Lecture Notes: The Cell and Plasma Membrane

Basic Unit of Life

• Cell is the basic unit of life.
  • Defined as a limited space entity that performs metabolic functions.
  • Enclosed by a membrane known as the plasma membrane.

Plasma Membrane

• Also referred to as cell membrane.
• Defines the boundary of a cell; no cell exists without it.

Role of the Plasma Membrane

• Separates intercellular components from extracellular space.
• Defines boundaries for organelles in eukaryotic cells termed membrane-bound organelles.

Structure of the Plasma Membrane

• Explained using the Fluid Mosaic Model (proposed by Singer and Nicholson).
  • Composed of a lipid bilayer with embedded proteins.
  • Phospholipids: have hydrophilic heads (facing outward) and hydrophobic tails (facing inward).

Types of Proteins in the Membrane

1. Intrinsic Proteins (Integral Proteins)

   • Embedded in the lipid layer.
   • Functions: carriers, enzymes, transport channels, etc.

2. Extrinsic Proteins (Peripheral Proteins)

   • Loosely bound to the membrane.
   • Functions: receptors, recognition centers, etc.

Functions of the Cell Membrane

• Provides proper shape to the cell.
• Keeps adjacent cells in contact.
• Plays a crucial role in transport.
  • Selectively permeable and semi-permeable.
  • Only allows selective materials to pass through (e.g., water, minerals, ions, glucose, amino acids, oxygen, carbon dioxide).

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These details summarize the structure and function of the plasma membrane, emphasizing its importance to cellular integrity and function.