Difference Between Cytochrome C and Other Cytochromes

The key difference between cytochrome C and other cytochromes is that cytochrome C is an essential component of the electron transport chain while other cytochromes are not.

Cytochromes are hemeproteins. In simple words, they are heme-containing proteins. There are four major types of cytochromes based on the kind of prosthetic heme group: cytochromes a, cytochromes b, cytochromes c and cytochrome d. Some are globular proteins, while others are membrane proteins. Basically, cytochromes are electron transfer proteins. Among these four types, cytochrome c is functionally important for the electron transport chain. It is also the most stable and abundant member of the cytochrome family.

CONTENTS

1. Overview and Key Difference
2. What is Cytochrome C  
3. What are Other Cytochromes
4. Similarities Between Cytochrome C and Other Cytochromes
5. Side by Side Comparison – Cytochrome C vs Other Cytochromes in Tabular Form
6. Summary

What is Cytochrome C?

Cytochrome c is a type of cytochrome which is an essential component in the electron transport chain of aerobic respiration. Cytochrome c transfers an electron from cytochrome reductase to cytochrome oxidase. In addition to acting as an electron carrier, cytochrome c participates in apoptosis. Moreover, it catalyzes several redox reactions, such as hydroxylation and aromatic oxidation, etc. It is a small heme protein found in the inner membrane of mitochondria. The molecular weight is about 12 kDa. Approximately, it is spherical in shape. This protein contains a single heme group.

Cytochrome c is a highly water-soluble protein. It has a very long carbon chain attached. CYCS gene in the human genome encodes for cytochrome c. Moreover, it is a highly conserved protein found in animals, plants and unicellular organisms.

What are Other Cytochromes?

Cytochrome a, b and d are the other three types of cytochromes. They contain heme a, b and d respectively as their prosthetic groups. Irons in cytochrome exist in ferrous (Fe²⁺) and a ferric (Fe³⁺) state. They are capable of taking part in electron transfer reactions as well as catalysis by redox reactions. Therefore, they mainly participate in the energy conversion processes of the organisms. Cytochromes are found in many anaerobic organisms and in all aerobic organisms.

What are the Similarities Between Cytochrome C and Other Cytochromes?

• Cytochromes are heme proteins.
• They are present in many anaerobic organisms and in all aerobic organisms.
• They participate in electron transfer reactions and catalysis by redox reactions.
• Moreover, they all contain an iron atom.

What is the Difference Between Cytochrome C and Other Cytochromes?

Cytochrome c is functionally involved in the electron transport chain of mitochondria. Other cytochromes do not participate in the electron transport chain. So, this is the key difference between cytochrome c and other cytochromes. Besides, cytochrome c has heme c prosthetic group while cytochrome a, b and c have heme a, b and d prosthetic groups, respectively.

The following table summarizes the difference between cytochrome c and other cytochromes.

Summary – Cytochrome C vs Other Cytochromes

Cytochromes are proteins containing one or more heme groups. Cytochrome a, b, c and d are the four main types of cytochromes. They differ from each other based on the kind of heme group. Cytochrome c has heme c while other cytochromes have heme a, b and d. Moreover, cytochrome c is an important component of the electron transport chain while other cytochromes do not participate in the electron transport chain. Thus, this is the key difference between cytochrome c and other cytochromes.

Reference:

1. “Cytochrome C”. Chemistry Libretexts, 2020, Available here.
2. “Cytochromes – An Overview”. Sciencedirect.Com, 2020, Available here.

Image Courtesy:

1. “Cytochrome C” By Vossman – Own work (CC BY-SA 3.0) via Commons Wikimedia