Prokaryotic cell explained with its structure

len Alfred Ajibola - 04th July, 2023 @ 09:21 AM

Topics in Biology

Difference between plant cell and animal cell Nucleus explained with its structures Nucleus explained with its types and functions Organelles of the cell explained with their characteristics Eukaryotic cell explained with its characteristics Prokaryotic cell explained with its structure Characteristics of prokaryotic cell Concept of cell Cell theory in biology Importance and limitations of ecological pyramid Protists explained with their characteristics Contents of the scrotum: Epididymis, vas deferens, spermatic cord and cremaster muscle Tropical savanna explained with its characteristics Concept of ecological pyramid Hindbrain: Medulla Oblongata and its features Food web explained with examples Biology Scheme of Work, SS1, First Term Biology Scheme of Work, SS1, 2nd Term Biology Scheme of Work, SS1, 3rd Term Male accessory sex organs: Seminal vesicles and bulbourethral glands

Academic Questions in Biology

Please click here to see all Questions and Answers

Male Reproductive System - Len Academy

From the above diagram, which of the organ below isn't a requirement for the male reproductive system?

  • A. Bladder

  • B. Ureter

  • C. Glans Penis

  • D. Testis

  • E. Bulbourethral Gland

  • F. Epididymis

A walnut shaped male accessory sex organ located between the bladder and penis is the _____.

  • A. Ductus Ejaculatorii

  • B. Bulbourethral Gland

  • C. Prostate Gland

  • D. Ductus Deferens

  • E. Seminal Vesicles

  • F. Epididymis

In a food chain, the primary consumers are classified under trophic level  _____.

  • A. Zero

  • B. One

  • C. Two

  • D. Three

  • E. Four

  • F. Five

Cold blooded animals are referred to as _____.

  • A. Homeotherms

  • B. Endotherms

  • C. Poilokitherms

  • D. Ectotherms

  • E. Thermotherms

  • F. None of the above

All reptiles are vertebrates.

  • A. True

  • B. False

_____ cells are responsible for the formation of osteoblasts.

  • A. Osteocytes
  • B. Chondrocytes
  • C. Chondroblasts
  • D. Osteoclasts
  • E. Osteoprogenitor cells
  • F. Osteoblastic

_____ is a bone that constitute the axial skeleton.

  • A. Clavicle
  • B. Scapula
  • C. Patella
  • D. Radius
  • E. Sternum
  • F. Femur

Which of the following is false concerning cartilages and bones?

  • A. Cartilage does not have a direct blood supply while bones have direct blood supply
  • B. The process of ossification replaces a cartilage to bone
  • C. The protein that makes up cartilage is called chondrin while that that makes up bone is called ossein
  • D. Cartilage grows from both ends while bones grow from one of its epiphysis
  • E. They both have living cells within them
  • F. Haversian system is absent in cartilage but present in bones

Prokaryotic Cell:

Recall that a cell is defined as the basic, structural and functional unit of life.

Generally, cells are put into two types based on the presence or absence of a well-defined nucleus within it, alongside their specific setups. These are:

  1. Prokaryotic Cell 

  2. Eukaryotic Cell
    Please read on eukaryotic cell explained with its characteristics here.


Prokaryotic cells (or prokaryotes) are unicellular organisms lacking a definitive nucleus. They have a cell size ranging from 0.1 to 0.5 µm (micrometer) in diameter, and are typically in the domain of archaea, cyanobacteria and bacteria. Generally, prokaryotes are found everywhere on earth, be it on land, water and air, including inside living organisms.

Please read an introduction to cell here.


The prokaryotes 'archaea' are ancient organisms that thrive under extreme conditions. As an instance, Pyrolobus fumarii is an archaea that lives in hydrothermal vents with temperatures around 113 oC or 235 oF.

The Picrophilus are another group of archaeans that live in soils with an acidic pH as low as zero. In fact, they are the most acid-tolerant organisms known on earth.

The methanogens are another group of archaeans found in places without oxygen (anaerobic environment) such as hot springs, intestines of animals and marshes. Such methanogens include Methanobrevibacter gottschalkii, Methanococcus maripaludis, Methanogenium frigidum, Methanopyrus kandleri, Methanosaeta concilii, Methanosarcina barkeri, and Methanosphaera stadtmanae.

Please read on swamp forest here.


Cyanobacteria are prokaryotes, and were formerly termed as blue-green algae. They are known to manufacture their own food through a process termed photosynthesis. They are able to do this as a result of the green pigment (chlorophyll) present within their cell. They constitute a large number of the aquatic ecosystem, that is: oceans, seas, rivers, lakes and ponds respectively.

Please read on photosynthesis and chemosynthesis here.


Bacteria are considered as one of the most popular prokaryotes on earth due to their harmful and beneficial actions to other organisms. For instance, numerous beneficial bacteria are present in the colon of humans and ruminants. However, some could be harmful; for example, certain strains of Escherichia coli (E. coli O157:H7) present in the intestines of animals.

Note: the population of bacteria inside the human body is higher than the total number of human beings living on earth.

You can read interesting facts for students here.


  • The existence of prokaryotes had been dated back to over five billion years. Interestingly, fossil fuels had shown the existence of prokaryotes, and it is believed by scientists that they metamorphosed into various forms of life existing on earth.

    Please read on ecological concepts here.


Prokaryotic Cell - Len Academy

Prokaryotic Cell


Structure of a Prokaryote

The above image will serve as a reference towards the explanation on various structures of a prokaryotic cell.

The prokaryotic cell is bounded by a plasma membrane (or cell membrane), cell wall and an outermost capsule. The cell membrane is semipermeable. This means that it can allow the entry and exit of certain substances, while denying others. Also, it can be utilized for respiratory activities.

