Module 9 - Electron Transport Chain

Question 1

Electron transport chain is..

Answer 1

series of protein complexes embedded in mitochondrial membrane
○E- captured from donor molecules are transferred through these complexes

Question 2

What are complexes found in the e transport chain

Answer 2

NADH dehydrogenase, succinate dehydrogenase, cytochrome c reductase, cytochrome c oxidase, ATP synthase

Question 3

What are the mobible carrier involved in etc

Answer 3

ubiquinone and cytochrome c

Question 4

What are other key components of ETC

Answer 4

NADH and its e-, H+ , O2, water and ADP and Pi which combine to make ATP

Question 5

Give a breif overview of the electron transport chain

FUCK THIS QUESTION

Answer 5

●At start of e- transport chain two e- passed from NADH into NADH dehydrogenase complex
○One H for each e- coupled with this
●Next 2 e- transferred to ubiquinone
○Ubiquinone is called mobile transfer molecule which moves e- to cytochrome b-c1 complex to cytochrome c
●Cytochrome c then accepts each e- one at a time and one H+ pumped through complex as each e- is transferred
● Next in the cytochrome oxidase complex, 4 e- required that interact with molecular oxygen to form two water molecules
○Other 4 H+ are pumped across membrane
○This series of H+ pumping creates gradient
○The potential energy in this gradient is used by ATP synthase to make ATP from ADP and inorganic phosphate

Question 6

What is the structure of the electron transport chain (protein compelces)

Answer 6

Made of 5 protein compleces embedded w/in inner mitochondrial membrane
Protein complex 1,2,3,4,5

Question 7

What is role of the first complex

Answer 7

• in general the role of the first complex is
  1. Accept 2 e- from NADH and shuttle them along
  2. Pump 4 protons out of mitochondrial matrix and into intermembrane space

Question 8

What is the role of coenzyme Q and cytochrome c

Answer 8

● Coenzyme Q shuttles e- through complex 1 and 2 (causes transport of 4 H+) to complex III and cytochrome c shuttles e- from complex III to complex IV

Question 9

Why do we need coenzyme Q and cytochrome c

Answer 9

electrons dont dissfuse well through hydrophobic interior of membrane
- COenzyme Q and cytochrome c are lipid soluble and can transport the electrond

Question 10

Do protein complexes accept electrons? Why or why not

Answer 10

• protein compelx doesnt, redox centres w/in protein complex accept electrons

Question 11

What is the function of redox centers, where are they located

Answer 11

-Since protein complexes themselves arent reversible reduced/oxidized, redox centers can be reversible reduced and oxidizes (like Nad+ and NADH)

Question 12

How many redox centers are in a protein complex

Answer 12

Proteins complexes contain a combination of two or more redox centers

Question 13

What are the types redox centers in a protein complexes

Answer 13

○Fe-S clusters
○Copper (Cu)
○Cytochromes
○Coenzymes

Question 14

What happens to the electrons on NADH and FADH (what complexes..)

Answer 14

NADH donates e- to complex I, complex I passes it to complex III then complex IV
FADH2 It donates its e- to complex II (which is logical and convenient since it’s already there anyways). Then complex II passes it along to complex III then complex IV

Question 15

What is FADH2 in cirtric acid cycle

Answer 15

Electron donor but also coenzyme that is prosthetic group that’s covalently bound to enzyme succinate dehydrogenase which is part of complex II

Question 16

What is shutte of electrons driven by

Answer 16

• reduction of potentials of coenzymes and each individual redoc center until final e- acceptor (O2)

Question 17

What is the final reduction

Answer 17

oxygen catalyzed by enzyme cytochrome oxidase making 2 H2O which is part of complex IV

Question 18

What is reduction potential

Answer 18

Affinity something as for e-

Question 19

What is the relative reduction potential of NADH and Oxygen during the beginning of ETC

Answer 19

NADH has lowest reduction potential (least affinity for e-) whereas oxygen has highest reduction potential (highest affinity)

Question 20

What happens to the redox centers between NADH and oxygen

Answer 20

you pass from protein complex I to III to IV they have increasing reduction potential

Question 21

Describe what happens in Complex 1: NADH to Ubiquinone

Answer 21

• NADH transfers 2 e- and 1H+ to complex 1
• Complex 1 uses 2e- to pump 4 H+ from matrix into inter membrane space
• Then the two e- are transfer to Coenzyme Q (QH2)

Question 22

Describe what happens in Complex 2: Succinate to Ubiquinone

Answer 22

• FAD accept two e- from succinate and becomes FADH2
• the electrons from FADH2 pass through iron-sulfur centers to ubiquinone (Coenzyme Q) (QH2)
• IT DOES NOT PUMP PROTEONS
• capture and donates protons

Question 23

Describe what happens in Complex 3: Ubiquinone to Cytochrome C oxidoreductase

Answer 23

• Coenzyme Q’s reduce 2 molecules of cytochrome c
• electrons pass through Iron sulfur clusters, cytochrome b and cytochrome c
• Clearance of e- from reduced Quinones via Q cycle results in 4 H+ to be pumped into inter membrane space

