Eli5 What is the process of generating ATP?


Please help, I’m an a level student and this topic doesn’t make sense to me.

I understand that APT is generated differently in plants and animals, but there’s also bactera and other organism that use ATP so would there be a more simple and efficient way to describe and classify how each kingdom generate atp?

Also I kind of don’t understand the process of how it’s done. Does anyone have a non-wordy linear explanation of what exactly happens??

In: 0

The majority of atp, in both plants and animals, is produced in the Mitochondria. Hence the joke on the internet that the thing everyone learns from biology is that “the Mitochondria is the powerhouse of the cell”.

The mitochondria does the majority of breaking down things like sugars to produce ATP.

In the Mitochondria there is a protein Called ATP Synthase, which synthesizes, or makes, ATP. This protein is embedded in the membrane of the Mitochondria, and part of a larger cycle that I learnt as the “Electron Transport Chain”. Though I am sure that there is a more scientific name for it.

I really don’t know what else to put without it getting really into the nitty gritty, but here is a great video on this topic.


You can think of an ATP molecule a bit like a charged battery. The cell is full of them, and anywhere that a bit of energy is needed to carry out some function, the nearest ATP molecule can be grabbed and consumed. Consuming an ATP means breaking off its outermost phosphate group, creating a molecule of ADP. So ADP molecules are kind of like *un*charged batteries, that can be “recharged” by grabbing a free phosphate group and sticking it back on.

When we talk about ATP being generated, this is usually what we’re talking about: a cell taking in energy and using that energy to “recharge” ATD molecules into ATP, replenishing the cell’s overall stores of ATP. And in both plants and animals, *most* of this is done by a highly complex enzyme called [ATP synthase](https://en.wikipedia.org/wiki/ATP_synthase).

ATP synthase is an *amazing* little machine. It’s basically a turbine, that sits embedded in a membrane. Instead of being powered by water pressure, it’s powered by proton pressure — in other words, an excess of H+, hydrogen ions, which are just free protons. A higher proton pressure on one side will push protons through a tunnel in the middle of the protein complex, making the turbine spin. Below this sits three tiny “chambers”, which alternately contract and expand as the turbine rotates. When a chamber opens, an ADP molecule and a phosphate group can enter. As the chamber closes, the ADP and the phosphate group are clicked together, making ATP. As the chamber opens again, the ATP molecule exits. There are animations of how this works in the Wikipedia article I linked to above.

ATP synthase is found in all kingdoms of life, and works pretty much the same in all of them, but its location in the cell and the contexts in which it is used can be a bit different. In bacteria, it sits in the membrane of the cell. In both plants and animals, it sits in the inner membrane of the mitochondria. The energy released when mitochondria break down carbohydrates is used to pump protons from one part of the mitochondria to another, which creates the proton pressure that then powers the ATP synthases.

In plants you *also* find ATP synthases in the chloroplasts. Here, the light energy captured by the chloroplast is used to power the proton pumps that set up the proton pressure difference between one part of the chloroplast and another — but once this proton pressure has been created, it powers ATP synthase just the same as in the mitochondrion. And then this ATP is used by a different part of the chloroplast to capture CO2 and turn it into sugar. So plants make ATP “twice”: first in the chloroplast, then that ATP is consumed to power the making of sugar, then that sugar is consumed as needed by the plant’s mitochondria, making ATP again for the rest of the cell to use.

All living things respire, which is producing ATP from Glucose. In lower organisms like bacteria this is just done in the cell somewhere, while in higher organisms most of it is produced in the Mitochondria.

There is anaerobic respiration, i.e. fermentation, where ATP is generated without Oxygen. This is much less efficient than aerobic respiration, which uses oxygen to produce much more ATP per Glucose molecule. Most aerobic-respirating creatures, including us, can do both depending on the situation, though aerobic respiration is preferrable for obvious reasons. When you sprint, for example, you can’t get enough oxygen to your muscles to maintain that level of activity, so your cells also ferment glucose to get extra ATP out and sprint a little longer.

Plants use photosynthesis to produce their own Glucose from CO2 and sunlight. That glucose then goes toward respiring just like other life forms.