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 of 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.
Health

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.

What are Cytochromes?

By Helga George
Updated: May 17, 2024
Views: 28,551
Share

Cytochromes are enzymes that contain iron in the form of a heme in their active site. They are involved with the transport of electrons during cellular respiration. A separate class is cytochrome P450s, which carry out detoxification reactions and synthesize compounds, such as steroids. Both types of enzymes are found in membranes.

There are several different types of cytochromes, and these are distinguished in a variety of ways, including by spectroscopy and sensitivity to inhibitors. They are cytochromes a, b, and c — and each has subtypes. They vary in the environment that the protein provides for its heme group, and this affects the ability of the cytochrome to transfer electrons.

The transfer of electrons is part of the respiratory cycle. Respiration takes place in all cells of the body, and provides energy in the form of adenosine triphosphate (ATP). This compound is a universal source of energy for cells. Energy-rich glucose is broken down in the mitochondria, which are the furnaces for the cells. The enzymes involved in the respiratory chain are located in the wall of the mitochondria.

The electrons from the degradation of glucose are transferred, step-by-step, down a gradient of enzymes composed predominantly of cytochromes. At each step, energy is released. This is sometimes called the cytochrome system.

The iron in the active site of the cytochromes varies between being in a reduced or oxidized form. The flow of the electrons occurs when they shift from a reducing agent to an oxidizing agent. The final step is the transfer of two electrons from cytochrome c oxidase to oxygen, which forms water. This step is coupled to ATP formation, and is known as oxidative phosphorylation.

Proteins that contain heme groups are known as hemoproteins, and the hemes of some of the cytochromes differ from each other. Along with the differences in the protein structures, this helps ensure that the cytochromes have varying reducing potentials. Thus, they are located at different points in the respiratory chain, which are optimal for their electron transfer. These enzymes are also found in the membranes of the mitochondria, the endoplasmic reticulum, and in the chloroplasts of plants.

Cytochrome P450s are an entirely different group of enzymes. Instead of oxidizing their substrates, they incorporate an atom of molecular atom. Thus, they are monooxygenases, not oxidases like the other cytochromes. They also have a heme group at their active site.

P450s are a very diverse group of enzymes. There are a number of different types in the liver, where they detoxify foreign substances, such as drugs. These also detoxify many of the compounds found in the plants people eat. It is thought that many of these P450s evolved as a human defense against the toxic compounds found in plants. Other types of these enzymes are involved in the biosynthesis of steroids and hormones.

Share
WiseGeek 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.

Editors' Picks

Discussion Comments
By anon1004230 — On Dec 17, 2020

This article is great but it stopped just as it started getting wild.

Share
https://www.wisegeek.net/what-are-cytochromes.htm
Copy this link
WiseGeek, in your inbox

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

WiseGeek, in your inbox

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