B2.2.9 Structure and function of vesicles in cells (HL) Notes

Vesicles Facilitate Transport, Storage, and Digestion in Cells

1. Dynamic Nature: They are constantly forming, transporting, and fusing with other membranes, allowing the cell to rapidly adapt to changing needs.
2. Membrane Composition: Their bilayer structure is similar to the plasma membrane, enabling fusion and exchange with organelles or the cell surface.
3. Specialized Functions: Different vesicles store, transport, or digest cellular materials, helping maintain orderwithin the cell.

Key Characteristics of Vesicles

1. Membrane Composition
   1. The vesicle membrane is composed of a phospholipid bilayer, similar to the plasma membrane.
   2. This feature allows vesicles to fuse with other membranes, such as the plasma membrane or organelle membranes, facilitating material exchange.
2. Dynamic Nature: Vesicles are continuously formed and recycled, enabling cells to respond quickly to changing needs.
3. Specialized Functions: Vesicles transport materials, store substances, and even digest cellular debris.

Functions of Vesicles

1. Transport of Substances

1. Exocytosis: Vesicles carry materials (e.g., neurotransmitters, hormones) to the plasma membrane for secretion.
2. Endocytosis: Vesicles form by budding in from the plasma membrane to bring external materials (e.g., nutrients, pathogens) into the cell.
3. Intracellular Transport: Vesicles shuttle proteins, lipids, and waste products between organelles (e.g., rER → Golgi → lysosomes).

2. Membrane Growth and Maintenance

1. Delivery of Membrane Components: Vesicles transport phospholipids and membrane proteins synthesized in the rER to the plasma membrane, aiding cell growth and repair.
2. Organelle Function: Vesicles deliver enzymes and cargo to organelles like lysosomes, ensuring they functionproperly (e.g., in digestion or recycling cell components).