In mitochondria, ATP synthesis occurs

Options

A. in the matrix
B. in the intracristal space
C. at the outer membrane
D. at the outer membrane

Answer

### Step-by-Step Solution:

1. **Understanding Mitochondria Structure**: Mitochondria are double-membraned organelles found in eukaryotic cells. They consist of an outer membrane and a highly folded inner membrane.

2. **Identifying Key Components**: The inner membrane of the mitochondria is folded into structures known as cristae. The space inside the inner membrane is called the mitochondrial matrix, while the space between the inner and outer membranes is referred to as the intermembrane space.

3. **ATP Synthesis Location**: ATP (adenosine triphosphate) synthesis occurs in the mitochondria through a process called oxidative phosphorylation. This process primarily takes place along the inner membrane where the electron transport chain is located.

4. **Mechanism of ATP Production**: As electrons are passed along the electron transport chain (composed of cytochromes and coenzymes), energy is released. This energy is used to pump protons (H⁺ ions) from the matrix into the intermembrane space, creating a proton gradient.

5. **Final Steps of ATP Synthesis**: The protons then flow back into the matrix through ATP synthase, an enzyme located in the inner membrane. The flow of protons drives the conversion of ADP (adenosine diphosphate) and inorganic phosphate into ATP.

6. **Conclusion**: Therefore, the correct answer to the question is that ATP synthesis occurs in the inner membrane of the mitochondria, specifically at the cristae.

### Final Answer:
ATP synthesis occurs in the inner membrane of the mitochondria, specifically at the cristae.

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