Unveiling the Wonders of Specialized Animal Cells & Functions| Cambridge IGCSE Biology

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Previously, we learnt about the basic structures of animal and plant cells. Whereas there are certain cells which share common features, there are some animal cells that are known as “specialised cells”.

These are cells that have a specific role or specific function in our body, and in order to ensure that this particular function is accomplished, they have a specific structure and unique characteristics.

How do cells become specialised?

Cells specialise through a process called differentiation. A new undeveloped cell will develop characteristics that are needed to carry out certain specific functions. Some new cells might become ciliated cells, others might become red blood cells, etc.

While there are many specialised cells in the animal body, what will be important in the context of the exam would be just five types of specialised cells.
1. Red Blood Cells (RBC)
2. Ciliated Cells
3. Sperm Cells
4. Egg Cells
5. Nerve Cells

1. Red Blood Cells (RBC)

Red blood cells are the most abundant type of cell found in our blood. When considering a pin drop of blood, it would contain about five million red blood cells. The reason for their abundance is the extremely crucial role they play in the lives of animals.

Red Blood Cells have one main purpose and that is to transport oxygen from the lungs to every single cell in our body. Red blood cells have four characteristics that make them the best suited for this job of transporting oxygen throughout the body.

a. Red Blood Cells contain Haemoglobin
Haemoglobin is a type of protein that is found in red blood cells. Oxygen can bind temporarily to this molecule and this helps the red blood cell to transport it around our body. Haemoglobin is therefore responsible for binding to the oxygen.
One reason that carbon monoxide in cigarette smoke, etc is poisonous to us is that haemoglobin is very receptive to carbon monoxide. With oxygen, haemoglobin only forms a temporary bond, but the bond with carbon monoxide is permanent, reducing the number of cells available to bind with oxygen.

b. Red Blood Cells do not have nuclei
A typical animal cell would have a nucleus, but red blood cells do not have nuclei. This is because not having a nucleus leaves more space in the cell to fit in more haemoglobin. Therefore, the more haemoglobin there is, the higher the oxygen carrying capacity.

c. Red Blood Cells have a biconcave shape
A biconcave shape is a disc shape with a thinner centre section (observe picture below). This unique shape maximises the surface area for oxygen diffusion, and red blood cells have better adapted this way for them to carry oxygen more efficiently.

d. They are very small and flexible
Red Blood cells need to carry oxygen to every single cell in our body, and this means they have to travel through the thinnest capillaries sometimes. With them being small and flexible, they can squeeze through the thinnest of these capillaries and deliver oxygen to every single cell that requires it.

Fun fact: The diameter of a red blood cell is about 0.000007 mm!

Red Blood Cell

2. Ciliated Cells

Ciliated cells are unique cells that are found in the respiratory tract in our trachea and bronchi, etc, and they have thin hair-like structures on them called “cilia”. Hence, they are referred to as ciliated cells.

These hair-like structures, or cilia, are always moving in a wave-like pattern, in coordination with one another. This leads us to the questions, why do these cells have cilia and why do they move? The reason these cells have cilia is because our respiratory tract is covered in mucus, and this mucus traps any unwanted particles from going into our lungs. The cilia move in coordination and sweep the mucus up along the surface of the respiratory tubes, so that it can be swallowed and safely digested.

Cilated cells

3. Sperm Cell

This is found only in males, and is the male gamete cell, therefore being involved in sexual reproduction and fertilisation.

The sperm cell has three parts to it; the head, the midpiece and the tail.

The head contains a nucleus which is a haploid nucleus (has only one set of chromosomes), and this contains the genetic material of the male animal. The midpiece contains mitochondria that creates energy the sperm cell needs to swim though the female reproductive tract. The tail is a mobile structure which can move about and help the sperm to swim.


The Acrosome:

There is an important structure found in the head of the sperm cell and this is known as the “acrosome”. The acrosome contains digestive enzymes and its function is to break through the wall of the egg cell and penetrate it so that the sperm cell can pass its genetic material on to the egg cell.


4. Egg Cell

This is the female gamete cell, and the egg cell is involved in sexual reproduction and fertilisation.

A unique feature of the egg cell is that it contains a lot of cytoplasm rich in nutrients. Once an egg cell gets fertilised, it will become an embryo. The cytoplasm in the egg cell has nutrients for the growth of the early embryo. And just like the sperm cell, this egg cell also contains a haploid nucleus containing the genetic material of the female animal (one set of chromosomes).

The cell membrane of an egg cell is also very unique. Once the egg is fertilised, the zona pellucida of the cell membrane hardens in order to prevent another sperm from entering it.


5. Nerve Cell

Nerve cells are found in the nervous system of animals. They are long cells, some of the longest actually, and they contain the basic parts of any animal cell, but the nerve cell is especially adapted to conduct nerve impulses very quickly. The nerves can run to and from different parts of the body, leading up to the central nervous system. These cells have extensions and branches to communicate with other nerve cells, muscles, and glands as well.

The final unique feature shown by nerve cells is that the axon of the nerve cell is covered with a fatty sheath made of myelin and called the myelin sheath. This insulates the nerve cell and speeds up the nerve impulses.


Revising Unveiling the Wonders of Specialised Animal Cells & Functions

Since this area relies heavily on diagrams, draw them and name each part carefully. Once exams draw near, you only have to quickly look through them to revise, and then refer to the functions of these cells.

Some questions on specialised animal cells and their functions can be found here as well, and you can time your answers to see if you can stick to the time limit given.

If you are struggling with IGCSE revision or Biology in particular, you can reach out to us at Tutopiya to join revision sessions or find yourself the right tutor for you.

Attempt the quiz to know where you stand!

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