Questions: A scientist grew Chlorella, a single-celled photosynthetic algae, for 3 weeks in a laboratory culture. The culture medium contained dissolved carbon dioxide and nitrogen compounds, but it did not contain phosphates. At the beginning and end of the 3 -week period, the scientist measured the rate of synthesis for certain biological molecules. Which of the following graphs shows the most likely results of the experiment? Choose 1 answer: (A) (B)

Solution Steps

The scientist grew Chlorella, a single-celled photosynthetic algae, for 3 weeks in a culture medium containing dissolved carbon dioxide and nitrogen compounds but no phosphates. The rate of synthesis for certain biological molecules was measured at the beginning and end of the period.

• Independent Variable: Presence of phosphates in the culture medium.
• Dependent Variable: Rate of synthesis for proteins, nucleic acids, lipids, and carbohydrates.

Phosphates are crucial for the synthesis of nucleic acids and ATP, which are essential for energy transfer and metabolism. Without phosphates, the synthesis of nucleic acids and possibly proteins would be limited.

• Graph A: Shows a decrease in the synthesis rate of nucleic acids and proteins, with a slight increase in lipids and carbohydrates.
• Graph B: Shows a significant decrease in the synthesis rate of nucleic acids and proteins, with a slight increase in lipids and carbohydrates.

Final Answer