A-Level Biology: Cells Lesson-by-Lesson Breakdown

Lesson 1: Introduction to cells and cell theory

Focus: Cell theory; why all living things are made of cells; cells as the basic unit of life.

Students should learn:

• that all life exists as cells
• that cells share common basic features
• that all cells arise from other cells
• that the cell theory is a unifying concept in biology

Good outcome: Students can explain why cells are considered the fundamental unit of living organisms.

Lesson 2: Eukaryotic cell structure

Focus: Organelles in eukaryotic cells; structure and function.

Students should learn:

• the structure and function of the cell-surface membrane
• nucleus and nucleolus
• mitochondria
• chloroplasts
• Golgi apparatus and vesicles
• lysosomes
• ribosomes
• rough and smooth endoplasmic reticulum
• cell wall and vacuole in plant cells

Good outcome: Students can identify organelles and relate their structure to their function.

Lesson 3: Prokaryotic cells and viruses

Focus: Comparing prokaryotes and eukaryotes; viruses as acellular particles.

Students should learn:

• that prokaryotic cells are smaller than eukaryotic cells
• that prokaryotes lack membrane-bound organelles
• features such as circular DNA, plasmids, capsules, flagella, and murein cell walls
• that viruses are acellular and include genetic material, capsid, and attachment proteins

Good outcome: Students can compare eukaryotes, prokaryotes, and viruses clearly.

Lesson 4: Microscopy and studying cells

Focus: Optical and electron microscopes; magnification and resolution; measuring cells.

Students should learn:

• the principles and limitations of optical microscopes
• the role of transmission electron microscopes
• the role of scanning electron microscopes
• the difference between magnification and resolution
• how to measure the size of objects viewed under a microscope
• the basics of cell fractionation and ultracentrifugation

Good outcome: Students can interpret microscope images and calculate actual size from magnification.

Lesson 5: Cell division I — the cell cycle and mitosis

Focus: Interphase; mitosis stages; cytokinesis.

Students should learn:

• that DNA replication occurs during interphase
• the stages of mitosis: prophase, metaphase, anaphase, telophase
• the role of spindle fibres and centromeres
• that cytokinesis usually follows mitosis
• that mitosis produces two genetically identical daughter cells

Good outcome: Students can describe the cell cycle and identify each stage of mitosis.

Lesson 6: Cell division II — binary fission, cancer, and practical mitosis

Focus: Division in prokaryotes; uncontrolled cell division; root tip practical.

Students should learn:

• that prokaryotes divide by binary fission
• how circular DNA and plasmids replicate in prokaryotes
• that uncontrolled cell division can form tumours and cancers
• how to identify stages of mitosis in stained root tip cells
• how to calculate a mitotic index

Suggested practical:

• stained squash of plant root tip cells
• microscope observation of mitosis
• mitotic index calculation

Good outcome: Students can connect cell division theory to microscope-based practical work.

Lesson 7: Membrane structure

Focus: Cell membrane structure; fluid mosaic model.

Students should learn:

• that cell membranes have a common basic structure
• the fluid mosaic model
• the roles of phospholipids, proteins, glycoproteins, glycolipids, and cholesterol
• that membrane proteins are involved in transport and cell signalling

Good outcome: Students can explain how membrane structure supports membrane function.

Lesson 8: Transport across cell membranes

Focus: Diffusion; facilitated diffusion; osmosis; active transport; co-transport.

Students should learn:

• simple diffusion
• facilitated diffusion using channel and carrier proteins
• osmosis in terms of water potential
• active transport involving ATP
• co-transport, such as sodium and glucose absorption
• how surface area, transport proteins, and gradients affect transport rate

Suggested practical:

• membrane permeability investigation
• determining water potential of plant tissue

Good outcome: Students can compare transport mechanisms and explain which one operates in a given example.

Lesson 9: Cell specialisation and organisation

Focus: Specialised cells; tissues, organs, systems; stem cells and differentiation.

Students should learn:

• that cells in multicellular organisms become specialised
• that specialised cells are organised into tissues, organs, and systems
• that Edexcel also includes stem cells, totipotency, pluripotency, and differential gene expression
• that OCR frames this area as cell division, cell diversity and cellular organisation within Module 2

Good outcome: Students can explain how cell structure changes with function and how cells are organised in larger organisms.

Lesson 10: Review, application, and exam practice

Focus: Bringing the topic together; practical and data skills.

Students should practise:

• comparing eukaryotic, prokaryotic, and viral structures
• identifying organelles in diagrams and microscope images
• calculating magnification and actual size
• explaining stages of mitosis
• comparing membrane transport processes
• applying knowledge of specialised cells and organisation

Good outcome: Students can apply cell biology knowledge in unfamiliar exam questions, not just recall definitions.