th electron carrier
Peripheral membrane protein
Transfer e- from Complex 3 to 4

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16
Q

Where does it result in a high-energy H+ reservoir ?

A

After Complex 4 in the final stages
Protons are accumulated in the intermembrane space through pumping

Intermembrane space result in high-energy H+ reservoir compared to mitochondrial matrix -> protein motive force

17
Q

What is the definition of Oxidative phosphorlyation?

A

The process whereby the energy of e- from the oxidation of substrates (thereby generating reduced NADH and FADH2) in Glycolysis and Krebs Cycle is used to Phosphorylate ADP to ATP

  • It is a series of reactions which couples the oxidation of NADH and FADH2 to the phosphorylation of ADP to generate ATP
  • ETC + Chemiosmosis
18
Q

Why doesn’t Complex 2 have a pump?

A

Too small it doesn’t pass through the membrane

19
Q

What is Substrate level phosphorylation?

A

is a process of forming ATP by the physical addition of a phosphate group to ADP (can take place in the cytoplasm during glycolysis or inside the mitochondrial matrix during the Krebs Cycle)

e.g pyruvate kinase (adds a phosphoryl group to ADP to make ATP) (Substrate-level phosphorylation)

20
Q

Energy molecules from Glycolysis and Krebs Cycle:

A

For 1 glucose in 1 round of Glycolysis

  • 4 ATP molecules&raquo_space; net yield of 2 ATP
  • 2 NADH
  • 2 pyruvate molecules

For 1 glucose (ie 2 Acetyl-CoA) in 2 rounds of Krebs Cycle

  • 2 ATP
  • 8 NADH
  • 2 FADH2

Net total
=10 NADH
=2 FADH2

21
Q

Energy yield, How much energy/ ATP molecules can an electron pair carried by 1 NADH molecule?

A

1 NADH molecule can be used to produce 2.5 ATP molecules

22
Q

What is the force called in the protein gradient that allows the protons to flow down?

A

Proton Motive Force

23
Q

How much energy oxidative phosphorylation yield per mitochondrion and cytoplasmic?

A

Oxidative phosphorylation yields-

  1. 5 ATP per mitochondrion NADH
  2. 5 ATP per cytoplasmic NADH (has less ATP because NADH is from glycolysis and we have to bring the NADH into the mitochondria and it actually loses energy hence less ATP)
24
Q

Energy yield, How much energy/ ATP molecules can an electron pair carried by 1 FADH2 molecule?

And how much does oxidative phosphorylation yied?

A

1 FADH2 molecule can be used to produce 1.5 ATP molecules

Oxidative phosphorylation yields- 1.5 ATP per FADH2

25
Q

What do we need to generate 1 ATP from ATP synthase?

A

To generate 1 ATP, ATP synthase needs to pump 4 H+ ions (protons) from intermembrane space into the matrix

26
Q

What are the 2 reasons for discrepancy? for the generation of ATP molecules from glucose?

How many ATPs generated from 1 glucose molecule?

A
  1. Leaky membranes -> H+ leakage
  2. Cytoplasmic NADH cannot diffuse into mitochondria. It has to be transported in by a “shuttle” molecule:

examples of shuttles (not important)

  • If malate-aspartate shuttle is used= 30 ATPs (NADH enters at complex 1 therefore more H+ can get pumped)
  • If phosphate glycerol shuttle is used= 28 ATPs (NADH enters at complex 2 therefore less H+ can get pumped)

There is no fixed number for how many ATPs you can produce from glucose because we can use different shuttles for NADH and the condition of our mitochondria as we age, the membranes change and get leaky

27
Q

What is the function of an electron in the electron transport chain?

A

To use its free energy to pump protons against their concentration gradient

28
Q

Oxidative phosphorylation yields-

  1. 5 ATP per mitochondrion NADH
  2. 5 ATP per cytoplasmic NADH

Why does is yield less ATP per cytoplasmic NADH?

A

has less ATP because NADH is from glycolysis and we have to bring the NADH into the mitochondria and it actually loses energy hence less ATP

29
Q

Energy yield, during complete aerobic respiration, 1 glucose molecule yields:

A

6 CO2
10 NADH
2 FADH2
Complete Aerobic respiration= Glycolysis + Krebs cycle+ ETC + Chemiosmosis

30
Q

Chemiosmosis definition:

A

the movement of ions across a membrane, movement of H + ions during the production of ATP.

31
Q

Energy yield by 1 glucose:

A

Glycolysis (cytoplasm)
2 ATP
2 cytoplasmic NADH
2 pyruvates

Pyruvate Oxidation (mitochondria)
2 NADH (from 2 pyruvate molecules)

Krebs cycle (2x mitochondria)
2 ATP
6 NADH
2 FADH2

Oxidative phosphorylation (mitochondria): 26-32

Grand total: 30-36 ATPs

Biochemistry (6 decks)

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