Oxidative Phosphorylation (14)

Question 1

Recap question: Aerobic respiration

Answer 1

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)

Question 2

Recap question

Define catabolism:

Answer 2

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

Question 3

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

Answer 3

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)

Question 4

Glucose metabolic pathways and cell locations:

Answer 4

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

Question 5

During complete aerobic respiration:

Answer 5

1 glucose is completely oxidized by 6CO2

Question 6

Oxidative phosphorylation:

short definition

Answer 6

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

Question 7

What is Reduction and Oxidation reaction?

Answer 7

Reduction reaction: substrate molecules will gain electrons

Oxidation reaction: substrate molecules loses electrons

Question 8

Electron Transport Chain process:

Answer 8

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

Question 9

What is the goal of the electron transport chain?

Answer 9

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

Question 10

What happens

Answer 10

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

Question 11

What occurs during ATP synthase (after ETC process):

Answer 11

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-

Question 12

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

Answer 12

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

Question 13

Why is Complex 1 also known as NADH dehydrogenase?

Answer 13

removes electron and hydrogen (proton)

Question 14

What is the function of Coenzyme Q?

Answer 14

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

Question 15

What is the function of Cytochrome C?

Answer 15

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

Question 16

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

Answer 16

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

Question 17

What is the definition of Oxidative phosphorlyation?

Answer 17

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

Question 18

Why doesn’t Complex 2 have a pump?

Answer 18

Too small it doesn’t pass through the membrane

Question 19

What is Substrate level phosphorylation?

Answer 19

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)

Question 20

Energy molecules from Glycolysis and Krebs Cycle:

Answer 20

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

Question 21

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

Answer 21

1 NADH molecule can be used to produce 2.5 ATP molecules

Question 22

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

Answer 22

Proton Motive Force

Question 23

How much energy oxidative phosphorylation yield per mitochondrion and cytoplasmic?

Answer 23

Oxidative phosphorylation yields-

2. 5 ATP per mitochondrion NADH
3. 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)

Question 24

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

And how much does oxidative phosphorylation yied?

Answer 24

1 FADH2 molecule can be used to produce 1.5 ATP molecules

Oxidative phosphorylation yields- 1.5 ATP per FADH2

Question 25

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

Answer 25

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

Question 26

What are the 2 reasons for discrepancy? for the generation of ATP molecules from glucose? How many ATPs generated from 1 glucose molecule?

Answer 26

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

Question 27

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

Answer 27

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

Question 28

Oxidative phosphorylation yields- 2. 5 ATP per mitochondrion NADH 1. 5 ATP per cytoplasmic NADH Why does is yield less ATP per cytoplasmic NADH?

Answer 28

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

Question 29

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

Answer 29

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

Question 30

Chemiosmosis definition:

Answer 30

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

Question 31

Energy yield by 1 glucose:

Answer 31

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