PROTOPLASM
Biology Notes for Students | Cell Structure & Function
1. What is Protoplasm?
Definition: Protoplasm is the semi-liquid, jelly-like, sticky, granular, and colorless living substance of the cell. It is
the physical basis of life and is present in all living cells.
Composition: Made up of various organic and inorganic compounds. It contains approximately 67% to 90% water.
Other components include proteins, lipids, carbohydrates, nucleic acids, and mineral salts.
2. Major Parts of Protoplasm
Part Description
① Cell Membrane Soft outer boundary surrounding the entire protoplasm. Also called biomembrane.
(Plasma Membrane)
② Cytoplasm Jelly-like fluid portion of the protoplasm located outside the nucleus.
③ Nucleus Control centre of the cell containing genetic material (DNA).
A. Cell Membrane (Plasma Membrane / Biomembrane)
Structure: A soft, thin membrane that surrounds the entire protoplasm. It is composed of a double layer of
phospholipids (phospholipid bilayer) with embedded proteins. It is also known as a biomembrane because it is living
and selectively permeable.
Function: Controls the transport of water, minerals, gases, and other substances into and out of the cell. It acts as a
selective barrier, allowing some materials to pass while restricting others (selective permeability).
Key Point: The cell membrane maintains the internal environment of the cell and protects it from the external surroundings.
B. Cytoplasm
Definition: The jelly-like fluid portion of the protoplasm located outside the nucleus. It is the site of many metabolic
activities and contains various living structures called cytoplasmic organelles.
Cytoplasmic Organelles: Living structures suspended within the cytoplasm that carry out specific metabolic activities
essential for the life of the cell.
Key Organelles found in the Cytoplasm:
Student Notes • Protoplasm • Page 1 of 3
Biology Notes for Students | Cell Structure & Function
1. What is Protoplasm?
Definition: Protoplasm is the semi-liquid, jelly-like, sticky, granular, and colorless living substance of the cell. It is
the physical basis of life and is present in all living cells.
Composition: Made up of various organic and inorganic compounds. It contains approximately 67% to 90% water.
Other components include proteins, lipids, carbohydrates, nucleic acids, and mineral salts.
2. Major Parts of Protoplasm
Part Description
① Cell Membrane Soft outer boundary surrounding the entire protoplasm. Also called biomembrane.
(Plasma Membrane)
② Cytoplasm Jelly-like fluid portion of the protoplasm located outside the nucleus.
③ Nucleus Control centre of the cell containing genetic material (DNA).
A. Cell Membrane (Plasma Membrane / Biomembrane)
Structure: A soft, thin membrane that surrounds the entire protoplasm. It is composed of a double layer of
phospholipids (phospholipid bilayer) with embedded proteins. It is also known as a biomembrane because it is living
and selectively permeable.
Function: Controls the transport of water, minerals, gases, and other substances into and out of the cell. It acts as a
selective barrier, allowing some materials to pass while restricting others (selective permeability).
Key Point: The cell membrane maintains the internal environment of the cell and protects it from the external surroundings.
B. Cytoplasm
Definition: The jelly-like fluid portion of the protoplasm located outside the nucleus. It is the site of many metabolic
activities and contains various living structures called cytoplasmic organelles.
Cytoplasmic Organelles: Living structures suspended within the cytoplasm that carry out specific metabolic activities
essential for the life of the cell.
Key Organelles found in the Cytoplasm:
Student Notes • Protoplasm • Page 1 of 3
