Lysosomes | Lysosomes structure and function | class 11
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NOTES
Lysosomes*
1. Definition and Structure
Lysosomes are single membranous, spherical vesicles.
They contain digestive or hydrolytic enzymes.
The name "Lysosome" is derived from Greek words: "lyso" meaning splitting and "soma" meaning body.
2. Formation of Lysosomes
Enzyme Production: The lysosomal enzymes are synthesized by the rough endoplasmic reticulum (RER).
Transport: These enzymes are transported to the Golgi complex via the smooth endoplasmic reticulum (SER).
Modification and Release: After modification in the Golgi complex, enzymes are released from its trans face in the form of vesicles.
Primary Lysosomes: The newly formed lysosomes, before starting their function, are referred to as primary lysosomes.
3. Function of Lysosomes
Digestive Enzymes: Lysosomes contain about 40 different digestive enzymes capable of breaking down every major macromolecule of the cell.
Acidic Contents: The interior of lysosomes is acidic, which is necessary for enzyme activity.
4. Lysosomal Processes
Fusion with Vesicles: Lysosomes perform their functions by fusing with membrane-bound vesicles that arise from pathways such as:
Endocytosis
Phagocytosis
Autophagocytosis
Endocytosis: The process by which foreign particles are pulled into the cell by invagination of the cell membrane, creating a vacuole or pouch around the external contents and bringing them into the cell.
Autophagy: The process by which unwanted structures within the cell are engulfed and digested within lysosomes, also known as self-eating.
Autophagosomes: Lysosomes involved in autophagy are called autophagosomes.
Purpose: Autophagy occurs to obtain energy during starvation or to regulate the number of specific organelles, such as mitochondria, depending on cellular needs.
5. Lysosomes in Plants and Fungi
In plants and fungi, certain vacuoles carry out enzymatic hydrolysis, a function shared by lysosomes in animal cells.
6. Key Functions
Digestion: Lysosomes are responsible for the digestion and removal of waste within the cell.
Energy Regulation: During starvation or changes in activity, lysosomes help regulate the number of certain organelles, like mitochondria, through autophagy.
IMPORTANT SHORT QUESTIONS
What is the primary function of lysosomes?
From which part of the cell are lysosomal enzymes synthesized?
What are primary lysosomes?
Why is the interior of lysosomes acidic?
What role do lysosomes play in autophagy?
What are autophagosomes?
How are lysosomal enzymes transported to the Golgi complex?
What is the significance of lysosomes in energy regulation during starvation?