This is Chapter 2 – Cells for the Year 12 Biology course.

This chapter develops students’ understanding of the cell from a mostly structural model into a dynamic system in which matter, energy and information are constantly exchanged and regulated. Many ideas will be familiar from Stage 1 Biology, but they are now examined in greater detail and connected more carefully to cellular function.

We begin with cell theory and the fluid mosaic model of the cell membrane. Students examine how phospholipids, cholesterol and membrane proteins create a selectively permeable boundary. They then use factors such as molecular size, polarity, charge and concentration gradients to predict how substances move through diffusion, osmosis, facilitated diffusion and active transport.

The structures of prokaryotic and eukaryotic cells are compared, with a strong focus on how specialised organelles support particular functions. Energy transformations are then explored through photosynthesis, aerobic respiration and anaerobic fermentation. The ATP–ADP cycle provides the central link between energy-releasing and energy-requiring cellular processes.

Metabolic pathways are studied as organised sequences of enzyme-controlled reactions. Students examine how intermediate products are formed, why some energy is lost as heat and how competitive and non-competitive inhibitors can disrupt pathway activity.

The final sections focus on cell division and regulation. Binary fission, mitosis and meiosis are compared before students investigate how crossing over and independent assortment generate genetic variation. The cell cycle is then examined as a carefully controlled process, including the internal and external signals that regulate progression and the consequences of losing this control.

These ideas provide important foundations for genetics, cancer biology, physiology, biotechnology and evolutionary biology.

Subtopics:

• A: Cell Theory and Cell Membrane

• B: Prokaryotic vs Eukaryotic
• C: Energy Transformations
• D: Metabolic Pathways
• E: Cell Division
• F: Meiosis
• G: The Cell Cycle

By the end of this topic, students will be able to explain cellular structure and transport, describe energy transformations and metabolic regulation, and analyse how cell division supports growth, reproduction and genetic variation.