Suppose a bacterium was exposed to a chemical that poisoned its cytochrome oxidase. Which of the following transport processes would be affected first? Choose one: A. the lactose symporter (LacY) B. facilitated diffusion C. the phosphotransferase system D. sodium antiporters E. ABC transporters

The lactose symporter (LacY).

Explanation:

The cytochrome oxidase is the protein present in the prokaryotes as well as eukaryotes. This oxidase is one of the most important component of electron transport chain in eukaryotes.

The lactose symporter is responsible for the transportation of lactose and the hydrogen ions in the bacterial cell. The poison that affects the cytochrome oxidase will affects the proton movement and disrupt the proton motive force that affects the LacY symporters.

Thus, the correct answer is option (A).

lactose symporter

Explanation:

Lactose symporter facilitates the entry of lactose and protons in the bacterial cells. This generates the proton concentration gradient in the bacterial cells with the inside of the bacteria having higher concentrations of protons. The proton concentration gradient is harnessed by the electron transport chain to facilitate ATP synthesis.

Cytochrome oxidase is complex IV and serves to transport the electrons to molecular oxygen. It also actively pumps protons back to the exterior. Cells with poisoned cytochrome oxidase would not be able to pump the protons and lactose symporter would not be able to symport protons and lactose in the absence of proton concentration gradient.