A prokaryotic cell is a cell that lacks a nucleus and other membrane-bound organelles. Bacteria and Archaea are prokaryotes, and they are predominantly single-celled organisms. In a prokaryote, DNA is located in a central region called the nucleoid; it is not enclosed within a membrane-bound nucleus.
Bacterial cells have a cell wall made of peptidoglycan, a material composed of sugars and amino acids. The wall helps protect the cell, maintain its shape, and prevent dehydration. Many bacteria also have a polysaccharide capsule, which can help the cell attach to surfaces. Unlike bacteria, Archaea do not have cell walls made of peptidoglycan.
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What distinguishes a prokaryotic cell from a eukaryotic cell?
A prokaryotic cell lacks a membrane-bound nucleus and other membrane-bound organelles. A eukaryotic cell has a membrane-bound nucleus and specialized membrane-bound organelles.
What is the nucleoid?
The nucleoid is the central region of a prokaryotic cell where its DNA is found. It is not surrounded by a membrane.
What are the functions of a bacterial cell wall and capsule?
The peptidoglycan cell wall helps protect a bacterium, maintain its shape, and prevent dehydration. A polysaccharide capsule, found in many bacteria, can help the cell attach to surfaces.
What are flagella and pili used for in some prokaryotes?
Flagella are used for locomotion. Most pili are used to exchange genetic material during conjugation.
How does cell size affect material transport?
Small prokaryotic cells allow materials to spread through the cell and wastes to leave quickly. As cells grow, volume increases faster than surface area, making transport across the cell surface more challenging.
Quiz questions
Which four components are found in all cells?Answer: A plasma membrane, cytoplasm, DNA, and ribosomes.
Where is DNA located in a prokaryotic cell?Answer: In a central region called the nucleoid, outside a membrane-bound compartment.
What material makes up the cell wall of bacteria?Answer: Peptidoglycan, a material composed of sugars and amino acids.
A prokaryote uses an external structure to move through its environment. Which structure is it most likely using?Answer: A flagellum, which supports locomotion.
Why can a large cell have difficulty acquiring enough materials for its internal processes?Answer: Its volume increases faster than its surface area, reducing surface area relative to volume.
Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.