The Electron Transport Chain (ETC): Cellular Respiration Part 4

Final Step!

Where is the electron transport chain located?

Along the inner mitochondrial membrane (cristae).

How are the proteins arranged?

In order of increasing electronegativity (ability to attract electrons).

What reactions occur in the ETC?

Redox reactions (electrons are passed from one protein to another).

The more positive the redox potential value

the more likely it is to gain electrons

The more negative the redox potential value,

the more likely it is to lose electrons

What happens as electrons move through the ETC?

Energy is released at each complex.(stage)

Redox Potential

How strongly a complex wants electrons. The last electron competitor is the most competitive which causes a pullet system.

What is the final electron acceptor?

Oxygen (O₂), which combines with electrons and H⁺ to form water.

Each compound is reduced

by gaining electrons from the compound before it.

How does each compound become oxidized?

By passing its electrons to the next compound.

What happens as electrons move through the ETC?

They become more stable and release free energy.

What is the released energy used for?

To pump protons (H⁺) from the matrix into the intermembrane space.

What type of transport is used to pump H⁺?

Active transport (requires energy).

How many protons are pumped per 2 electrons?

2e⁻ = 1H⁺.

The high energy electron carriers can be used to produce a proton gradient to power ATP synthase.

High energy electrons are “dumped” into the electron transport chain by our electron carriers NADH and FADH2

This energy is used to pump H+ ions from the matrix to the intermembrane space and create an H+ ion gradient. This gradient is used by ATP synthase to make ATP

A lack of oxygen in this system will stall the entire reactive process in the mitochondria (which is already slow) and cause a back up of pyruvate and a lack of NAD+.  This means that more pyruvate will be diverted to femenation until oxygen becomes abundant again.    

Protein Complex 1 (NADH dehydrogenase)

Oxidizes NADH to NAD+, used energy in electrons to pump H+ ions

Protein Complex 2 (succinate dehydrogenase)

Oxidizes FADH2 to FAD

Coenzyme Q (ubiquinone)

Picks up electrons from Protein Complex 1&2 and shuttles them to protein complex 3

Protein Complex 3 (cytochrome b-c)

Uses high energy electrons to pump H+ ions into the intermembrane space

Cytochrome C

Transports electrons to protein complex 4

Protein Complex 4 (cytochrome c oxidase)

Uses high energy electrons to pump H+ ions into the intermembrane space. Electrons are used to react H+ and oxygen gas to make water. Oxygen is referred to as the terminal electron acceptor. This regenerates the water that was split in photosynthesis

ATP Synthase

Uses the energy of the hydrogen ion gradient. H+ ions flow from high to low concentration, and this energy is used by the enzyme to make ATP in the matrix.

Chemiosmosis

Pumping H+ ions into the intermembrane space creates a hydrogen ion (H+) gradient, with a high concentration in the intermembrane space and a low concentration in the mitochondrial matrix.

Leaky Membrane

not holding all the hydrogens, can’t be properly pumped up and will get diffused

NADH bonds at

Protein Complex #1

FADH2 bonds at

Protein Complex #2

Each NADH makes approximately

3 ATP

Each FADH₂ makes approximately

2 ATP

IN TOTAL:

For 1 glucose: 

2 ATP (From Glycolysis)

2 ATP (From Kreb’s Cycle)

10-NADH x 3 ATP = 30 ATP

2-FADH₂ x 2 ATP = 4 ATP

Total ATP: Max 38 ATP (not realistic)

• 6 O2 are consumed, 6 H2O and 6 CO2 are produced