key term - Cytochrome c

Definition

Cytochrome c is a small heme protein found in the mitochondria of eukaryotic cells, playing a crucial role in the electron transport chain and cellular respiration. It functions as an electron carrier, shuttling electrons between complex III and complex IV, and is essential for ATP production during oxidative phosphorylation. Additionally, cytochrome c has important implications in programmed cell death, linking energy metabolism to apoptosis.

5 Must Know Facts For Your Next Test

1. Cytochrome c contains a heme group that allows it to participate in redox reactions, facilitating electron transfer during cellular respiration.
2. It is located in the intermembrane space of mitochondria, where it transfers electrons to cytochrome c oxidase (complex IV) after receiving them from ubiquinol (from complex III).
3. During apoptosis, cytochrome c is released from the mitochondria into the cytosol, triggering a cascade of events that lead to cell death through the activation of caspases.
4. The structure of cytochrome c is highly conserved across species, indicating its fundamental role in cellular metabolism and energy production.
5. Mutations or deficiencies in cytochrome c can lead to metabolic disorders and increased susceptibility to apoptosis-related diseases, such as cancer.

Review Questions

• How does cytochrome c function within the electron transport chain?
  • Cytochrome c plays a critical role in the electron transport chain by transferring electrons between complex III and complex IV. After receiving electrons from ubiquinol at complex III, cytochrome c becomes reduced and then donates these electrons to cytochrome c oxidase (complex IV). This transfer is essential for maintaining the flow of electrons through the chain, ultimately contributing to the proton gradient necessary for ATP synthesis.
• What is the relationship between cytochrome c and apoptosis?
  • Cytochrome c is intimately linked to apoptosis as its release from mitochondria into the cytosol is one of the key events signaling programmed cell death. Once in the cytosol, it activates apoptosomes, leading to the recruitment and activation of caspases. This cascade initiates the systematic dismantling of cellular components, highlighting how cytochrome c acts as a bridge between cellular respiration and cell death mechanisms.
• Evaluate the implications of cytochrome c mutations on cell survival and disease progression.
  • Mutations or deficiencies in cytochrome c can significantly impact cellular functions and lead to various diseases. For example, impaired electron transport can reduce ATP production, causing metabolic disorders. Furthermore, abnormal regulation of cytochrome c can influence apoptosis pathways; either excessive apoptosis may contribute to neurodegenerative diseases or insufficient apoptosis may allow cancer cells to evade death. Thus, understanding these mutations provides insight into therapeutic strategies for targeting metabolic and apoptotic pathways.

Related terms

Electron Transport Chain: A series of protein complexes and other molecules that transfer electrons through a membrane within the mitochondria, ultimately driving ATP synthesis.

Apoptosis: A programmed process of cell death that occurs in multicellular organisms, characterized by specific cellular changes and often involving cytochrome c release from mitochondria.

Heme Group: An iron-containing compound that binds to oxygen and plays a critical role in the function of hemoglobin and various cytochromes, including cytochrome c.