Introduction to Cells

Study Notes

The cell is the basic structural, functional, and biological unit of all known organisms.
Cells are often called the "building blocks of life."
The study of cells is called cell biology, cellular biology, or cytology.

Cells have many parts, each with a different function.
The cell membrane (also known as the plasma membrane or cytoplasmic membrane) separates the interior of the cell from the outside environment.
The cell membrane is a biological membrane that encloses the protoplasm (the nucleus and the cytoplasm with its organelles and inclusions) and separates one cell from other cells and from the external environment.

The cell membrane is made of millions of smaller molecules that create a flexible and porous container.
The main components of the cell membrane are proteins and phospholipids.
Phospholipid molecules are shaped with a head and a tail region, where the head is hydrophilic (likes water) and the tail is hydrophobic (does not like water).
The lipid bilayer is formed by the arrangement of phospholipid molecules, with the hydrophobic tails facing inward and the hydrophilic heads facing outward.

There are three types of proteins in the plasma membrane:
- Integral proteins: embedded within the lipid bilayer, extending through the lipid bilayer to contact the interior and exterior of the cell.
- Peripheral proteins: attached to the exterior of the lipid bilayer, easily separable from the lipid bilayer.
- Lipid-bound proteins: located entirely within the boundaries of the lipid bilayer.
- Transport proteins (proteins channel): facilitate the transport of molecules across the membrane.

The plasma membrane separates the contents of the cell from its outside environment and regulates what enters and exits the cell.
It protects the integrity of the interior of the cell by allowing only selected substances into the cell and keeping other substances out.
It serves as a base of attachment for the cytoskeleton in some organisms and the cell wall in others.
The cell membrane supports the cell and helps in maintaining the shape of the cell.