Cytochrome oxidase contains

**Core Concept**
Cytochrome oxidase is a crucial enzyme in the mitochondrial electron transport chain, responsible for transferring electrons from cytochrome c to oxygen, ultimately producing water. This process generates a proton gradient that drives ATP synthesis. The enzyme consists of multiple subunits, including heme groups that facilitate electron transfer.

**Why the Correct Answer is Right**
The correct answer is related to the heme groups present in cytochrome oxidase. The enzyme contains heme a and heme a3, which are essential for the transfer of electrons from cytochrome c to oxygen. The heme groups are located in the enzyme's catalytic subunit and play a critical role in the binding and transfer of electrons. The presence of these heme groups is essential for the enzyme's function in the electron transport chain.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to cytochrome oxidase. Instead, it's related to another enzyme in the electron transport chain, cytochrome b-c1 complex.
**Option B:** This option is also incorrect. The F1F0-ATP synthase is an enzyme responsible for generating ATP from the proton gradient, but it's not a component of cytochrome oxidase.
**Option C:** This option is incorrect as well. The cytochrome c oxidase is not a subunit of the cytochrome b-c1 complex, but rather a separate enzyme in the electron transport chain.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that cytochrome oxidase is a key enzyme in the electron transport chain, and its dysfunction can lead to mitochondrial myopathies and other disorders. The enzyme's heme groups are critical for its function, and mutations in the genes encoding these subunits can result in severe respiratory chain defects.

**Correct Answer:** C.