Mitochondria: Powerhouses of the Cell

Andy and Marco chat on the Internet about being able to eat ice cream and still lose weight. They talk about sugar and fat metabolism and about being hot. They “sweat rivers.” Both take the diet drug DNP [Dinitrophenol]. They want to “get the best dosing schedule for using DNP to get the most fats nailed down.” What they don't talk about are the risks they're taking with their mitochondria.

In Latin, mitochondria means “threadlike granules.” Much evidence suggests that they are the descendents of ancient bacteria. Most of our energy comes from chemical reactions that occur within mitochondria. Our cells have hundreds of them, depending on how much energy the cells need. Mitochondria convert the energy of foods into ATP (adenosine tri-phosphate). ATP is the biological equivalent of cold, hard cash—available energy. Let's look at how efficiently mitochondria make ATP.

Many chemical reactions involve the transfer of hydrogen, which is made of a proton and an electron. In the inner membrane of mitochondria, electrons are transferred from one molecule to another, with oxygen being the last acceptor. At the same time, protons are pumped across the membrane (from the inside to the outside). Those protons, simply by being on the other side of the membrane, have energy stored in them, like water on top of a hill. But the protons are not free to come back inside, because the membrane is a barrier.

We extract energy from falling water with turbines to get hydroelectric power. In the same way, a special channel captures the energy of the protons to make ATP by allowing the protons to flow back inside through the channel.

When Andy and Marco take DNP, they destroy the mechanism for making ATP. DNP binds to protons and travels across the inner membrane freely (because it can), releasing protons inside. Those protons never go through the special channel, so ATP isn't made. It's like falling water that never goes through the turbine, resulting in no electricity.

Mitochondria keep pumping protons out. But it's a futile cycle. Food molecules are used up and no usable energy is captured from it. The energy is released as heat instead.

Normally, reactions are tightly coupled so that electrons do not flow from food molecules to oxygen unless cells need ATP. With DNP, the reactions proceed uncontrolled, resulting in weight loss and heat.

Andy and Marco are lucky. They haven't ended up in the hospital yet. But others weren't so lucky. They died trying to get thin fast.

Vocabulary

metabolism:
The process by which living things change food into energy and living tissue.

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Activity

  1. What is ATP? What function does it perform?
    Answer: ATP is adenosine tri-phosphate, a substance made by the mitochondria. It provides energy for cells.
  2. What role do protons play in the process of metabolism?
    Answer: In metabolism, protons are separated from their atoms or molecules and passed across the membrane of a mitochondria. When the proton re-enters the mitochondria through a special channel, it releases energy, which is used to make ATP.
  3. What does DNP do? What effect does this have?
    Answer: DNP prevents protons from going through the special channel as it is re-entering the mitochondria. Since the protons do not go through the special channel, the mitochondria cannot capture energy from the protons.
  4. Why is DNP harmful?
    Answer: DNP is harmful because it prevents the mitochondria from capturing the energy from protons to make ATP. If this occurs too often, a lot of heat is released, which raises the temperature of the body.

Activity

  1. What is ATP? What function does it perform?
    Answer: ATP is adenosine tri-phosphate, a substance made by the mitochondria. It provides energy for cells.
  2. What role do protons play in the process of metabolism?
    Answer: In metabolism, protons are separated from their atoms or molecules and passed across the membrane of a mitochondria. When the proton re-enters the mitochondria through a special channel, it releases energy, which is used to make ATP.
  3. What does DNP do? What effect does this have?
    Answer: DNP prevents protons from going through the special channel as it is re-entering the mitochondria. Since the protons do not go through the special channel, the mitochondria cannot capture energy from the protons.
  4. Why is DNP harmful?
    Answer: DNP is harmful because it prevents the mitochondria from capturing the energy from protons to make ATP. If this occurs too often, a lot of heat is released, which raises the temperature of the body.