Electron Transport Chain: Mitochondria

Electron Transport Chain: Mitochondria

By Rose Marsh

Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping

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Electron Transport Chain

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The Third Stage of aerobic respiration is the Electron Transport Chain, which is located on the inner cristae of the mitochondria.

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The Third Stage of AEROBIC respiration

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The inner membrane is arranged into folds cristae, which increases the surface area available for the transport chain

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The Third Stage of AEROBIC respiration

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The hydrogen carriers (NADH and FADH2) are moving along and release high energy electrons and protons

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The electrons are transferred to the electron transport chain, which consists of several transmembrane carrier I proteins

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Step 1: Generating a Proton Motive Force

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As electrons pass through the chain, they lose energy – which is used by the chain to pump protons (H+ ions) from the matrix

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The accumulation of H+ ions within the intermembrane space creates an electrochemical gradient (or a proton motive force)​

Step 1: Generating a Proton Motive Force

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• Highlight the electrons and the Hydrogen Ions!

The proton motive force will cause H+ ions to move down their electrochemical gradient and diffuse back into the matrix

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(high to low concentration)​

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Step 2: ATP Synthesis via Chemiosmosis

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• Highlight the electrons and the Hydrogen Ions!

This diffusion of protons is called chemiosmosis and is facilitated by the transmembrane enzyme ATP synthase

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As the H+ ions move through ATP synthase they trigger the molecular rotation of the enzyme, synthesizing ATP

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Step 2: ATP Synthesis via Chemiosmosis

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In order for the electron transport chain to continue functioning, the de-energised electrons must be removed

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Oxygen acts as the final electron acceptor, removing the de-energised electrons to prevent the chain from becoming blocked

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Step Three: Reduction of Oxygen

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Oxygen also binds with free protons in the matrix to form water – removing matrix protons maintains the hydrogen gradient

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In the absence of oxygen, hydrogen carriers cannot transfer energized electrons to the chain, and ATP production is halted

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Step Three: Reduction of Oxygen

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Multiple Choice

In what part of the mitchondria does the electron transport chain occur?

• Inner mitochondrial membrane (folds of the mitochondria)

• Outer mitochondrial membrane

• Cytoplasm

• Ribosomes

Multiple Choice

The process that enables ATP synthase to function is...

• endocytosis

• active transport

• pinocytosis

• osmosis

• diffusion

Multiple Choice

True or False: Water is produced as a byproduct during this stage of cellular respiration.

• True

• False

Multiple Choice

What does FADH2 and NADH bring to the electron transport chain?

• Oxygen

• Water

• Electron

• ATP

Multiple Choice

ATP synthesis by ATP synthase is driven by

• H⁺ movement

• electron movement

• NADH movement

• FADH₂ movement

Multiple Choice

What enzyme in the ETC is responsible for generating the ATP molecules?

• ATPase
• ATP synthase
• Hexokinase
• none of the above

Multiple Choice

When protons are pumped outside the matrix, across the inner membrane...

• water is made

• a concentration gradient of H⁺ ions (protons) is created

• NADH gets reduced

• CO₂ is produced