This article covers the remarkable and exceptional features that are characteristic of only animal cells.
Unlike in plants, there is more variety in cells with reference to shapes and functions.
Also, please be aware of a regular cell’s components and cell organelles before proceeding further.
Animal Cell Facts
1. Lack of nucleus
- Animal cells are eukaryotic and have a prominent nucleus.
- But, interestingly, not all cells have a nucleus in them.
For example, red blood cells have no nucleus. Hence, they are called red blood corpuscles instead of cells.
- These RBC cells do not have a nucleus and hence, they cannot multiply by mitosis or meiosis. Instead, they are formed in large number from the bone marrow tissue.
- Also, the hemoglobin inside them occupies most of the space.
- Besides the nucleus, RBCs also lack mitochondria and other cell organelles.
- Similarly, in vascular plants, the sieve tube cells lack a nucleus.
- This is the ability of the cells to convert into any other required cell in the body.
- Stem cells are the ones that are totipotent.
- They can be found in newborn babies’ dental growth tissue, placenta, and umbilical cord blood.
- In the body, these stem cells convert into specific organ cells as per that organ’s needs.
- Thus, they help to repair damaged tissue or replace worn-out tissue.
3. Ability to swim
- Some animal cells can swim when required.
- These cells include the protozoans and sperm cells (the male gametes).
- The protozoans can swim with flagella or cilia in water.
- The sperm cells when released into the uterus entrance, swim with their tail all the way in the uterus to fuse with ova (the female gamete).
As seen in the image above, the tail has mitochondrial energy that enables them to swim effectively.
- Most cells have receptors on their plasma membranes.
- Receptors are the structures that can receive a signal from external stimuli.
- These are protein structures that receive a signal from external agents and convey it into the cell.
- This is how the drugs act at the cellular level and bring the required effects.
Based on their mechanism, there are four types of receptors in animal bodies with diverse functions.
5. Life span is decided by Telomer
- Telomeres are considered to decide the lifespan. They are repetitive nucleotide sequences present at the end of each chromosome.
- These protect the ends of the chromosome from damage and abnormal fusion with other chromosomes.
- As you are aware, the cell divides by the processes of mitosis and multiplies in numbers.
- For each cell division, the telomere length goes down, and it decides the lifespan of a cell.
- As per the Hayflick limit, a cell can undergo approximately 40 to 60 divisions by mitosis.
- Then, it goes for the senescence phase and dies by programmed cell death.
- Cell life also depends on stress, health, nutrition, and other conditions.
- During the process of physiology and daily life activities, the cell tends to have some malfunctions.
- This happens in terms of abnormalities in DNA strand, RNA strand, protein arrangement, etc.
- But, of them, DNA repair is crucial and happens almost every day.
- The cells immediately correct the malfunction for their stability.
If unable to correct, they go for self-destruction.
- As mentioned before, cells can trigger death on themselves.
- When a cell is injured, or faulty DNA is formed during cell division, they go for self-destruction to avoid damage to other cells.
8. Lack of cell division
- Animal cells replicate either through mitosis or meiosis to increase the numbers needed for repair, wound healing, and maintenance.
- But nerve cells are an exception to this phenomenon of replication.
- They never divide or multiply once formed during birth.
- If there is damage, they try to innervate the surrounding area by the process called nerve plasticity.
9. Chemotaxis activity
- This is a mechanism by which the cells move towards one part of the body based on chemical signals.
- This is seen in the case of white blood cells.
- When there is an infection or wound in one part of the body, the WBC cells migrate to that point for defense and repair.
- Hence you will notice pus in the area of wounds, infections, or cancers.
- The intention of migration is to kill the pathogens, produce histamine, and enhance the repair process.
- Haven’t you noticed the sense of itch at the point of the wound during healing? This is due to the histamine released by WBCs.
10. Cell eating
- In general, the cells absorb the nutrients provided by blood circulation.
- But, few animal cells can eat solid matter by themselves by a process called phagocytosis.
- Macrophages and neutrophils are the type of white blood cells that engulf any harmful bacteria or toxins in the body.
- This cell eating is called phagocytosis. Neutrophils eat any harmful bacteria present in the blood circulation.
- While the macrophages engulf any pathogenic microbes in the tissues.
- Once eaten by these cells, the microbes are digested by the enzymatic action of lysosomes.
11. Cell drinking
A cell can also drink liquid material or substances by a process known as pinocytosis.
This is seen primarily in protozoa like the amoeba.
Rod cells and cone cells are present in the eye to help in vision.
They have a protein called photoreceptor protein which absorbs the photons of light and induces changes in the membrane potential.
Rod cells are very sensitive in that a single photon of light can trigger them.
Cats have six to eight times more rods than humans.
Due to this, they can see in the dark, unlike us.
On the other hand, insects have compound eyes and multiple visions. So, a single object appears as numerous objects to them.
13. Organelle location
The location of organelles varies based on the requirement of other factors.
The mitochondria are concentrated at the nerve endings in nerve cells to generate the energy required for signal transduction.
14. Cell content
Almost 70% of cell matter is made of water; the remaining consists of proteins, carbohydrates, lipids, micro-elements, etc.
Frequently asked questions and answers
The cell organelles that permit sperm cells to move are?
The sperm tail helps in movement. But the energy for it is generated by mitochondria.
Why don’t animal cells have cell walls?
Plants and bacteria are non-motile and require cell wall as a protection mechanism.
Where as animal cells like amoeba can move and have movability as a feature instead of cellwall for protection.
Are cells smaller than molecules?
No! cells are larger than molecules and cells in general have thousands of molecules in them.