Course Overview and Specification

This AQA Biology unit dives into the fascinating world of cell structure, covering everything you need to ace your exams. You'll explore three main areas: eukaryotic cells (like yours), prokaryotic cells (bacteria), and how scientists study cells using microscopes.

The course breaks down into manageable chunks with specific lesson targets and exam questions. Each section builds on the previous one, starting with complex eukaryotic cells before moving to simpler prokaryotic structures and viruses.

You'll also master practical skills like using microscopes and calculating magnification - essential techniques that often appear in exam questions. The final section covers advanced laboratory methods like ultracentrifugation, showing how scientists separate different cell components.

Quick Tip: Pay attention to the lesson structure - each section has specific mark allocations that hint at exam importance.

Key Cell Types and Structures

Eukaryotic cells are the complex cells found in plants, animals, and fungi. They're packed with membrane-bound organelles like the nucleus, mitochondria, and Golgi apparatus. In plants, you'll also find chloroplasts and cell walls made of cellulose.

These cells can become highly specialised for specific jobs - think muscle cells for movement or red blood cells for oxygen transport. This specialisation follows a hierarchy: cells form tissues, tissues form organs, and organs form complete systems.

Prokaryotic cells (bacteria) are much simpler and smaller. Instead of a nucleus, their DNA floats freely in the cytoplasm as a circular molecule. They have smaller ribosomes and cell walls made of murein rather than cellulose.

Viruses aren't even proper cells - they're just genetic material wrapped in a protein coat called a capsid. They can't survive on their own and need to hijack other cells to reproduce.

Remember: The key difference is membrane-bound organelles - eukaryotes have them, prokaryotes don't!

Microscopy and Key Terms

Understanding magnification versus resolution is crucial for your exams. Magnification is how much bigger something appears, whilst resolution is how much detail you can actually see.

Optical microscopes use light and can magnify up to about 1500x, but they're limited by light wavelengths. Electron microscopes use electron beams instead, giving much higher magnification and resolution - perfect for seeing organelles in detail.

There are two types of electron microscopes: transmission electron microscopes (TEM) show internal structures, whilst scanning electron microscopes (SEM) create detailed 3D surface images.

Cell fractionation and ultracentrifugation allow scientists to separate different cell components by spinning them at incredibly high speeds. Heavier organelles settle out first, followed by lighter ones.

Exam Focus: You must know the magnification formula: Magnification = Image size ÷ Actual size

Essential Vocabulary

This comprehensive key word list covers all the technical terms you'll encounter in cell structure topics. Master these definitions and you'll handle any exam question with confidence.

Key transport terms include carrier proteins for facilitated diffusion and ion channels that allow specific particles through membranes. Understanding isotonic solutions helps explain why cells maintain their shape.

Differentiation explains how cells become specialised, whilst mitosis and meiosis describe different types of cell division. Metabolism encompasses all chemical processes in living organisms.

Plant-specific terms like phloem, xylem, and stomata relate to transport and gas exchange. Chloroplasts contain thylakoids and grana where photosynthesis occurs.

Study Tip: Don't just memorise - understand how these terms connect to create living systems.

Eukaryotic Cell Organelles

Eukaryotic cells contain numerous organelles, each with specific functions that keep the cell alive and working efficiently. Learning these structures and their jobs is essential for understanding how complex life forms operate.

The nucleus controls the cell and contains DNA organised into chromosomes. Mitochondria are the powerhouses, producing energy through respiration with their folded inner membranes called cristae.

Ribosomes make proteins either freely in the cytoplasm or attached to the rough endoplasmic reticulum (RER). The smooth endoplasmic reticulum (SER) lacks ribosomes and handles lipid synthesis instead.

The Golgi apparatus modifies and packages proteins from the ER, whilst lysosomes digest waste materials. Plant cells additionally have chloroplasts for photosynthesis and cell walls made of cellulose for support.

Memory Trick: Think of the cell as a factory - each organelle has a specific job in the production line!