Lysosomes are membrane-bound organelles discovered by Christian de Duve in 1955, crucial for cellular digestion and maintaining homeostasis. They contain hydrolytic enzymes that break down excess cell parts, digest food, and engage in immune responses. Two types, primary and secondary lysosomes, are involved in various cell processes, and diseases associated with lysosomal dysfunction include Fabry disease and Tay-Sachs disease.

1. NAME ALISHBA RAFAQAT
ROLL NO F24-2604
SUBJECT CYTOLOGY
DEPARTMENT ZOOLOGY
SEMESTER 3rd
SUBMITTED TO DR. KAMRAN
DATED 9-12-2024

2. Lysosomes:
Discovery:
Christian de Duve discovered lysosomes in 1955 while working in his laboratory in
Louvain. De Duve was awarded the Nobel Prize in Physiology or Medicine in 1974
for his discovery, along with Albert Claude and George Palade.
Definition:
A lysosome is a membrane-bound cell organelle that contains digestive
enzymes. Lysosomes are involved with various cell processes. They break
down excess or worn-out cell parts. They may be used to destroy invading
viruses and bacteria.
Structure of Lysosomes:
Lysosomes are membrane-bound organelles and the area within the membrane is called
the lumen, which contains the hydrolytic enzymes and other cellular debris.
Lysosome show enzyme complexes within the single-walled membrane.
The pH level of the lumen lies between 4.5 and 5.0, which makes it quite acidic. It is
almost comparable to the function of acids found in the stomach.

3. Besides breaking down biological polymers, lysosomes are also involved in various other
cell processes such as counting discharged materials, energy metabolism, cell signalling,
and restoration of the plasma membrane.
The sizes of lysosomes vary, with the largest ones measuring in more at than 1.2 μm. But
they typically range from 0.1 μm to 0.6 μm.
Formation of Lysosomes:
Lysosomes are formed by budding off of the Golgi body, and thus the hydrolytic enzymes
contained within them are produced within the endoplasmic reticulum. The catalysts are
labeled with mannose-6-phosphate and transported to the Golgi body in vesicles before
being incorporated into the lysosomes.
Function of Lysosomes:
The primary function of lysosomes in the cell is to break down materials. Lysosomes
serve many purposes in the cell, such as:
 Breaking down larger polymers
 Digesting food
 Digesting extracellular material
 Aiding in the immune response
 Breaking down worn out cellular components
 Participating in apoptosis

4. Lysosomes break down larger polymers, such as lipids, carbohydrates, and proteins
into their component parts. As a result, some protists use lysosomes to help digest
food taken in from the environment.
Types of Lysosomes:
There are Two types of lysosomes.
1. Primary Lysosomes
2. Secondary Lysosomes
Primary Lysosomes:
Primary lysosomes are homogenous, membrane-bound organelles containing over 50 acid
hydrolase enzymes. These are newly formed vesicles from the Golgi apparatus. They are
small in size, and their hydrolytic enzymes come in the form of granules.
Secondary Lysosomes:
Secondary lysosomes are vesicles created from the fusion of primary lysosomes to
endosomes. Digestion then occurs and the digested food is exported into the cytoplasm.
The secondary lysosomes are left with the undigested food.
Disease of Lysosomes:
 Fabry Disease
 Mucopolysaccharidoses
 GM2 gangliosidoses
 Gaucher Disease
 Pompe Disease

5.  Tay –Sachs Disease
 Shortness of breath
 Niemann disease
 Batten Disease
Conclusion:
In conclusion, lysosomes are membrane-bound organelles that play a vital role in
maintaining cellular homeostasis. They are responsible for cellular digestion, recycling,
and defense against pathogens. The unique structure and function of lysosomes enable
them to perform these critical functions. Understanding the biology of lysosomes is
essential for appreciating their importance in maintaining cellular health and preventing
diseases.