In eukaryotic cells, the electron transport chain is located in the:

• A. outer mitochondrial membrane
• B. cytosol
• C. mitochondrial matrix
• D. inner mitochondrial membrane

Answer: (D)

Verified step by step guidance

1. Understand the structure of a mitochondrion: A mitochondrion has four main regions - the outer mitochondrial membrane, the intermembrane space, the inner mitochondrial membrane, and the mitochondrial matrix.
2. Recall the function of the electron transport chain (ETC): The ETC is a series of protein complexes and electron carriers that transfer electrons to generate a proton gradient, which is used to produce ATP.
3. Identify the location of the ETC: The protein complexes and electron carriers of the ETC are embedded in the inner mitochondrial membrane. This location is crucial because it separates the mitochondrial matrix from the intermembrane space, allowing the establishment of a proton gradient.
4. Eliminate incorrect options: The outer mitochondrial membrane is not involved in the ETC, the cytosol is outside the mitochondrion, and the mitochondrial matrix is where the Krebs cycle occurs but does not house the ETC.
5. Conclude that the correct answer is the inner mitochondrial membrane, as it is the site where the ETC operates to facilitate ATP production.