Exam 2 Lecture #6 (ZIMA)

Question 1

The final step in oxidation of carbs and fatty acids are located in the mitochondria where energy accumulated in _______________.

Mitochondria have two membranes:_________.

These membranes create two seperated spaces:____________.

Answer 1

The final step in oxidation of carbs and fatty acids are located in mitochondria where energy accumulated in NADH and FADH2 is transformed into energy of ATP - “oxidative phosphorylation”

Mitochondria have two membranes: outer and inner membrane (forms cristae)

These membranes create two seperated spaces: intermembrane and matrix

Question 2

What enzymes are within intermembrane space?

Purpose of outer membrane “porin”?

What enzymes are on the inner membrane?

Which enzymes are within the matrix space?

Answer 2

The intermembrane space: kinases involved in transfer of the high energy bond of ATP

The outer membrane: porin (channel for many molecules with MW < 10kDa)

The inner membrane: the most complex membrane (enzymes of ETC, ATPase, and several transporters)

The matrix space: enzymes of TCA cycle and beta oxidation, mtDNA, ribosomes

Question 3

NADH and FADH2 are ______ by the ETC, which is ________

ETC is a sequence of _________ rxns

Potential at which an electron donor gives up its e- to electron acceptor is expressed as the ______

Answer 3

NADH and FADH2 are oxidized by the ETC, a system of e carriers and emzymes (oxidoreductases)

ETC is a sequence of redox rxn’s

(OILRIG)

Potential at which an electron donor gives up its electron to the electron acceptor is expressed as the redox potential

Question 4

Redox couples with a large negative potential will do what vs a more positive redox potential?

Answer 4

More negative equation: will be the one that loses electrons

The more positive redox potential won’t lose electrons

Question 5

How much energy is in one mol of ATP?

Answer 5

48-49 kJ/mol

Question 6

Give an overview of what the ETC does

Answer 6

ETC:

The ETC oxidizes NADH and FADH2 by transferring electrons in several steps to oxygen, while capturing the free energy of the redox rx’s to drive the synthesis of ATP.

During this process, H+ are pumped from the matrix across the inner membrane to form the H+ gradient which provides energy for ATP synthesis.

In the ETC, the electron cacrriers are grouped into four large multisubunit complexes (I-IV)

Question 7

Which molecule has the lowest redox potential (most negative)… vs which molecule has the highest redox potential (most positive)

Answer 7

NADH has the most negative redox potential (it wants to lose electrons, wants to get oxidized)

O2 has the most positive redox potential (it wants to gain electrons, wants to get reduced)

Question 8

Complex I is the most complicated and consists of at least ______

Complex I oxidizes ____ and transfers e- to _____

Explain the Steps

How many total protons are shuttled by complex I

Answer 8

Complex I is the most complicated and consists of at least 40 different polypeptides (1MDa)

Complex I oxidizes NADH and transfers electrons to ubiquinone (coenzyme Q)

Step 1: transfer of 2e- to NADH to cofactor FMN within the complex

Step 2: transfer of 2e- from FMN to Fe-S centers of complex

Step 3: transfer of 2e- from a Fe-S center of the complex to UQ

COMPLEX 1 shuttles 4 H+

Question 9

What is the name of complex I?

Answer 9

Complex I is NADH dehydrogenase

(also uses FMN and Fe-S)

Question 10

What is the name of complex II

Answer 10

Complex II: succinate dehydrogenase

Question 11

Complex II catalyzes oxidation of ____ and consists of ___ subunits.

During oxidation of ____ by Complex II, ___ e- and __ H+ are transfered to _____

The small amount of energy liberated during complex II is ____ for H+ pumping across the membrane

Answer 11

Complex II catalyzes oxidiation of succinate and consists of four subunits (one contains FAD, another contains Fe-S)

During oxidation of succinate by Complex II, 2 e- and 2H+ are transferred to FAD, creating FADH2

The small amount of energy liberated during the oxidation of succinate is insufficient for H+ pumping across the membrane.

Question 12

Which complex does NOT pump any H+ across the membrane?

Answer 12

Complex II doesn’t pump any protons

Question 13

What is the name of complex II

Answer 13

Complex II: succinate dehydrogenase

Question 14

What is the name of complex III

Answer 14

Complex III: cytochrome bc1

Question 15

Complex III catalyzes transfer of e- from ___ to _____, and pumps ___ across the inner membrane

Complex III consists of ______ subunits, including how many alpha helixes?

