What's Inside the Cell?

Overview of Cell Structure

Cells are the fundamental units of life, and their internal structures determine their function and classification. There are two broad groupings of life based on cell structure: Prokaryotes and Eukaryotes. Additionally, evolutionary history divides prokaryotes into Bacteria and Archaea, with Eukarya as the third domain.

• Prokaryotes: Cells lacking a membrane-bound nucleus.

• Eukaryotes: Cells possessing a membrane-bound nucleus.

• Domains: Bacteria, Archaea (both prokaryotic), and Eukarya (eukaryotic).

Prokaryotic Cells

Characteristics of Prokaryotic Cells

Prokaryotic cells are structurally simpler than eukaryotic cells. They are found in the domains Bacteria and Archaea.

• Plasma Membrane: Surrounds the cytoplasm and regulates the movement of substances in and out of the cell.

• Cytoplasm: The internal fluid containing all cellular contents.

• Internal Structure: Few or no substructures separated by internal membranes; most metabolic processes occur in the cytoplasm.

• Cell Wall: Provides protection, shape, and structural support. In bacteria, the cell wall is primarily composed of peptidoglycan.

Key Terms

• Prokaryote: An organism whose cells lack a nucleus and other membrane-bound organelles.

• Cytoplasm: The jelly-like substance within the cell membrane that contains all organelles and cell parts.

• Cell Wall: A rigid layer outside the plasma membrane, providing structural support and protection.

Examples and Applications

• Bacteria: Escherichia coli (E. coli) is a common prokaryotic cell studied in biology.

• Archaea: Often found in extreme environments, such as hot springs and salt lakes.

Comparison Table: Prokaryotic vs. Eukaryotic Cells

Additional info: The first image shows a fluorescent micrograph of a eukaryotic cell, highlighting the nucleus (blue), cytoskeleton (green), and other cellular structures (red). The second and third images are lecture slides introducing the topic and summarizing prokaryotic cell characteristics.