Detailed Study Guide on the Electron Transport Chain for Biology Course

The electron transport chain will pass electrons from NADH/FADH2 to ___

oxygen

How many electrons does it take to fully reduce a molecule of oxygen?

4 electrons (2 pairs)

What is the reaction for the reduction of oxygen?

2e- + 1/2 O2 + 2H+ --> H2O

NADH and FADH2 are reoxidized by:

carriers in the electron transport chain

Where are the electron transport chain proteins embedded?

inner mitochondrial membrane

The inner mitochondrial membrane is folded into structures called:

cristae

The inner mitochondrial membrane is highly _____ to most outside particles

impermeable

70% of the inner mitochondrial membrane is composed of ______, while 30% is composed of _____

protein; lipid

The outer/inner mitochondrial membrane is separated by the ___ ___

intermembrane space

What is the fluid-filled space INSIDE the inner mitochondrial membrane?

mitochondrial matrix

Where does the citrate cycle take place?

mitochondrial matrix

The operation of the electron transport chain will create an ____ ____

electrochemical gradient

NADH and FADH2 are found within the

mitochondrial matrix

When NADH is oxidized to NAD+, H+ is pumped from the _______ to the ______

matrix --> intermembrane space

When H+ is pumped from the matrix to the intermembrane space, there is a large potential energy within the intermembrane space, known as:

proton-motive force

When protons flow down their gradient into the matrix, they must pass through

ATP synthase

When protons flow down their gradient into the matrix, the negative ΔG reaction will power:

ATP synthesis

The oxidation of NADH/FADH2 will phosphorylate ADP to produce ATP.

This reaction is known as

oxidative phosphorylation

The transfer of electrons between carriers in the electron transport chain are all -ΔG reactions.

These reactions will drive:

the pumping of H+ against their gradient into the intermembrane space

The electron transport chain is also known as the ____ ___

respiratory chain

The electron transport chain is composed of _____ large multiprotein complexes

4

The 4 large multiprotein complexes of the ETC are embedded within the

inner mitochondrial membrane

In addition to the four large protein complexes. there are 2 ___ ____ that shuttle between complexes

mobile carriers

What are the electron carriers in the ETC?

Coenzyme Q and Cytochrome C

What electron carrier shuttles from Complex I/Complex II to Complex III?

Conenzyme Q

What electron carrier shuttles from Complex III to Complex IV?

Cytochrome C

Each of the components in the ETC has increasing ___ ___

reduction potential

What are the two flavoproteins in the ETC?

1. Flavin mononucleotide (FMN)

2. Flavin Adenine Dinucleotide (FAD)

FAD will enter the electron transport chain in: (FAD--->FAD2H)

Complex II

NADH will enter the electron transport chain in: (NADH ---> NAD+)

Complex I

Coenzyme Q is also called:

ubiquinone

Coenzyme Q is _____, and as a result, can diffuse within the inner mitochondrial membrane

hydrophobic

Cytochrome C is a soluble carrier that is associated with the ______ _____ of the inner mitochondrial membrane

outer surface

The energy generated during the transfer of electrons isn't used to DIRECTLY synthesize ______ , but is used to pump protons against their gradient

ATP

The driving force for protons to go into the mitochondrial matrix is known as:

proton-motive force

Complex I (NADH-Q Oxidoreductase) catalyzes:

1. oxidation of NADH

2. reduction of coenzyme Q

Complex II (Succinate-Q reductase) catalyzes:

1. oxidation of succinate

2. reduction of Coenzyme Q

Complex III (Q-cytochrome C oxidoreductase) catalyzes:

1. oxidation of coenzyme Q

2. reduction of cytochrome C

Complex IV (cytochrome C oxidase) catalyzes:

1. oxidation of cytochrome C

2. reduction of oxidase

Which complexes transfer protons into the intermembrane space?

Complex I, III, IV

Which complexes DO NOT transfer protons into the intermembrane space?

Complex II

After NADH is reduced, the electrons are passed from Complex I to _____

Complex III

How many protons does Complex I pump into the intermembrane space?

4H+

How many protons does Complex III pump into the intermembrane space?

2H+

How many protons does Complex IV pump into the intermembrane space?

2H+

Inner mitochondrial membranes are impermeable to _____, so there must be a "shuttle" that will bring its electrons into the matrix

NADH

To get electrons from NADH into the matrix, muscle cells use

glycerol-3-phosphate (G3-P) shuttle

The electrons on FADH2 are picked up by:

Coenzyme Q

In liver cells, electrons will be transferred from NADH onto _____ via ____

oxaloacetate; malate dehydrogenase

When oxaloacetate receives electrons from NADH, it will now be converted into

malate

When malate is transported into the matrix, it will enter the ___ ___, and will generate ____

TCA cycle; NADH

In the liver, electrons from NADH will enter the electron transport chain at

Complex I

Why does FADH2 yield less ATP than NADH?

FADH2 electrons enter the electron transport chain at Complex II, which does NOT pump protons into the intermembrane space

ATP synthase is also known as

F1/F0-ATPase

The F1 component of ATP synthase is found in the ____ ____

mitochondrial matrix

The F0 component of ATP synthase is found in the

inner mitochondrial membrane

The F1 component of ATP synthase (matrix component) contains ____ _____ activity

ATP synthesizing

The F0 component is largely _____, and is ______

hydrophobic; membrane-spanning

The F1 subunit is considered the _____ channel

catalytic

The F0 subunit is considered the _____ channel

proton-conducting

Each beta subunit in the hexameric ring (F1) will interact with a distinct surface of the ____ ____

gamma stalk

What determines which conformation each beta subunit will be in?

its interaction with the gamma stalk

What drives the rotation of the gamma stalk?

the transport of H+ from the intermembrane space into the matrix

The synthesis of 1 ATP molecule requires how many protons to be transferred into the matrix via ATP synthase?

