Introduction:
An animal cell is a type of eukaryotic cell that is characteristic of animals. Eukaryotic cells are characterized by the presence of a true nucleus, which contains the cell’s genetic material in the form of DNA.
Animal cells also have several other membrane-bound organelles, such as mitochondria, which are responsible for generating energy for the cell, and lysosomes, which contain enzymes that help to break down and recycle materials.
Animal cells are typically smaller and more rounded in shape than plant cells, and they are not surrounded by a cell wall.
They can be found in a variety of tissues and organs throughout the body, and they play a variety of roles in the body, including providing structure, aiding in movement, and carrying out various functions necessary for the organism’s survival.
Size and shape:
The size and shape of an animal cell can vary significantly depending on the type of cell and the organism it belongs to. In general, animal cells are smaller than plant cells and can range in size from about 10 micrometers (μm) to 100 μm in diameter. For comparison, a human hair is about 100,000 μm in diameter, so animal cells are typically much smaller than visible to the naked eye.
There are also many factors that can influence the size of an animal cell, such as the organism’s size and the cell’s function. For example, cells that are involved in movement, such as muscle cells, tend to be longer and slenderer in shape than other types of cells. Additionally, cells that are involved in the synthesis of large amounts of proteins or other biomolecules may be larger than other types of cells.
Despite their small size, animal cells are highly complex and contain a wide variety of organelles and structures that are essential for the proper functioning of the cell and the organism as a whole.
Structure:
Some of the main organelles found in animal cells include:
Nucleus: It is a membrane-bound organelle found in eukaryotic cells. It is the central control center of the cell and contains the cell’s genetic material in the form of DNA. The nucleus is separated from the cytoplasm by a double-layered membrane called the nuclear envelope, which is perforated by nuclear pores that allow substances to pass in and out of the nucleus.
The main function of the nucleus is to store and replicate the cell’s DNA and to transcribe the DNA into RNA, which is then used to synthesize proteins. The nucleus also plays a key role in cell division, coordinating the separation of the cell’s genetic material into two new daughter cells.
Fig: Structural overview of animal cell
The nucleus is typically spherical in shape and is typically the largest organelle in the cell. In addition to DNA, the nucleus also contains a variety of other structures, such as chromatin, nucleoli, and nuclear pores. These structures help to organize and regulate the cell’s genetic material and play a key role in the cell’s functions.
Mitochondria: Mitochondria are organelles found in eukaryotic cells that are responsible for generating energy for the cell through the process of cellular respiration. They have a double-layered membrane and contain their own DNA.
Mitochondria are important for several reasons. First, they produce the majority of the cell’s ATP, which is the primary source of energy for the cell’s activities. Second, they play a key role in cell signaling, regulation of the cell cycle, and programmed cell death. Finally, mitochondria are involved in the synthesis of certain biomolecules, such as lipids and steroids.
Mitochondria are found in most eukaryotic cells, including animal cells and plant cells. They vary in size and shape depending on the cell type and the organism they belong to. In general, mitochondria are more numerous in cells that have high energy demands, such as muscle cells and nerve cells.
Overall, mitochondria are essential for the proper functioning of the cell and are a vital part of the complex systems that keep us alive and healthy.
Fig: Mitochondria Structure Animal Cell
Endoplasmic reticulum (ER) and Golgi apparatus: The endoplasmic reticulum (ER) and the Golgi apparatus are organelles found in eukaryotic cells that are involved in the synthesis, modification, and transport of proteins and lipids.
The endoplasmic reticulum (ER) is a network of flattened sacs and tubes that is found throughout the cytoplasm of eukaryotic cells. It is divided into two main regions: the smooth endoplasmic reticulum (SER) and the rough endoplasmic reticulum (RER). The SER is involved in the synthesis of lipids, while the RER is involved in the synthesis and modification of proteins. The RER is studded with ribosomes, which are small organelles that are involved in protein synthesis.
The Golgi apparatus, also known as the Golgi complex or Golgi body, is a stack of flattened membranous sacs that is found near the nucleus of eukaryotic cells. It is involved in sorting, modifying, and distributing proteins and lipids that are synthesized in the cell. The Golgi apparatus receives proteins and lipids from the ER and modifies them through a series of chemical reactions. It then sorts the modified proteins and lipids into vesicles and transports them to their final destination within the cell or to other cells.
Overall, the ER and the Golgi apparatus play a vital role in the synthesis, modification, and transport of proteins and lipids within the cell and are essential for the proper functioning of the cell.
Fig: Nucleus & Endoplasmic Reticulum Structure
Ribosomes: Ribosomes are small organelles found in the cytoplasm of eukaryotic cells that are responsible for synthesizing proteins. They are made up of ribosomal RNA (rRNA) and proteins and are composed of two subunits: the large subunit and the small subunit.
Ribosomes function by translating the genetic code from RNA into proteins. This process, known as protein synthesis, involves the transcription of DNA into RNA and the subsequent translation of the RNA code into a sequence of amino acids, which are the building blocks of proteins. The sequence of amino acids is determined by the specific sequence of nucleotides in the RNA molecule.
Ribosomes are found in many types of cells, including animal cells, plant cells, and bacterial cells. They can be found in the cytoplasm of the cell or attached to the endoplasmic reticulum (ER). Ribosomes are essential for the proper functioning of the cell and are a vital part of the complex systems that keep us alive and healthy.
Lysosomes: Lysosomes are small, spherical organelles found in eukaryotic cells that contain a variety of hydrolytic enzymes that are capable of breaking down a wide range of biomolecules, including carbohydrates, lipids, nucleic acids, and proteins. They are formed from the Golgi apparatus and are usually about 0.1 to 1.2 micrometers (μm) in diameter.
