Name: inside prokaryotic cell structure
Uploaded: 2020-11-23T11:47:33.000Z
Duration: 1 min 51 s
Channel: JoVE

Prokaryotes include archaea and bacteria, which are simple, unicellular organisms that lack membrane-bound organelles.These cells are surrounded by a selectively permeable plasma membrane that encloses the cellular contents within a gel-like cytoplasm.An additional protective layer called the cell wall surrounds the plasma membrane. In bacteria that possess a cell wall, it is made of peptidoglycan, a polymer of amino acids and sugars, and helps maintain cell shape and internal osmotic balance. In archaea, the cell wall does not contain peptidoglycan and is composed of other materials, such as proteins or polysaccharides.Some bacteria also have a capsule, which is a polysaccharide layer that promotes adhesion to surfaces and provides protection.Inside the cell, typically a single circular DNA molecule is located in a region called the nucleoid. This DNA is not enclosed within a membrane.Many prokaryotes also contain smaller circular DNA molecules called plasmids, which replicate independently and can be transferred between cells. These plasmids can also carry genes that provide adaptive advantages, such as antibiotic resistance.Although prokaryotes lack membrane-bound organelles, some species contain specialized internal structures. For example, cyanobacteria have carboxysomes and thylakoids that enable photosynthesis.Prokaryotic cells have limited internal compartmentalization and can survive in diverse and sometimes extreme environments.

prokaryotic cells

Prokaryotes are small unicellular organisms that include the domains&#x2014;Archaea and Bacteria. Bacteria include many common organisms, such as Salmonella and E. coli, while the Archaea include extremophiles that live in harsh environments, such as volcanic springs.Like eukaryotic cells, all prokaryotic cells are surrounded by a plasma membrane, have genetic material in the form of single, circular DNA, a cytoplasm that fills the interior of the cell, and ribosomes that synthesize proteins. However, unlike eukaryotic cells, prokaryotes lack a nucleus or other membrane-bound intracellular organelles. Their cellular components float freely within the cytoplasm, although their DNA is clustered within a region called the nucleoid.Inside the cytoplasm, many prokaryotes have small, circular, double-stranded pieces of DNA called plasmids. These are distinct from the cell&#x27;s chromosomal DNA and carry just a few special genes that provide bacteria with survival advantages, such as antibiotic resistance. Plasmids are self-replicating and can be transmitted between prokaryotic cells.Most prokaryotes have a cell wall made of peptidoglycan that lies outside of their plasma membrane. It physically protects the cell and helps it maintain osmotic pressure in different environments. Many prokaryotes also have a sticky capsule layer that covers their cell wall and allows them to stick to a substrate or each other, thus providing additional protection.While prokaryotes do not have membrane-bound organelles, some have infoldings of the plasma membrane that carry out specialized functions&#x2014;such as photosynthesis in cyanobacteria. Therefore, although prokaryotes are simple cells compared to eukaryotes, they do have some unique structures that help them carry out complex functions and allow them to live in a wide variety of environments.

Prokaryotic cells

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Education

JoVE Core

Molecular Biology

Unit 1

DNA, Cells, and Evolution

KEY TERMS AND CONCEPTS

inside prokaryotic cell structure

Prokaryotic cells have a simple internal structure compared with many other cells. They are usually divided into two groups: bacteria and archaea. These cells have no nucleus, so their DNA is not enclosed in a membrane-bound compartment.

Instead, the genetic material is found in the nucleoid, a region where the DNA is located in the cell. Some prokaryotic cells also contain plasmids, which are small extra DNA molecules. A capsule may surround the cell and provide an additional outer layer.

This page focuses on the main features that help identify prokaryotic cells. Those features include the nucleoid, plasmids, and capsule. Together, they show how prokaryotic cells are organized and how they differ from more complex cells.

Inside Prokaryotic Cell Structure

the dna helix

DNA Structure and Base Pairing

DNA has a helical structure that helps store genetic information. The double helix is the shape formed by two strands that twist around each other. This structure is a key feature of DNA in cells. The two strands are held together by base pairing. Bases on one strand match with bases on the other strand in a regular way. This pairing helps keep the DNA molecule stable and organized. The helix shape also helps explain how DNA fits into chromosomes and carries instructions for living things. By...

the central dogma

DNA to Protein: Central Dogma Steps

The central dogma explains how genetic information moves from DNA to RNA to protein. This flow is a key idea in molecular biology. It helps show how cells use genes to make the molecules that carry out work. DNA stores the instructions for making proteins. During transcription, a gene in DNA is copied into RNA. The RNA then carries that message to the next stage. In translation, the RNA message is used to build a protein. Proteins do much of the cell’s work, so this process connects genes to...

