• Cells are the smallest unit of living organisms, such as muscle, red blood, and nerve cells
• Cells form tissues, which are groups of cells with similar structures and functions, like muscles
• Tissues make up organs, which are made of different tissues, like the stomach
• Organs work together in organ systems, such as the digestive system
• Enzymes in the digestive system break down food into smaller molecules to provide energy for the body

Understanding the organization of cells in living organisms, the functions of the digestive system, and the work of enzymes in the human body are essential aspects of AQA GCSE Biology B3. By learning about these topics and their interrelationships, students can build a strong foundation for understanding the complexities of living organisms and their functions.