Lysosome: Structure, Functions & Importance

Introduction

Lysosomes are membrane-bound organelles found in eukaryotic cells. They contain powerful digestive enzymes that help in breaking down waste materials, old organelles, and foreign particles. Due to this function, lysosomes are often called the “suicide bags of the cell.”

Discovery

Lysosomes were discovered by Christian de Duve in 1955.

Structure of Lysosome

• Surrounded by a single membrane
• Filled with digestive enzymes
• Spherical in shape
• Acidic interior (pH ~4.5–5)
• Enzymes include proteases, lipases, nucleases, and carbohydrases

Functions of Lysosome

1. Intracellular Digestion – Breaks down food particles

2. Autophagy – Digestion of worn-out cell organelles

3. Autolysis – Destruction of damaged or dead cells

4. Defense – Destroys bacteria and viruses

5. Recycling – Reuses useful materials

Why are Lysosomes called Suicide Bags?

Lysosomes contain powerful digestive enzymes. If these enzymes are released into the cell, they can digest the entire cell, leading to its death. This process is known as autolysis.

Diagram (To be added)

Labeled diagram of Lysosome

Key Points for Exams

• Found only in eukaryotic cells
• Most abundant in animal cells
• Acidic nature helps enzyme activity
• Important for cell cleanup

MCQs

1. Lysosomes are found in:
A) Prokaryotic cells
B) Plant cells only
C) Animal cells
D) Bacterial cells

Answer: C

2. Lysosomes are also called:
A) Powerhouse
B) Suicide bags
C) Brain of cell
D) Protein factory

Answer: B

3. The pH inside lysosome is:
A) Neutral
B) Basic
C) Acidic
D) Alkaline

Answer: C

4. Who discovered lysosomes?
A) Robert Hooke
B) Leeuwenhoek
C) Christian de Duve
D) Watson

Answer: C

5. Autophagy means:
A) Cell division
B) Cell respiration
C) Digestion of old organelles
D) Protein synthesis

Answer: C