Wize AP Biology Textbook > Cellular Respiration

The Electron Transport Chain [detailed]

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The Electron Transport Chain
Glycolysis, pyruvate processing, and the citric acid cycle transferred energy from glucose to 10 NADH and 2 FADH2 and produced 4 ATP by substrate level phosphorylation.
The electron carriers NADH and FADH2 are then used to produce more ATP by oxidative phosphorylation by transferring electrons to the electron transport chain.
The electron transport chain consists of a series of 4 transmembrane complexes and a transmembrane ATP synthase.
The energy from NADH and FADH2 is used to transport H+ ions across the membrane to generate an electrochemical gradient.

The electron transport chain can be broken down into the following steps:

NADH transfers electrons to complex I, which transports 4 H+ across the membrane. The 4 electrons (e-) are transported by coenzyme Q (CoQ) to complex III.

FADH2 transfers electrons to complex II. The electrons (e-) are transported by coenzyme Q (CoQ) to complex III. (NOTE: no H+ are transported by complex II).
Complex III transfers electrons to complex IV through cytochrome C. Complex III transports 4 H+ across the membrane.



Complex IV transfers electrons to reduce ½ O2 to H2O. Complex IV transports 2 H+ across the membrane.
The electrochemical gradient that was generated in steps 1 through 4 is used to synthesize ATP. H+ ions flow through ATP synthase to produce ATP from ADP and Pi. This is called oxidative phosphorylation.

ATP YIELD: 30 - 32 ATP per glucose (Note: 2 ATP from glycolysis + 2 from TCA cycle)
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Summary

Photo by RegisFrey / CC BY

How much ATP is produced from the oxidation of 1 molecule of glucose?

(10H+/NADH)x(1ATP/4H+)=2.5ATPperNADH(10H^+/NADH)x(1ATP/4H^+)=2.5ATPperNADH(10H+/NADH)x(1ATP/4H+)=2.5ATPperNADH

(6H+/FADH2)x(1ATP/4H+)=1.5ATPperFADH2(6H^+/FADH_2)x(1ATP/4H^+)=1.5ATPperFADH_2(6H+/FADH2​)x(1ATP/4H+)=1.5ATPperFADH2​

Practice: Complexes of ETC
Which complex in the electron transport system initially accepts electrons from FADH2?

Practice: Names of Complexes
Match the full name to the ETC complex. (Even though not specified in the video lesson, the names match function)

A.

Cytochrome c oxidase

B.

NADH-Q reductase complex

C.

Succinate/Q reductase

D.

Ubiquinol/cytochrome c oxidoreductase

Complex I

Complex II

Complex III

Complex IV

I don't know

Practice: H+ Gradient
Which of the following is FALSE regarding the H+ gradient?

A) Protomotive force of H+ ions entering the mitochondrial matrix drives ATP synthesis.

B) H+ ions cause a conformational change in ATP synthase as they flow into the matrix.

C) The gradient is created by H+ ions being pumped out of the matrix due to multiple oxidative phosphorylation reactions.

D) The outer surface of the inner mitochondrial membrane will be charged. 

E) The pHmatrix > pHintermembrane before ATP synthesis occurs.

I don't know

Practice: Cascade of Electrons
How do electrons cascade down the electron transport chain (ETC)?

A) With the current generated by proton (H+) pumps 

B) Against the current generated by proton (H+) pumps 

C) By subsequently passing from a carrier with a higher affinity to one with a lower affinity for electrons

D) By subsequently passing from a carrier with a lower affinity to one with a higher affinity for electrons

E) O2 draws electrons down the chain

I don't know