(also called Electron Transport Chain or Oxidative Phosphorylation)

At this point, one molecule of glucose has yielded:

The cell has also captured many energetic electrons in electron carrier molecules:
In this 3rd stage of energy production, these electron carriers give up their ____________________ to a highly organized transport system called the Electron Transport System (ETS). The reactions which occur along the ETS drive the synthesis of many ATP!

Steps of The ETS
  1. The ETS consists of a series of molecules (many are proteins) which are embedded in the ______________ _______________ (or ___________) or the mitochondrion. The ETS accepts the ____________________ from the electron carriers and passes them from one "carrier molecule" of the ETS to the next in a series of successive ____________________ and ____________________ reactions.

  2. An NADH gives it's _______________ to the first carrier molecule of the ETS (located at the beginning of the chain) and the electrons begin to travel down the ETS from one carrier to the next.

  3. As the ______________ are passed down the ETS, they release ___________.

  4. The energy is used to pump ____________________ ions (____) from the ____________________ of the mitochondrion, across the ______________ mitochondrial membrane, into the ____________________ compartment.

  5. A ________ concentration of H+ builds up (_____ pH) in the __________________ compartment resulting in a high ____________________ gradient for H+.

  6. These H+ then flow back across the inner membrane into the ____________________ down their _________________ gradient by _________________ diffusion. They do so through special _______________ ion channels or pores called ___________________ assemblies. The pores contain an ATP-synthesizing enzyme (called _______ __________________) so that as the H+ flow through the channels, Pi (____________________ ____________________) is joined to ADP to produce ___________.

  7. Every time an NADH drops off _________________ at the beginning of the ETS and the electrons move down the chain, enough _______________ is released to pump H+ (from matrix to intermembrane compartment) at ___________ spots. And everytime the H+ re-enters the ______________, one ATP is made. Therefore, every NADH dropping off electrons can produce ________ ATP!

  8. Unlike NADH, _______________ misses the beginning of the ETS. It drops its electrons off further down the chain so that H+ can only be pumped out at _________ sites. Therefore, every FADH2 dropping off electrons can produce _________ ATP!

  9. The ATP generated is thus made in the ____________________ of the mitochondrion.

  10. When the ________________ (from NADH and FADH2) reach the last carrier of the ETS (called _______________ _________________), they have lost their ______________. They are then combined with ____________________ (that diffused into the matrix) and ___________________ ions to form _________________.

    Because ___________________ is the last molecule to accept the electrons, it is called the "_________________ __________________ acceptor". The transfer of electrons to oxygen removes them from the ETS chain and allows more electrons to flow down the chain (ie. it prevents a pile-up of electrons). Thus, the ETS can continue to function making more ATP. This is why you must breathe!

    CYANIDE, a potent poison, kills by blocking the final step of electron transport to oxygen. Cyanide binds irreversibly to "cytochrome oxidase" (the last electron carrier complex); the lethal effect is extremely rapid and opportunities for treatment hardly exist; death usually occurs suddenly with terminal convulsions.

What about the NADH from Glycolysis?

The NADH from Glycolysis are produced in the _________________________ of the cell. To get into the mitochondrion for use in the ETS, the __________________ are passed (in SOME cells) through the outer mitochondrial membrane to ____________ producing _____________. Because _________________ has been formed, those electrons only lead to production of ______ ATP. In OTHER cells, the NADH from Glycolysis pass electrons into the mitochondrion to ___________ producing ___________. Because ____________ has been formed, those electrons lead to production of ________ ATP.

Summary of Products from Complete Aerobic Cellular Respiration of One Glucose

Matrix Rxns822
ETS002 NADH (Glycolysis) x 2 ATP/NADH = 4 ATP
8 NADH (Matrix) x 3 ATP/NADH = 24 ATP
2 FADH2 (Matrix) x 2 ATP/FADH2 = 4 ATP


2 NADH (Glycolysis) x 3 ATP/NADH = 6 ATP
8 NADH (Matrix) x 3 ATP/NADH = 24 ATP
2 FADH2 (Matrix) x 2 ATP/FADH2 = 4 ATP

A TOTAL of ___________ or _____________ ATP can be produced from one glucose molecule depending on the type of cell/tissue.

You now know why the mitochondrion is nicknamed the "_______________________ of the cell".