The Eukaryotic Cell

This sketch of a eukaryotic cell is modeled after illustrations in Hickman, et al. and Audesirk& Audesirk. It is intended to show the types of organelles in cells, although no single cell is expected to have all these organelles.

Typical quoted numbers for cells in the human body are in the 10s of trillions, or in excess of 10 trillion or 10¹³. This on the order of a hundred times the estimated 200 billion or 2 x 10¹¹ stars in our galaxy.

Types of Cells

Living things are made up of distinct units called cells. Multicellular animals including humans are made up of complex cells with multiple internal organelles. These cells are called eukaryotic cells. Single cell organisms are often referred to as microbes. Single-celled organisms like bacteria are examples of prokaryotic cells. There are other prokaryotic cells which exhibit enough differences from bacteria to be classified as a separate Domain Archaea or the Archaebacteria.

All cells have genes, organelles, a cell membrane, and cytoplasm.

Eukaryotic Cells

Most of the life that is visible to the naked eye is made up of eukaryotic cells. These cells are characterized by a membrane-bound nucleus, and many eukaryotic cells have multiple membrane-bound organelles to carry out specific cell tasks. Eukaryotic cellular life is broken up into four kingdoms: protista, fungi, plants and animals.