This AQA AS Biology exam focuses on various biological concepts, including enzymatic activity, plant physiology, and adaptations to environmental conditions. It covers the action of enzymes such as endopeptidases and exopeptidases in protein hydrolysis, mechanisms of amino acid absorption, and plant adaptations like stomata distribution in xerophytes. Key topics also include gas exchange in tubifex worms, the effects of pollution on oxygen levels, and the diversity of dung beetles across different farming practices. Additionally, students explore the effects of ageing and smoking on lung function, as well as genetic mutations and plant responses to environmental stimuli.