Lysosomes have several important functions within the cell. First, they play a key role in the degradation of materials that have been brought into the cell through endocytosis, a process by which the cell takes in material from its environment. Second, lysosomes are involved in the degradation of damaged or unnecessary cellular components, a process known as autophagy. Finally, lysosomes are involved in the disposal of waste products within the cell.
Lysosomes are found in most eukaryotic cells, including animal cells and plant cells. They are essential for the proper functioning of the cell and are a vital part of the complex systems that keep us alive and healthy.
Centrioles: Centrioles are tiny, cylindric organelles that play a role in cell division in eukaryotic cells. They normally measure between 0.1 and 0.2 micrometers (m) in diameter and 0.2 to 0.5 micrometers (m) in length and are composed of microtubules. Animal cells include centrioles, but neither plant nor fungal cells do.
During cell division, centrioles assist in assembling the microtubules of the cell into the mitotic spindle, a structure that aids in separating the chromosomes of the cell during mitosis. Additionally, cilia and flagella, which are whip-like structures that assist cells in moving or sensing their surroundings, are formed by centrioles.
Centrioles are usually found in pairs, with each pair made up of two centrioles that are at right angles to one other. One centriole in each pair acts as a template for the development of a new centriole during cell division, while the other centriole remains unmodified.
Further, centrioles are necessary for the normal functioning of the cell and are an important component of the complex systems that keep humans alive and healthy.
Types:
There are many other types of animal cells as well, each of which plays a specific role in the body’s tissues and organs. Despite their diversity, all animal cells are characterized by the presence of a true nucleus and other membrane-bound organelles, and they are essential for the proper functioning of the body. There are many different types of animal cells, each of which is specialized to perform a specific function within the body. Some examples of different types of animal cells include:
Epithelial cells: These cells form the outer layer of skin and line the inside of organs and blood vessels. They are closely packed together and are involved in protection, absorption, and secretion.
Endothelial cells: Endothelial cells are specialized cells that form the lining of blood
Nerve cells: Also known as neurons, these cells are specialized for transmitting signals throughout the body. They have long, thin extensions called axons that carry electrical signals from one part of the cell to another.
Fig: Different types of animal cells
Muscle cells: There are three types of muscle cells: skeletal, smooth, and cardiac. Skeletal muscle cells are responsible for movement and are controlled by the brain, while smooth muscle cells are found in the walls of organs and are involved in regulating blood flow and movement of substances through the body. Cardiac muscle cells are found in the heart and are responsible for pumping blood throughout the body.
Blood cells: Blood cells are specialized cells that are found in the blood and are involved in various functions, such as carrying oxygen to the body’s tissues and defending the body against infection. There are three main types of blood cells: red blood cells, which carry oxygen; white blood cells, which defend the body against infection; and platelets, which help to stop bleeding.
Stem cells: These are undifferentiated cells that can develop into a variety of cell types. They are necessary for tissue repair and maintenance.
Functions:
Animal cells perform a wide variety of functions that are essential for the proper functioning of the body. They are essential for the proper functioning of the body and are a vital part of the complex systems that keep us alive and healthy.
Providing structure: Many types of animal cells, such as epithelial cells and muscle cells, provide structure and support to the body’s tissues and organs.
Aiding in movement: Cells such as muscle cells and nerve cells are involved in movement, both within the body and at the cellular level.
Carrying out metabolic reactions: Animal cells are the site of many important chemical reactions, such as the breakdown of nutrients to produce energy and the synthesis of various biomolecules.
Communicating with other cells: Cells communicate with each other through various signaling pathways, and this communication is essential for coordinating the body’s functions.
Maintaining homeostasis: Homeostasis is the maintenance of a stable internal environment within the body, and animal cells play a key role in this process. For example, cells involved in the immune system help to defend the body against infections, while cells involved in the endocrine system help to regulate the body’s hormones and other signaling molecules.
Repairing and regenerating tissues: Many types of animal cells, including stem cells, have the ability to regenerate and repair damaged tissues.
Differentiate animal and plant cell:
Animal cells and plant cells are both types of eukaryotic cells, which are characterized by the presence of a true nucleus and other membrane-bound organelles. In general, animal cells and plant cells are similar in many ways, but they also have several key differences that reflect their specialized functions within the body.
However, there are several key differences between animal cells and plant cells:
Size: Plant cells are generally larger than animal cells, with diameters ranging from 10-100 micrometers (μm). Animal cells are typically smaller, with diameters ranging from 10-30 μm.
Shape: Plant cells are often rectangular or square in shape, while animal cells are more rounded or irregular in shape.
Cell wall: Plant cells are surrounded by a rigid cell wall made up of cellulose, while animal cells do not have a cell wall.
Chloroplasts: Plant cells contain chloroplasts, which are organelles that are involved in photosynthesis, the process by which plants convert sunlight into energy. Animal cells do not contain chloroplasts.
Central vacuole: Plant cells contain a large, fluid-filled organelle called a central vacuole, which helps to maintain the cell’s shape and stores various substances, such as water and pigments. A central vacuole is absent in animal cells.
References:
- Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K. and Walter, P., 2003. Molecular biology of the cell. Scandinavian Journal of Rheumatology, 32(2), pp.125-125.
- Karp, G., 2009. Cell and molecular biology: concepts and experiments. John Wiley & Sons.
- Ganem, D., 1997. The cell: a molecular approach by Geoffrey M. Cooper. NATURE MEDICINE, 3, pp.1042-1042.