Introduction

Cells are the basic units of life. Every living organism is made up of cells, which perform essential functions to sustain life. Understanding cell structure and function is one of the most important foundations in biology basics.

Cell Theory

1. All living things are composed of cells.
2. Cells are the smallest units of life.
3. All cells come from pre‑existing cells.

This theory forms the cornerstone of modern biology.

Types of Cells

1. Prokaryotic Cells: Simple cells without a nucleus (e.g., bacteria).
2. Eukaryotic Cells: Complex cells with a nucleus and organelles (e.g., plants, animals, fungi).

Structure of Eukaryotic Cells

Cells contain specialized structures called organelles, each with unique functions:

1. Nucleus: Controls cell activities and stores DNA.
2. Mitochondria: Produces energy (ATP) through respiration.
3. Ribosomes: Synthesizes proteins.
4. Endoplasmic Reticulum (ER): Processes and transports proteins and lipids.
5. Golgi Apparatus: Packages and distributes molecules.
6. Lysosomes: Break down waste and cellular debris.
7. Cell Membrane: Regulates entry and exit of substances.
8. Cytoplasm: Jelly‑like fluid where organelles are suspended.

Plant vs. Animal Cells

1. Plant Cells:
2. Have a rigid cell wall.
3. Contain chloroplasts for photosynthesis.
4. Large central vacuole for storage.
5. Animal Cells:
6. Lack a cell wall.
7. Do not have chloroplasts.
8. Smaller vacuoles.

Importance of Cells

1. Cells carry out essential processes like energy production, protein synthesis, and waste removal.
2. Specialized cells (e.g., nerve cells, muscle cells) perform unique functions in multicellular organisms.
3. Studying cells helps scientists understand diseases, develop medicines, and advance biotechnology.

Summary

Cells are the building blocks of life. By studying their structure and function, students gain a deeper understanding of how living organisms grow, reproduce, and survive. Mastering cell biology is the first step toward exploring advanced topics in biology.