We are independent & ad-supported. We may earn a commission for purchases made through our links.

Advertiser Disclosure

Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.

How We Make Money

We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently from our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What Is Substrate-Level Phosphorylation?

By A. Reed
Updated Mar 03, 2024
Our promise to you
The Health Board is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At The Health Board, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

Substrate-level phosphorylation encompasses certain chemical reactions that occur in human cells during glycolysis, the conversion of glucose leading to the production of two high energy molecules, referred to as adenosine triphosphate (ATP). This is accomplished through the chemical transfer of a phosphate group from each of two phosphoenolpyruvate (PEP) molecules, forming ADP, which is then transformed into ATP. In addition to ATP, glycolysis also yields two molecules of nicotinamide adenine dinucleotide (NADH) in reduced form and pyruvate, which is put into the next phase of cellular respiration.

ATP is the chief energy molecule used by cells, driving all processes occurring within it, of which substrate-level phosphorylation has a small, although important, role and is actually one of two ways ATP is produced from ADP in humans. Oxidative phosphorylation is the other mechanism necessary for making energy, most of which happens inside of the mitochondria of the cell. Often referred to as the powerhouse of the cell, the mitochondria is the organelle in which all stages of cellular respiration occur, except glycolysis. All steps in glycolysis, including substrate-level phosphorylation, happen in the cell's cytosol, fluid containing all cellular components such as the nucleus and ribosomes.

Cellular respiration in humans occurs aerobically and consists of four stages of reactions through which food is converted into ATP. Glycolysis is the beginning of the process of which substrate-level phosphorylation is the last step. Next, pyruvate from glycolysis is used to form acetyl coenzyme A, from which the waste product carbon dioxide is released. With the Krebs cycle, part of the coenzyme is used to make yet another chemical called citrate, more carbon dioxide is released as ATP, NADH, and another energy-yielding molecule referred to as flavin adenine dinucleotide (FADH2) are also end products. The last of these stages is the electron transport chain and chemiosmosis, by which energy taken from glucose, NADH, and FADH2 is used in the movement of hydrogen ions across the membrane of the mitochondria, as well as for the production of more ATP.

Pyruvate kinase is the enzyme responsible for catalyzing substrate-level phosphorylation. Other chemical reactions of glycolysis and subsequent cellular respiration phases involve the action of a certain enzyme, a protein necessary for controlling the speed of reactions, which is very important for meeting energy requirements of the human body, as it takes only a minute to consume all available ATP. Once the reaction is complete, the enzyme is recycled and used again.

The Health Board is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.

Discussion Comments

By turquoise — On Dec 08, 2011

@burcidi-- Those are good points.

If I remember correctly from bio classes, there are three or so ways that ATP can be made/broken down. Glycolysis and oxidative phosphorylation is two, and then there is also the citric acid cyle (also caled the Kreb's cycle).

Substrate-level phopshorylation happens in both glycolysis and the Kreb's cycle. The only difference is that the Kreb cycle is also in the mitochondria and glycolysis is not (it's in the cytoplasm).

You might also want to specify for those who don't know, that the 2 ATP from glycolysis is per 1 glucose molecule.

It had been a long time since I studied this, it's been a good review!

By burcidi — On Dec 08, 2011

@ddljohn-- Yes. But keep in mind that substrate-level phosphorylation is not the only way that cells make energy. This is just how glycolysis happens outside of the mitochondria.

Glycolysis (substrate-level phosphorylation) only produces 2 ATP at a time. Aerobic respiration (oxidative phosphorylation) on the other hand produces over 30 at a time. So there is no way that glycolysis could fulfill all of the energy needs of the cell by itself.

The other point is that substrate-level phosphorylation doesn't just turn ADP into ATP; it also transforms ATP into ADP. When you also consider that, substrate-level phosphorylation is going on all the time.

By ddljohn — On Dec 07, 2011

The last paragraph of the article is really interesting. If our cells use up all of the available ATP in only one minute, cellular respiration, substrate-level phosphorylation and ATP production must be going on constantly in the body, right?

Does this process every take a break, when we're sleeping for example? Or are we doing this all the time to maintain our life?

If the latter is true, then it's pretty amazing that our cells can do this without fail from our birth to death, don't you think?

The Health Board, in your inbox

Our latest articles, guides, and more, delivered daily.

The Health Board, in your inbox

Our latest articles, guides, and more, delivered daily.