Concept of cell

len Alfred Ajibola - 26th June, 2023 @ 01:56 PM

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

Introduction to Cell:

All living organisms share one thing in common, and that's the cell. In this regard, a cell is defined as the fundamental, basic, structural and smallest unit of life. You can consider cells as the building blocks of life, and they come in different shapes and sizes. Simply put, life commence from the cell.


  • The study of cells in its entirely is called cell biology. In fact, students could choose to further their education by delving into this broad field of biology. It was the development of microscope that opened up the world of cell to various scientist.

  • Please read the cell theory here.


From the above introduction, it can be inferred that anything that has life must consist of one or more cells. As an instance, a bacteria is considered a living organism even though it consist of only one cell (unicellular). Similarly, human beings are considered as living organisms because they also consist of cells. However, they consists of more than one cell, and are said to be multicellular. In fact, humans are made up of trillions of cells.

Meanwhile, understand that multicellular organisms can be typically seen with the naked eyes.  They include most plants and animals.

Please read on the basic characteristics of living organisms here.


Viruses doesn't exist at the cellular level of life, and this has brought some division among scientists as to whether they are living organisms or not.

Meanwhile, understand that viruses do no exhibit the basic characteristics of life outside a living organism, and are thus considered as non-living in this regard. On the other hand, if they are introduced into a living environment (for instance, the human respiratory system), they tend to carry out some basic characteristics of life like reproduction and mutation, and are thus considered as living in this instance.

Viruses are considered by some scientist to exist in the borderline of life.

Please read on protists here.


A single-celled organism is termed unicellular. They are generally very small and can't be seen with the eyes alone. Since they can only be seen with the aid of a microscope, they are appropriately termed microscopic organisms. Example of unicellular organisms include bacteria, protist and some fungi.

The smallest known cell is the Mycoplasma gallicepticum. It has a size of about 10 micrometer. They cause respiratory infections in chicken and turkey.

Read interesting facts for students here.

Mycoplasma gallicepticum - Len Academy

Mycoplasma gallicepticum


Life processes are controlled through the proper functioning of the cell. Using humans as a point of reference, brain defects can be attributed to the malfunctioning and necrosis (death) of the cells comprising it. When this happens, the functioning of the brain is impaired. This could ultimately lead to the death of the victim if not treated appropriately.

You can read an introduction to the human brain here.

Still using humans as a point of reference, every part of our body (from the top of our hair to the sole of our feet) are made up of cells. However, these cells are quite different in functions depending on their location. For instance, the cells making up the brain are quite different from those present in the eyes. Similarly, the cells comprising the liver have an entirely different function from those present in the reproductive organs.

Please read on the male reproductive system here.


Cells can become grouped together, giving rise to tissues. A tissue is a group of cells that have similar structure, and they function together as a unit.

In multicellular organisms, tissues are cells with similar structure, and grouped together, and as such work as a unit by carrying out a similar or specific function.


There are four types of tissues in the human body. These are:

  1. Connective Tissue: They support other tissues by linking them together. Examples are blood, bones, cartilage and lymphatic tissue.
    Please read on the bones of the human skeleton here.

  2. Epithelial Tissue: They provide linings to the skin, respiratory tract, intestine and abdominal cavity.

  3. Muscular Tissue: Examples are striated, skeletal or voluntary muscles that support the movement of bones. We also have smooth, unstriated or involuntary muscles that line the intestinal tract and blood vessels. Cardiac muscle is found in the heart, aiding its contraction and eventual pumping of blood.
    You can read on arterial disorder here.

  4. Nervous Tissue: These are neurons, and are present in the brain and spinal cord.
    Please read on the cerebrum here.


Cells contain various components that aid in its functioning as a unit. These are termed organelles. Some of these organelles are suspended (or floats) within a fluidy environment (termed cytoplasm) inside the cell.

The diagram below shows the structure of the cell and its organelles:

Cell structure and organelles - Len Academy


Below are organelles present in the cell:

  • Cell membrane

  • Cell wall

  • Mitochondria

  • Nucleolus

  • Nucleus

  • Ribosome

  • Rough Endoplasmic Reticulum

  • Smooth Endoplasmic Reticulum

  • Golgi apparatus

  • Cytoskeleton

  • Cytosol

  • Lysosomes

  • Centriole

  • Peroxisome

  • Centrosome

  • Vesicles

  • Large central vacuole

  • Small and scattered vacuoles

  • Chloroplast

  • Cilia

  • Flagella


Cells can generally be put into two types, and these are dependent on whether they have a definite nucleus or not. They are:

  1. Prokaryotic Cell

  2. Eukaryotic Cell

Kindly share this article via the links below:


Click here to read on Len Academy Smart School Software. Contact us for a standard website at an affordable price

Please click here to follow Len Academy on Google News.

Please Register here or Login here to contribute to this topic by commenting in the box below.

Amazing facts in Biology

Russia is home to the largest area of forest in our world with a land mass of 815 million hectares

Giant Squid - Len Academy

Giant squid lives deep in the ocean and they have the largest eyes in the world

The movements of the fingers are controlled by muscles of the palms and forehands

Platypus - Len Academy

Platypus (sometimes referred to as the duck-billed platypus) is an egg-laying, semiaquatic mammal found in eastern Australia. It has no stomach and as such, its food goes from the mouth through the esophagus and directly to their intestines.

Pufferfish - Len Academy

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

Wombat - Len Academy ​​​​​​

Wombats are the only animal with a cube-shaped poo. They can stack up these cube-shaped poo, marking their territory with it

Robert Waldow - Len Academy

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

Laughing ape - Len Academy

Like humans, all apes laugh when tickled

Ostrich eye and brain - Len Academy

An ostrich's eye is bigger than its brain

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