Prokaryotic cells have a plasma membrane around them, but no internal membrane-bound organelles within their cytoplasm. The absence of a nucleus and other membrane-bound organelles distinguishes prokaryotes from eukaryotes, another class of creatures. While the majority of organisms on Earth are composed of cells that contain nuclei, some bacteria can be seen without any nuclear content under the microscope.
Bacteria don't have nuclei because they're prokaryotes, which means they don't have any kind of enclosed structure within their cells that contains DNA. Instead, each bacterial cell contains a small number of large structures called nucleoids. The nucleoids consist mainly of DNA wrapped around protein cores, but they also include other cellular components such as RNA. Proteins produced by genes on these nucleoids control what genes are expressed and how long it takes for new proteins to be made.
Even though bacteria don't have nuclei, they do still divide into two new cells during division. This process requires them to make lots of new proteins, so they depend on gene expression controlled by proteins such as repressors and activators to make sure only necessary genes are turned on at any one time. For this reason, bacteria must keep their nucleoid contents separate until the right time to divide occurs.
The majority of prokaryotes are single-celled creatures with a basic structure. Instead, the cell contains a nucleus that controls the expression of genes which produce proteins essential for survival. Proteins are then produced by these genes, used by the cell to build itself new parts, and then destroyed when they are no longer needed. Some bacteria do have small portions of DNA that control certain aspects of gene expression, but not enough to fully replicate themselves. These "plasmids" can be passed on to future generations by means of transference via conjugation or through viruses.
In addition to being single-celled, prokaryotes are also non-viable (or "dead"). This means that they cannot grow or reproduce independently - they need a living organism to survive in. However, some prokaryotes can switch into a viable but not culturable state in which they still contain all of their genetic information but cannot grow because they are trapped inside a protective protein shell called a vesicle. When conditions change, such as when more oxygen is available or when nutrients are added to the medium, the vesicles break open and the prokaryotes recover their ability to live.
Prokaryotes are unicellular creatures that lack membrane-bound components such as the nucleus. Prokaryotic cells are tiny, basic cells that range in size from 0.1 to 5 mm in diameter. Prokaryotic cells lack membrane-bound structures but do contain discrete cellular areas. These areas contain different types of organelles including mitochondria for energy production, ribosomes for protein synthesis, and chloroplasts where photosynthesis takes place. Prokaryotes are classified according to their morphology and the complexity of their genetic material.
Eukaryotes are organisms that have evolved into more complex forms with distinct membranes. Eukaryotic cells can be very large; for example, some bacteria grow so rapidly that they divide in just minutes instead of hours or days. However, most eukaryotes are smaller than prokaryotes because they need not be as efficient or effective at reproducing themselves. For example, humans can live for many years without eating or drinking because we have evolved to require less physical activity and stress under ordinary circumstances. In addition, our immune systems function well enough to keep us healthy even when we are infected with viruses or bacteria.
Eukaryotic cells usually contain a nucleus, which consists of chromatin (a complex mixture of DNA and proteins) surrounded by a membrane. Inside the nucleus are genes, which are regions of DNA that control what type of proteins are made from mRNA.
The primary difference between prokaryotes and eukaryotes is that prokaryotes lack membrane-bound organelles. They lack mitochondria, the Golgi apparatus, and the endoplasmic reticulum. They do not have a membrane-bound nucleus, but they do have genetic material in a nucleoid area. This area may be visible under the microscope as a dense region of chromatin.
Prokaryotes are simple organisms with no special structures beyond the plasma membrane and the cytoplasm. The plasma membrane allows them to divide and give rise to new cells while eukaryotes need to keep this process under control. For example, without any special structure like a nucleus, prokaryotes cannot reproduce themselves by dividing into two identical daughter cells. Instead, their plasma membranes split apart and move away from one another so that each daughter cell receives a single membrane.
Without mitochondria, prokaryotes are not able to produce energy through oxidative phosphorylation. They must get their energy from other sources such as chemicals produced by photosynthesis or by eating other microorganisms. Some prokaryotes can also obtain energy from the chemical oxidation of sulfur compounds or nitrogen compounds but these processes are less common.
In conclusion, prokaryotes lack organelles within their cells that eukaryotes possess.
Prokaryotes are significantly smaller than eukaryotes. Eukaryotes are distinguished by their membrane-bound organelles, which include mitochondria, vesicles, and vacuoles. Organelles that are membrane-bound do not exist in prokaryotes. Instead, the plasma membrane is folded into a variety of shapes to create cavities within the cell.
Bacteria can be divided into two groups on the basis of size: Gram-positive bacteria, which contain their DNA in a nucleus located in one part of the cell; and Gram-negative bacteria, which have their DNA in a nucleus located in one part of the cell with an outer membrane surrounding the rest of the cell.
Viruses are microscopic particles that contain RNA or DNA. They cannot replicate themselves and therefore depend on other organisms for reproduction. There are three main types of viruses: lytic, latent, and retroviruses.
Lytic viruses completely destroy their host cells and release new viruses into the environment so that they can find new hosts. The only virus we are aware of that produces lytic infections is the herpes virus. It forms bubbles of fluid called phagosomes within infected cells, which eventually rupture releasing more viruses into the cytoplasm.
Latent viruses infect host cells without killing them, instead using the host's immune system to protect itself.