Die Bilder - Prokaryotische Zelle-Struktur Und Funktion

Capsule Function in Prokaryotic cell

Function / September 24, 2018

A prokaryote is a simple, unicellular organism that lacks an organized nucleus or other membrane-bound organelle.

Learning Objective

  • Describe the structure of prokaryotic cells

Key Points

  • Prokaryotes lack an organized nucleus and other membrane-bound organelles.
  • Prokaryotic DNA is found in a central part of the cell called the nucleoid.
  • The cell wall of a prokaryote acts as an extra layer of protection, helps maintain cell shape, and prevents dehydration.
  • Prokaryotic cell size ranges from 0.1 to 5.0 μm in diameter.
  • The small size of prokaryotes allows quick entry and diffusion of ions and molecules to other parts of the cell while also allowing fast removal of waste products out of the cell.

Terms

  • nucleoid

    the irregularly-shaped region within a prokaryote cell where the genetic material is localized

  • prokaryotic

    Of cells, lacking a nucleus.

  • eukaryotic

    Having complex cells in which the genetic material is organized into membrane-bound nuclei.

Components of Prokaryotic Cells

All cells share four common components:

  1. cytoplasm: a jelly-like cytosol within the cell in which other cellular components are found

A prokaryote is a simple, single-celled (unicellular) organism that lacks an organized nucleus or any other membrane-bound organelle. We will shortly come to see that this is significantly different in eukaryotes. Prokaryotic DNA is found in a central part of the cell: the nucleoid .

Most prokaryotes have a peptidoglycan cell wall and many have a polysaccharide capsule . The cell wall acts as an extra layer of protection, helps the cell maintain its shape, and prevents dehydration. The capsule enables the cell to attach to surfaces in its environment. Some prokaryotes have flagella, pili, or fimbriae. Flagella are used for locomotion. Pili are used to exchange genetic material during a type of reproduction called conjugation. Fimbriae are used by bacteria to attach to a host cell.

General Structure of a Prokaryotic Cell

This figure shows the generalized structure of a prokaryotic cell.All prokaryotes have chromosomal DNA localized in a nucleoid, ribosomes, a cell membrane, and a cell wall.The other structures shown are present in some, but not all, bacteria.

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