Natural Science (NATS) 1525 Practice Test

The main idea is energy production. Mitochondria generate most of the cell’s ATP through cellular respiration. In this process, nutrients are oxidized to transfer energy onto carrier molecules like NADH and FADH2. Those carriers deliver electrons to the electron transport chain in the inner mitochondrial membrane. As electrons move through the chain, protons are pumped across the membrane, creating a gradient. ATP synthase uses that gradient to convert ADP into ATP, the cell’s main energy currency. Oxygen acts as the final electron acceptor, enabling the efficient production of ATP.

Photosynthesis, which creates sugars from light energy, happens in chloroplasts, not mitochondria. Storing genetic information is done mainly by DNA in the nucleus (mitochondria do contain some mitochondrial DNA, but that’s not their primary role). Protein synthesis occurs primarily on cytoplasmic ribosomes and the rough endoplasmic reticulum; mitochondria can make a few of their own proteins, but this isn’t their main function.