Answer 15

Complex III catalyzes transfer of electrons from UQ to cytochrome c coupled to the translocation of 4 H+ across the inner membrane.

Complex III consists of 11 subunits containing eight alpha helixes?

Question 16

Cytochrome c contain _________ group

In ETC, there are three classess of cytochrome c(______)

From complex III, electrons are transfered to____

Cytochrome c is a small/large globular protein that is hydrophobic/hydrophillic with a ___ group.

Cytochrome c functions as a ______ in the ETC

Answer 16

Cytochrome c contain Fe- containing heme group

In ETC there are three classes of cytochrome c: a, b, and c

From Complex III, electrons are transferred to cytochrome c

Cytochrome c is a small globular hydrophillic protein with a heme group

Cytochrome c (like Uq) functions as a mobile e- carrier in the ETC

Question 17

What is the name of Complex IV?

Answer 17

Complex IV: cytochrome c oxidase

Question 18

Complex IV catalyzes transfer of e- from ___ to ____

Complex IV consists of ____ subunits and contains as redox components_____ and ______

Answer 18

Complex IV: catalyzes transfer of electrons from cytochrome c to O2 (which is the terminal electron acceptor) to form H20 coupled to the translocation of H+ across the inner membrane.

Complex 4 consists of 13 subunits and contains as redox components: two cytochrome and two copper centers

Question 19

Transfer of e- through Complex IV:

Step 1:

Step 2:

Step 3:

Answer 19

Complex IV:

Step 1: electrons are transferred from cytochrome c to the Cua site on subunit II

Step 2: then e- are transferred to heme a in subunit 1

Step 3: e- are moved to the Cub and heme a3 redox center, where the final transfer of e- to O2 occurs

The transfer of 2 e- through complex IV is associated with the uptake of 2 H+ from matrix

Question 20

Explain how the ETC and proton pumping are related

What does that do to the two sides of the membrane?

Which side becomes more acidic, which side becomes more alkaline?

Answer 20

The energy released during the electron transfer through the ETC is used to pump H+ across the inner membrane (H+ gradient). This creates a difference in H+ concentration on the two sides of the membrane. The intermembrane space becomes more acidic and the matrix becomes more alkaline.

Question 21

How many protons are pumped across in total by the ETC?

What is the free energy available from this process?

Answer 21

During the transfer of 2 e- from NADH to O2 approximately 10 protons are pumped across the membrane to establish the electrochemical gradient.

The free energy available from this process DELTAG= -219 kJ/mol (enough energy to produce 3 ATP)

Question 22

How many protons are pumped in each complex?

Answer 22

Protons Pumped in the ETC:

Complex I: 4 H+

Complex II: 0

Complex 3: 4 H+

Complex 4: 2 H+

Question 23

The need for ATP in a cell regulates _____

ADP does what to the rate of ATP synthesis and thus 02 consumption rate

Answer 23

The need for ATP in a cell (energy demand) regulates the rate of ATP synthesis in mitochondria, which in turn regulates the rate of the ETC.

ADP increases the rate of ATP synthesis and flux of e- through the ETC, thus leading to a higher rate of O2 consumption

THUS, rate of electron transport is tightly coupled to ATP synthesis

Question 24

Explain what oligomycin does

Explain what protonophores (DNF, FCCP, and CCCP) do

Answer 24

Oligomycin is an inhibitor of ATP synthase, preventing the movement of H+ through ATP synthase. This will slow the electron flux via the ETC and thus the rate of O2 consumption

Protonophores will uncouple the electron transport through the ETC and ATP synthesis… in the presence of protonophores, electron transport many continue but without ATP synthesis

Question 25

ATP Synthase:

What does ATP Synthase do?

Explain the F1 and Fo domains

Answer 25

ATP Synthase (complex V) catalyzes ATP production using the energy of the proton gradient

F1 domain catalyzes the binding sites for ATP and ADP and catalyzes ATP synthesis

Fo domain provides channel for H+ movement

Question 26

Mitochondrial ROS formation

Answer 26

O2- is generated at complex I and complex III

O2- is not permeable but can pass through ion channels

o2- is then turned into H2O2 in the matrix