OCR GCSE Biology Practice Exam 2025 – Comprehensive All-in-One Guide to Exam Success

The primary function of Prozac, which is a selective serotonin reuptake inhibitor (SSRI), is to block the reabsorption (degradation) of serotonin in the brain. By inhibiting the reuptake of serotonin, Prozac increases the amount of serotonin available in the synaptic cleft, which can help improve mood and alleviate symptoms of depression and anxiety. This mechanism is crucial because serotonin is a key neurotransmitter involved in regulating mood, and its low levels are often associated with depressive disorders.

The other options do not accurately reflect the primary role of Prozac. For instance, inducing sleep is not its main function; while some individuals might experience changes in sleep patterns, this is a secondary effect. Similarly, facilitating pain relief is not the core purpose of Prozac; its primary focus is on mood regulation. Lastly, decreasing serotonin levels contradicts the drug's intended effect, as it is designed to increase serotonin activity rather than diminish it.