Cell Biology: The Building Blocks of Life

By the end of the lesson, students should be able to:

Define what a cell is and explain why it is the basic unit of life.

Compare the structure of animal and plant cells.

Describe the functions of key organelles.

Understand the levels of organisation (cell → tissue → organ → system → organism).

What is a Cell?

The smallest structural and functional unit of life.

All living organisms are made of cells (cell theory).

Types of Cells

Prokaryotic cells (bacteria: no nucleus, smaller, simpler).

Eukaryotic cells (plant and animal cells: have nucleus and organelles).

Plant vs Animal Cells

Shared organelles: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes.

Plant-specific: cell wall, chloroplasts, large vacuole.

Functions of Key Organelles

Nucleus – control centre, stores DNA.

Mitochondria – site of respiration, releases energy.

Ribosomes – protein synthesis.

Cytoplasm – site of chemical reactions.

Cell membrane – controls entry/exit of substances.

Chloroplasts – photosynthesis in plants.

Levels of Organisation

Cell → Tissue → Organ → Organ System → Organism.