We are aware of the fact that the cell is the structural and fundamental unit of life. It is also the smallest and the most basic biological unit of living organisms. Life on planet earth is broadly classified either as unicellular or multicellular.
Animal Cell Definition
Animal cells range in size from a few millimetres to microscopic microns. The largest known animal cell is the ostrich egg, which can stretch over 5.1 inches across and weigh about 1.4 kilograms. This is in stark contrast to the neuron in the human body, which is just 100 microns across.
The shape of animal cells also varies, with some being flat, others oval or rod-shaped. There are also more intriguing shapes such as curved, spherical, concave and rectangular. Most of the cells are microscopic in size and can only be seen under the microscope. Animal cells are eukaryotic cells with a membrane-bound nucleus. Furthermore, these cells exhibit the presence of DNA inside the nucleus. They also comprise of other organelles and cellular structures which carry out specific functions necessary for the cell to function properly.
Animal Cell Structure
Though this animal cell diagram is not representative of any one particular type of cell, it provides insight into the primary organelles and the intricate internal structure of most animal cells. Furthermore, it is easy to distinguish between a plant and animal cell diagram just by inspecting the presence or absence of a cell wall.
Animal Cell Organelles
Animal cells are generally smaller than plant cells. Another defining characteristic is its irregular shape. This is due to the absence of a cell wall. But animal cells share other cellular organelles with plant cells as both have evolved from eukaryotic cells.
A typical animal cell comprises the following cell organelles:
Cell Membrane: A thin semipermeable membrane layer of protein and fats surrounding the cell. Its primary role is to protect the cell from its surrounding. Also, it controls the entry and exit of nutrients and other microscopic entities into the cell.
Nuclear Membrane: It is a double-membraned structure that surrounds the nucleus. It is also referred to as the nuclear envelope.
Nucleus: It is an organelle that contains several other sub-organelles such as nucleolus, nucleosomes and chromatins. It also contains DNA and other genetic materials.
Centrosome: It is a small organelle found near to the nucleus which has a thick centre with radiating tubules. The centrosomes are where microtubules are produced.
Lysosome (Cell Vesicles): They are round organelle surrounded by a membrane comprising of digestive enzymes which help in digestion, excretion and in the cell renewal process.
Cytoplasm: A jelly-like material which contains all the cell organelles, enclosed within the cell membrane. The substance found within the cell nucleus, contained by the nuclear membrane is called the nucleoplasm.
Golgi Apparatus: A flat, smooth layered, sac-like organelle which is located near the nucleus and involved in manufacturing, storing, packing and transporting the particles throughout the cell.
Detailed Reading: Golgi Apparatus
Mitochondrion: They are spherical or rod-shaped organelles with a double membrane. They are the powerhouse of a cell as they play an important role in releasing energy.
Ribosome: They are small organelles made up of RNA-rich cytoplasmic granules and they are the sites of protein synthesis.
- Endoplasmic Reticulum (ER): This cellular organelle is composed of a thin, winding network of membranous sacs originating from the nucleus.
Vacuole: A membrane-bound organelles present inside a cell involved in maintaining shape and storing water, food, wastes, etc.
Nucleopore: They are tiny holes present in the nuclear membrane which are involved in the movement of nucleic acids and proteins within the cell.
Animal Cell Types
There are numerous types of animal cells, each designed to serve specific functions. The most common types of animal cells are:
- Skin Cells: Melanocytes, keratinocytes, Merkel cells and Langerhans cells
- Muscle Cells: Myocyte, Myosatellite cells, Tendon cells, Cardiac muscle cells
- Blood Cells: Leukocytes, erythrocytes, platelet
- Nerve cells: Schwann cell, glial cells etc
- Fat Cells: Adipocytes
Points to Note About Animal Cell
The cell is the structural and functional unit of life. These cells differ in their shapes, sizes and their structure as they have to fulfil specific functions. Plant cells and animal cells share some common features as both are eukaryotic cells. However, the major difference ends there as animals need to adapt to a more active and non-sedentary lifestyle. Furthermore, animals need to acquire their own food, therefore, they do not possess any of the specialized cell organelles such as chloroplasts.
Important Questions about Animal Cell
1. What is an animal cell?
As the name implies, an animal cell is a type of cell that is seen specifically in animal tissues. It is characterized by the absence of a cell wall, with cell organelles enclosed within the cell membrane.
2. Name the cell organelle that contains the genetic material of the cell.
3. Which cell organelle is responsible for the generation of energy for cellular activities?
4. Name the double-layered membrane responsible for enveloping the nucleus.
5. What is the role of lysosomes?
Lysosomes help in digestion, excretion and cell renewal process
6. State the various types of animal cells.
- Skin Cells
- Muscle Cells
- Blood Cells
- Nerve cells
- Fat Cells
7. Explain how an animal cell varies from a plant cell.
An animal cell is usually irregular and round in shape. This is primarily due to the absence of the cell wall, which is a characteristic feature of plant cells. Furthermore, animal cells do not plastids as animals are not autotrophs.
8. Name the selectively permeable structure that envelopes the entire cell.
9. Which cell organelle is responsible for packing?
Animal Cell is a fundamental topic taught in class 9 and higher. To find more animal cell information or other related topics, please explore BYJU’S Biology.