Prokaryotic cells have a simple internal structure compared with many other cells. They are usually divided into two groups: bacteria and archaea. These cells have no nucleus, so their DNA is not enclosed in a membrane-bound compartment. Instead, the genetic material is found in the nucleoid, a region where the DNA is located in the cell. Some prokaryotic cells also contain plasmids, which are small extra DNA molecules. A capsule may surround the cell and provide an additional outer layer. <br...

eukaryotic compartmentalization

Cell Compartments in Eukaryotes

Eukaryotic cells use compartments to organize many different jobs inside one cell. These compartments help separate processes so they can happen in the right place. The compartment called the cytosol is the fluid part of the cell. It surrounds the other internal structures and helps support many cell processes. Inside the cell, membrane-bound organelles create distinct microenvironments. A microenvironment is a small internal space with conditions that fit a specific task. This separation...

the tree of life - bacteria, archaea, eukaryotes

the-tree-of-life-bacteria-archaea-eukaryotes

How Life Is Classified Into Three Domains

The tree of life shows how organisms are related through evolution. Its root represents the common ancestor of all life on Earth. From that point, branches spread out like a tree. The tips of the branches represent living, or extant, species. Species that no longer exist, called extinct species, appear closer to the center of the tree. Today, these organisms are grouped into three domains: bacteria, archaea, and eukaryotes. Scientists still debate these divisions, so the tree of life keeps...

mutations

How Mutations Change DNA

Mutations are changes in DNA. They can alter the genetic code and affect how genes work. In high school biology, students often study mutations to understand how DNA changes can influence traits. The transcript focuses on two common mutation types: point mutations and frameshift mutations. A point mutation changes one nucleotide, which is one DNA building block. A frameshift mutation happens when nucleotides are added or removed and the reading frame shifts. These changes matter because they...

gene evolution - fast or slow?

Why Some Gene Regions Evolve Faster

Gene regions do not all change at the same rate. In eukaryotes, long stretches of DNA do not code for proteins or RNAs. Some of these non-coding regions include important regulatory sequences, but most have no known function. Because little or no selection pressure acts on them, they often change the fastest over evolutionary time. Protein-coding regions usually evolve more slowly. A change in a coding sequence can alter a protein and make it less effective at doing its job. That creates...

genome size and the evolution of new genes

genome-size-and-the-evolution-of-new-genes

How Genome Size Shapes New Genes

Genome size can vary widely, and it also helps show how new genes form. Every living organism has a genome, whether it uses RNA or DNA. Yet the size of that genome can be very different from one organism to another. One major difference is whether the organism is prokaryotic or eukaryotic. Prokaryotic genomes usually have little to no non-coding sequence, which means genes are packed closely together in operons along the chromosome. Eukaryotic genomes contain long stretches of non-coding DNA...

gene families

How Gene Families Evolve and Diversify

Gene families are groups of genes that are thought to come from a shared ancestor. They usually form when a gene is copied by mistake during cell division. The original gene stays under selection pressure to keep its job, while the extra copy can change more quickly over time. Some copied genes gain a new role in the organism. When that happens, they are called paralogs, which are two genes in the same species that evolved from one common ancestral gene. Gene families also include orthologs,...

types of genetic transfer between organisms

types-of-genetic-transfer-between-organisms

How Genes Move Within and Across Generations

Genetic transfer is the movement of genetic information from one organism to another. It happens in two main ways: vertical gene transfer and horizontal gene transfer. Vertical gene transfer moves genes from one generation to the next. It is much more common than horizontal gene transfer. Vertical gene transfer happens during both sexual reproduction and asexual reproduction. In both cases, one or more organisms pass some or all of their genome to their offspring. This kind of transfer occurs...

key terms and concepts

Explore the structure of prokaryotic cells, including the nucleoid, plasmids, and capsule, and see how bacteria and archaea are organized.

Inside Prokaryotic Cell Structure | JoVE K12

molecular biology

JoVE Core Molecular Biology showcases the molecular processes of the cell through clear and concise animated video lessons. Additionally, in scientist-in-action videos, these concepts' application is demonstrated through real experiments in modern laboratories.

Inside Prokaryotic Cell Structure

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