Question 24

Describe Complex 4: Cytochrome C to O2

Answer 24

• Four electrons (From cytochrome c) reduce 1 Molecule of oxygen to 2 molecules of water
• Four protons are picked up from matrix for this process
• ANother 2 H are passed from matrix into inter membrane space

Question 25

What happens each time electrons pass through protein complexes. What is it used for

Answer 25

- each time e- pass through protein complex w/ lower reduction potential to redox centre w/ high reduction potential; energy is released - The complex uses the energy released to drive proton pumping mechanism that pumps proteins out of matrix and into inter membrane space

Question 26

How many Protons does each complex pump out per pair of electrons

Answer 26

●Complex I and III each pump 4 protons for each pair of electrons that pass through and Complex iV pumps out only two protons and Complex II pumps nothing

Question 27

What is the chemiosmotic gradient

Answer 27

The removal of protons from the matrix and deposition of protons in the intermembrane space creates a concentration difference of protons across the inner membrane (chemoosmotic gradient)

Question 28

What is the only way for protons to move to inner mitochondrial membrane

Answer 28

Through specific transport protein

Question 29

What is the gradient in nature

Answer 29

Electrochemical

Question 30

Why is it called electrochemical in nature

Answer 30

○chemical in nature in terms of creating a lower pH of the outside of the inner membrane ○‘electrical’ in natural because of the positive charge of the protons needed to reach equilibrium by entering mitochondrial matrix where charge is negative

Question 31

What does the chemiosmotic gradient able to do

Answer 31

- it has potential energy stored | - energy is used to drive synthesis of ATP by process called oxidative phosphorylation of ADP to ATP in the complex V

Question 32

In What complex does the oxidative phosphoyrlation of ADP occur

Answer 32

ATP, is catalyzed by complex V which is also known as F1-F0 ATP synthase that is composed of multiple subunits

Question 33

Describe the strucutre of Complex V

Answer 33

- aka F1-F0 ATP synthase composed of multiple subunits - F0 subunit: Protein channel that spans inner mitochondrial membrane, responsible for allowing protons to enter matrix. Integral membrane protein. Its energy is transferred to F1 to catalyze phosphorylation - rotates when a new hydrogen ion enters, once three protons/h enter the matrix space, there is enough energy in the ATP synthase complex to synthesize one ATP - F1 subunit: bulbous portion on matrix side of inner membrane. Has the ATP synthase enzyme. Its soluble in maxtrix and individually catalyzes the hydrolysis of ATP. - F1+F0 are connected by protein stalk - looks like mushroom protruding into the matrix on the inside of the inner membrane.

Question 34

How does complex V work?

Answer 34

● One hydrogen ion enters the ATP synthase complex from the intermembrane space a second hydrogen ion leaves it on the matrix space ● Upper part of the ATP synthase complex rotates when a new hydrogen ion enters, once three protons/h enter the matrix space, there is enough energy in the ATP synthase complex to synthesize one ATP ○ Energy in the hydrogen ion gradient is used to make ATP ● Proton enters ATP synthase and exits into the matrix space ● Once three more h atoms have crossed the membrane, ATP is made ● Keeps going until there is an equal number of protons on each side of the inner membrane, no more energy left ● In biological systems, a gradient is always maintained ○ Mitochondrial hydrogen ion gradient is generated as electrons pass through three membrane complexes

Question 35

How is the gradient maintained

Answer 35

Mitochondrial hydrogen ion gradient is generated as electrons pass through three membrane complexes

Question 36

What drives the ATP synthase in F1 subunit

Answer 36

When protons pass through F0 channel and stalk from outside to inside of matrix ○proton serves to drive the molecular motor of the ATP synthase which has an ADP and an inorganic phosphate (Pi) present in the active cell ○Proton actually drives the conformation change in the active site and drives the catalysis of the formation of a new high energy phosphoanhydride bond in ATP

Question 37

How many protons are pumped out as a result of NADH

Answer 37

● Each NADH that donates its electrons to the electron transport chain at complex I, a total of 10 protons are pumped out

Question 38

How many protons are pumped out as a result of FAHD2

Answer 38

● Each FAH2 that donates its electrons through complex II, a total of only 6 protons are pumped out

Question 39

How many ATP can NADH yeild and why

Answer 39

3 ATP (per mole of O2 consumed) due to 10 protons pumped out (Need 3/ATP)

Question 40

How many ATP can FADH2 yield

Answer 40

2 ATP (per mole of O2 consumed) due to 6 protons

Question 41

How many ATP are generated per glucose molecule that is oxidized (and from which processes)

Answer 41

38 ATP | From Glucose to Pyruvate and Pyruvate to Acetyl CoA and then citric acid cycle

Question 42

How does NADH from glycolysis reach the mitochondria Matric

Answer 42

- It never is able to cross into the inner membrane | there is no transport for NADH

Question 43

What are mechanism by which NADH can donate its electrons to transverse into the membrane. Explain them

Answer 43

- Two pathways that provide electrons for NADH generated in the cytosol to ETC: - Glycerol-3-phosphate - Malate aspartate shuttle