Fundamentals

Cell biology is the study of cell structure and function. It helps in the understanding of disease processes as every disease ultimately starts at the cellular level. The ever evolving knowledge of cell biology can be utilized to develop more effective, personalized and safer therapies. A human cell is composed of the nucleus, cytoplasm that contains organelles and a cell membrane that surrounds it.

1. Cell or plasma membrane: It is a double layer of phospholipid molecules interspersed with protein molecules that provide structural support, help in cell-to-cell adhesion, form channels for passage of materials, act as receptor sites and function as carrier molecules. The phospholipid bi-layer has a hydrophobic core and hydrophilic ends and forms an effective diffusion barrier. Cell membranes contain a mix of saturated and unsaturated phospholipids, with the latter type making the cell membrane more fluid at body temperatures. Cell membranes differ in the types of phospholipids. The cell membrane acts as a barrier separating the intracellular from extracellular components, maintains the integrity of a cell, maintains ion gradients and controls passage of materials into and out of the cell. The intracellular environment or cytosol is electronegative compared to the external environment. Ion gradients are essential for transmission of signals like in the nerves and conducting tissues of the heart and to regulate the activity of intracellular enzymes.

Cell membrane associated proteins can be either integral or peripheral. Integral proteins are permanently embedded in the membrane and they form channels, receptors and adhesion molecules. Peripheral proteins are transiently attached to the cell membrane and provide structural support, transmit cellular signals and help with secretory function.

Important features of cell organelles