Correction — Cell Biology
The Powerhouse With No Power
School diagrams call the mitochondrion the powerhouse of the cell. In one parasite, the mitochondrion has no DNA, 59 proteins, and makes no energy.
A cell contains small working parts called organelles. The mitochondrion is one, and every school diagram labels it the powerhouse of the cell. That sentence is true of most cells. It is false of at least one.
Giardia is a single-celled parasite that lives in the gut of animals and people. Its cells carry tiny organelles that descend from mitochondria. Stand inside one. In a study published on October 1, 2026, researchers counted every protein it holds. A protein is a molecular part, a machine or a girder, built from a written recipe. They found 59.
An ordinary mitochondrion has three marks. It carries its own DNA, the molecule that stores recipes. It makes the cell’s energy. And it holds a great many kinds of protein: over a thousand in a human. This organelle has no DNA, makes no energy, and holds 59. The researchers call it a remnant.
With no DNA, nothing in it is built on the spot. Every one of its 59 proteins is made in the rest of the cell, from recipes kept in the cell’s nucleus, and carried in through the membrane. The organelle is an assembly of imported parts.
In an ordinary mitochondrion, the power comes from hydrogen. Proteins in the membrane pump hydrogen ions, hydrogen atoms stripped of their electrons, to one side. The ions flow back through a protein that turns like a turbine, and the turning makes ATP, the molecule cells spend as energy. In this remnant that function is absent. Nothing is pumped, nothing flows, and no ATP is made here.
Earlier work on Giardia’s version found one job: building iron-sulfur clusters. These are small units of iron and sulfur that enzymes elsewhere in the cell need in order to work. A mitochondrion that makes no power is kept for a parts-making job. The name has outlasted the original work.
Giardia is one of six. The project, called MitoCarta Tree of Life, mapped mitochondrial proteins in a plant, Arabidopsis, and in five single-celled pathogens: Giardia, Acanthamoeba, Babesia, Leishmania and Trypanosoma. The range is wide. Acanthamoeba has the most elaborate energy machinery of the group and can switch between using oxygen and not using it. Leishmania and Trypanosoma carry mitochondrial protein sets 50 percent larger than a human’s.
Several of the parasites share mitochondrial proteins that human mitochondria lack. A protein that the parasite has and a human does not is a possible drug target, a part a medicine could hit without hitting ours. In principle. The researchers list these as potential targets for tropical diseases. Whether any of them yields a drug is a separate and much longer question.
The powerhouse line has exceptions. One parasite’s mitochondrion has no DNA, 59 proteins, and makes no energy. Its parts are all imported, and its one known job is building iron-sulfur parts. A name can outlast the job.