Please read the characteristics of living organisms here.

The cell wall is present just after the cell membrane and before the capsule. It is made up of peptidoglycan (or murein), which is a polymer of sugars and amino acids. It functions to protect the cell from unfavorable external conditions, prevents it from bursting, and also gives the prokaryotic organism its shape.


Alongside the cell wall, an outer protective layer called capsule may also be found in the cells of bacteria. They are formed from capsular polysaccharides (CPSs) with varying structures. The capsule functions to preserve and protect the cell form being digested or dissolved (through phagocytosis) by enzymes or other foreign cells. Together with the slime layer, it aids the attachment of the bacteria to nutrients and adjacent cells. Meanwhile, understand that the capsule have also got good water retention ability.

You can read amazing facts in biology here.


Prokaryotic cell do not have a definite nucleus, neither do they have nuclear membrane. They have a chromosomal Deoxyribonucleic Acid (DNA), typically present on a single chromosome. Such DNA is crucial for their sexual reproduction. However, they may also have non-chromosomal DNA materials called plasmids, and these are not required in reproduction. The location of the prokaryotic genetic materials are somewhere in a cytoplasmic region termed as nucleoid, and this could be spiral, spherical, rod-like or irregular in shape.

The nucleoid in prokaryotes is the region in the cytoplasm where genetic material is located.

You can read on the contents of the scrotum in humans here.

Note: Plasmids are non-chromosomal DNA structures in prokaryotes. As a result, they are not involved in reproduction.


Prokaryotic cells often have pili. These are short proteinous hairlike structures used for attachment to the surface of other cells. They may be utilized for the cell's movement, but more importantly, they initiate the infectious and virulent properties of harmful bacteria. However, some prokaryotes may also have a whiplike structure called flagella which serves locomotary purposes for the cell.

The appendages for locomotion are called protrusions, and are often found on the surfaces of prokaryotic cells. They include flagella, fimbriae and pili.

You can read on protists explained with their characteristics here.

  • Sex pili may also be present in prokaryotes, and are utilized for DNA exchange.


The cytoplasm is a gel-like fluid filled space within the plasma membrane of a prokaryotic cell. It is composed mainly of cytosol, ribosomes, inclusions, cytoskeleton, enzymes and salts.

The mitochondria, golgi apparatus and endoplasmic reticulum are all absent in prokaryotes. However, ribosomes may be present, and are involved in protein synthesis.

You can attempt Len Academy questions on various subjects here.


Reproduction in prokaryotes can occur either sexually or asexually. Asexual reproduction is typically through a process termed binary fission, while sexual reproduction occurs through gene recombination.

Gene recombination in prokaryotes can be achieved via the following methods:

  1. Conjugation

  2. Transformation

  3. Transduction
    Please read on the characteristics of prokaryotes alongside their reproduction here. here.

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Pufferfish contain a toxin called tetrodotoxin. This makes them foul tasting and poisonous to predators. Tetrodotoxin is about 1,200 times more poisonous than cyanide, and there is enough toxin in one pufferfish to kill 30 adult humans. Unfortunately, there isn't any known antidote to this poison.

Interestingly, a delicacy in Japan (called fugu) is made from pufferfish. This meal is very expensive, and must be prepared by trained and licensed chefs. An improper preparation of fugu may lead to the customer's death. Sadly, such deaths are recorded annually

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Robert Wadlow (1918–1940) remains the tallest man ever recorded in the Guinness World Records. He was an American who stood at 8 feet, 11 inches.

An abnormally enlarged pituitary gland had resulted into Robert Wadlow's giant size.

Cockroach is the fastest land animal on six legs

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Notable points in Biology

Layers of an Artery - Len Academy

An artery is composed of three layers:

  • The outermost layer is termed tunica adventitia (or tunica external). It consist mainly of collagen fibres and connective tissues that anchors the arteries to other nearby tissues.

  • The middle layer is named tunica media. It is made up of smooth muscles and elastic fibres that supports the artery in conveying blood at high pressures.

  • The inner layer is called tunica intima (or tunica internal). It is lined by a smooth tissue called endothelium, and is made up of a fine network of connective tissues.

Please read on the layers of an artery here

All living organisms possess various features in order to survive in their environment. This is the concept of adaptation. As an instance, a fish is able to live in water because it has gills and fins.

Also, a camel is able to survive in the desert because it has large feet to aid walking on sand without sinking. It also has long eyelashes to help protect it from the blowing sand and wind.

Plants are also able to live in different habitats because they have the required adaptive features towards that habitat. For instance:

  • Plants that live in/on water are termed hydrophytes.

  • Plants that live on land with moderate amount of water are termed mesophytes.

  • Plants that live on deserts or arid lands are termed xerophytes.

The point is:

All organisms have various features on them that enables them adapt in their habitat

For a thing to be considered living, it must possess all the basic characteristics of life. These include:

  1. Movement

  2. Respiration

  3. Nutrition

  4. Irritability or Sensitivity

  5. Growth

  6. Excretion

  7. Reproduction

  8. Death

  9. Adaptation

  10. Competition

Please read the explanations on all the basic characteristics of life here

During strenuous exercises like sprinting or running, your body may actually work in the shortage of oxygen. During this time, your body owes oxygen (called oxygen debt) and it must be replenished or repayed after the exercise is stopped. This is why you breathe excess of oxygen after you stopped the exercise.

This is the concept of anaerobic respiration

Food Chain - Len Academy

A food chain is a diagram that shows the relationship between plants and animals within a habitat on the basis of how they rely on each other for food.

Note: Habitat is a place where an organism live. It is of three types:

  • Terrestrial (Land)
  • Aquatic (Water)
  • Arboreal (Treetops)

You can read on food chain here