Question

In which part of the cell would you expect to find cytochrome c? A. Mitochondrial matrix B. Outer mitochondrial membrane C. Inner mitochondrial membrane D. Cytosol

Short answer

C. Inner mitochondrial membrane

Step-by-step solution

Understand Cytochrome c

Cytochrome c is a small heme protein associated with the process of electron transport in cells.

Role of Cytochrome c

It plays a critical role in the electron transport chain, which is a part of cellular respiration.

Location of the Electron Transport Chain

The electron transport chain takes place across the inner mitochondrial membrane.

Identify the Correct Part of the Cell

Since cytochrome c is involved in the electron transport chain, it should be located in the inner mitochondrial membrane where this process occurs.

Key concepts

Mitochondria

Mitochondria are often called the 'powerhouses' of the cell. They are tiny organelles found in large numbers in almost all eukaryotic cells.
Mitochondria generate the energy needed for various cellular processes through a series of chemical reactions. These reactions take place in two main regions within the mitochondria: the mitochondrial matrix and the inner mitochondrial membrane.

The mitochondrial matrix is the innermost part, containing enzymes essential for the Krebs cycle, also known as the citric acid cycle. This cycle produces molecules that carry electrons to the next phase: the electron transport chain.
The inner mitochondrial membrane has a very important role. It hosts the electron transport chain, where a series of proteins and enzymes help produce adenosine triphosphate (ATP), the main energy currency of the cell.

Electron Transport Chain

The electron transport chain (ETC) is the final stage of cellular respiration. It takes place in the inner mitochondrial membrane and is critical for ATP production.
The ETC includes a variety of protein complexes and molecules, including cytochromes like cytochrome c. These proteins transfer electrons from molecules like NADH and FADH2 down the chain.

As electrons move through the chain, energy is released. This energy is used to pump protons (H+ ions) across the inner mitochondrial membrane, creating a gradient. The gradient drives the synthesis of ATP as protons flow back into the mitochondrial matrix through a molecule called ATP synthase.

Cellular Respiration

Cellular respiration is the process by which cells generate energy from nutrients. This complex process occurs in three main stages: Glycolysis, the Krebs cycle, and the Electron Transport Chain.
Glycolysis happens in the cytosol and breaks down glucose into pyruvate, producing a small amount of ATP and NADH.
The Krebs cycle occurs in the mitochondrial matrix and generates additional NADH and FADH2 molecules, which carry electrons to the Electron Transport Chain.

The Electron Transport Chain is the final and most significant stage for ATP production, taking place in the inner mitochondrial membrane. Oxygen, the final electron acceptor in the chain, combines with electrons and protons to form water, completing the process of ATP generation.