3 H+

IN TOTAL, how many protons are required to synthesize 1 ATP molecule (ATP synthase AND Pi translocase)?

4 H+

Per NADH, how many protons are pumped into the intermembrane space?

10 H+

Per FADH2, how many protons are pumped into the intermembrane space?

6 H+

6/4 = 1.5 ATP per FADH2

Under aerobic conditions, how much ATP is generated per glucose molecule?

30 ATP

ATP synthesis is ____ ____ to the inward flow of H+

tightly coupled

1. ATP is not synthesizes unless H+ flows into the matrix

2. H+ does not flow into the matrix unless ATP is being synthesized

Under low activity levels, NAD+ is produced in LOW LEVELS and the citrate cycle will be ______

inhibited

The outer mitochondrial membrane is _____ to most small molecules via porins

permeable; non-selective

The inner mitochondrial membrane is _____ to most small molecules

impermeable

[Complex 1] NADH Ubiquinone Oxidoreductase

contain prostatic groups: (they help passing e⁻)

1. FMN - Flavin mononucleotide

2. Fe-S clusters (Iron-sulfur clusters)

This complex catalyzes:

1. transfer of e⁻ from NADH -> FMN -> Fe-S clusters -> UQ**

** ubiquinone

2. pump 4H⁺ ions, from the matrix to intermembrane space.

net:

NADH+H⁺+UQ+4H⁺(in Matrix) --> NAD⁺+UQH₂+4H⁺(in InterMembranous space)

[Complex 2] succinate dehydrogenase

contain prostatic groups:

1. FAD

2. Fe-S clusters (Iron-sulfur clusters)

3. Heme - doesn't transfer e⁻ but it suppress e⁻ leakage from complex II, which can result in the formation of oxygen radicals.

consists of two parts:

1. succinate dehydrogenase - participate in Kreb's cycle, oxidize Succinate to Fumarate & release e⁻ into complex II.

2. this part consists of FAD₂ & UQ, which recieve e⁻ from part 1 of complex II.

[Complex 3] ubiquinone-cytochrome c oxidoreductase

* This complex is a dimer that transfer e⁻ from reduced UQ to cytochrome C (Cyt C), while using the energy to pump 2H⁺ ions into the intermembranous membrane.

contain prostatic groups & e⁻ carrying molecules:

1. Fe-S clusters (Iron-sulfur clusters)

2. Heme

3. cytochromes (cyt B(l)/B(h)/C₁/C)

passage of e⁻ reffered as two cycles:

* first cycle:

1st UQH₂ enter the complex and transfer one e⁻ to Fe-S clusters -> Cyt C₁ -> Cyt C.

While pumping 2 protons into intermembranous space.

UQH₂ become UQ⁻.

UQ⁻ transfers its second e⁻ to Cyt B₁ -> Cyt B₂.

after releasing the second e⁻, UQ⁻ transformed to UQ and leave into the inner membrane.

* second cycle:

2nd UQH₂ enter the complex and trasnfer one e⁻ to Fe-S clusters -> Cyt C₁ -> Cyt C.

While pumping 2 protons into intermembranous space.

UQH₂ become UQ⁻.

UQ⁻ pickup the e⁻ from Cyt B₂ & 2H⁺ from the matrix to become UQH₂, then it leaves the complex into inetermembranous space.

Note:

UQH₂ = dihydroubiquinone

UQ- = ubisemiquinone

UQ = ubiquinone

[Complex 4] cytochrome oxidase

contain prostatic groups & subunits:

1. Cu(a) & Cu(B) - Cupper ions.

2. Cyt C(a) & Cyt C(a3)

this complex catalyze:

* catalyze the electrons reduction of O₂ to H₂O.

(to form H₂O, 4H⁺ from matrix are used)

* 1 H⁺ (for 1 Cyt C) ion are shuttled through complex 4, so overall 4H⁺ whill be shuttle.

* note - overall complex IV use 8H⁺ from matrix, 4 for forming H₂O and 4 are shuttled to intermembran space.

* e⁻ pass from:

Cyt C -> Cu(a) -> Cyt C(a) -> Cyt C(a3) -> Cu(B) -(Finally to)->O₂

regulation!!!!!

there is ATP-binding regulatory sites on Cyt C & complex IV.

↑[ATP] => decrease in electron transport activity.

Net reaction of the ETC from NADH--> O₂

NADH+H⁺+½O₂+10H⁺(in Matrix) --> NAD⁺+H₂O+10H⁺(in intermembranous space)

what ion passes through F0 component

H+

the component that rotate

gamma spindle

the function of the alpha and beta head

to bind ADP and Pi tightly to synthesis ATP

why when a molecule of FAD2H is processed it generates two ATP molecules while a molecules of NAD2H will generate three ATP

1. NADH transfers electrons to complex I

2. FAD.2H is a reduced coenzyme that transfers electrons to complex II;

3. NADH can only carry one Hydrogen atom whereas FAD.2H can carry two;

4. Therefore FAD.2H can pass more electrons through the electron transport chain which are ultimately used to generate energy in the form of ATP;

similarity and difference between complex I and ubiquinone

Similarity -

protein carrier / transfers electrons;

Difference -

Complex I is a transmembrane protein whereas ubiquinone is a mobile carrier;

where can find the diagram

mitochondria (across the inner mitochondria membrane), oxidative phosphorylation involved