Step 1: Understanding ATP synthesis.
ATP (adenosine triphosphate) is the energy currency of the cell. It is primarily synthesized during cellular respiration, which occurs in the mitochondria through oxidative phosphorylation.
Step 2: Evaluating the options.
- **Chloroplast**: Involved in photosynthesis in plants, not the main site for oxidative ATP synthesis.
- **Nucleus**: Stores genetic material and regulates cellular activities, but not ATP synthesis.
- **Ribosome**: Responsible for protein synthesis, not energy production.
- **Mitochondrion**: The site of the electron transport chain and oxidative phosphorylation, generating ATP. Known as the powerhouse of the cell.
Step 3: Conclusion.
The correct answer is Mitochondrion.
Final Answer: \[ \boxed{\text{Mitochondrion is the powerhouse of the cell.}} \]
Rearrange the following parts to form a meaningful and grammatically correct sentence:
P. a healthy diet and regular exercise
Q. are important habits
R. that help maintain good physical and mental health
S. especially in today's busy world